- New L-dopa codrugs as potential antiparkinson agents
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This paper reports the synthesis and preliminary evaluation of new L-dopa (LD) conjugates (1 and 2) obtained by joining LD with two different natural antioxidants, caffeic acid and carnosine, respectively. The antioxidant efficacy of compounds 1 and 2 was
- Sozio, Piera,Iannitelli, Antonio,Cerasa, Laura Serafina,Cacciatore, Ivana,Cornacchia, Catia,Giorgioni, Gianfabio,Ricciutelli, Massimo,Nasuti, Cinzia,Cantalamessa, Franco,Di Stefano, Antonio
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- Detection of tyrosine and monitoring tyrosinase activity using an enzyme cascade-triggered colorimetric reaction
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The aromatic amino acid tyrosine is an essential precursor for the synthesis of catecholamines, including l-DOPA, tyramine, and dopamine. A number of metabolic disorders have been linked to abnormal tyrosine levels in biological fluids. In this study, we developed an enzyme cascade-triggered colorimetric reaction for the detection of tyrosine, based on the formation of yellow pigment (betalamic acid) and red fluorometric betaxanthin. Tyrosinase converts tyrosine to l-DOPA, and DOPA-dioxygenase catalyzes oxidative cleavage of l-DOPA into betalamic acid. Response is linear for tyrosine from 5 to 100 μM, and the detection limit (LOD) is 2.74 μM. The enzyme cascade reaction was applied to monitor tyrosinase activity and tyrosinase inhibition assays. Lastly, the performance of the proposed biosensor proved successful in the analysis of urine samples without the need for pre-treatment. This journal is
- Chen, Huei-Yu,Yeh, Yi-Chun
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- Immobilization of polyphenol oxidase onto mesoporous activated carbons - isotherm and kinetic studies
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Investigations were carried out in batch modes for studying the immobilization behavior of polyphenol oxidase (PPO) on two different mesoporous activated carbon matrices, MAC400 and MAC200. The PPO was immobilized onto MAC400 and MAC200 at various enzyme activities 5 × 104, 10 × 104, 20 × 104, 30 × 104 U l-1, at pH 5-8, and at temperature ranging from 10 to 40 °C. The intensity of immobilization of PPO increased with increase in temperature and initial activities, while it decreased with increase in pH. Immobilization onto MAC400 followed the Langmuir model while Langmuir and Freundlich models could fit MAC200 data. Non-linear pseudo first order, pseudo second order and intraparticle diffusion models were evaluated to understand the mechanism of immobilization. The free and immobilized enzyme kinetic parameters (Km and Vmax) were determined by Michaelis-Menten enzyme kinetics. The Km values for free enzyme, PPO immobilized in MAC400 and in MAC200 were 0.49, 0.41 and 0.65 mM, respectively. The immobilization of PPO in carbon matrices was confirmed using FT-IR spectroscopy and scanning electron microscopy.
- John Kennedy,Selvi,Aruna Padmanabhan,Hema,Sekaran
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- Measurement of intrinsic rate constants in the tyrosine hydroxylase reaction
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Tyrosine hydroxylase (TyrH) is a pterin-dependent mononuclear non-heme aromatic amino acid hydroxylase that catalyzes the conversion of tyrosine to dihydroxyphenylalanine (DOPA). Chemical quench analyses of the enzymatic reaction show a burst of DOPA formation, followed by a linear rate equal to the kcat value at both 5 and 30 °C. The effects of increasing solvent viscosity confirm that kcat is ～84% limited by diffusion, most probably due to slow product release, and that tyrosine has a commitment to catalysis of 0.45. The effect of viscosity on the kcat/Km for 6-methyltetrahydropterin is greater than the theoretical limit, consistent with the coupling of pterin binding to the movement of a surface loop. The absorbance changes in the spectrum of the tetrahydropterin during the first turnover, the kinetics of DOPA formation during the first turnover, and the previously described kinetics for formation and decay of the Fe(IV)O intermediate [Eser, B. E., Barr, E. W., Frantom, P. A., Saleh, L., Bollinger, J. M., Jr., Krebs, C., and Fitzpatrick, P. F. (2007) J. Am. Chem. Soc. 129, 11334-11335] were analyzed globally, yielding a single set of rate constants for the TyrH reaction. Reversible binding of oxygen is followed by formation of Fe(IV)O and 4a-hydroxypterin with a rate constant of 13 s-1 at 5 °C. Transfer of oxygen from Fe(IV)O to tyrosine to form DOPA follows with a rate constant of 22 s-1. Release of DOPA and/or the 4a-hydroxypterin with a rate constant of 0.86 s-1 completes the turnover.
- Eser, Bekir E.,Fitzpatrick, Paul F.
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- Reductase-catalyzed tetrahydrobiopterin regeneration alleviates the anti-competitive inhibition of tyrosine hydroxylation by 7,8-dihydrobiopterin
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l-Tyrosine hydroxylation by tyrosine hydroxylase is a significant reaction for preparing many nutraceutical and pharmaceutical chemicals. Two major challenges in constructing these pathways in bacteria are the improvement of hydroxylase catalytic efficiency and the production of cofactor tetrahydrobiopterin (BH4). In this study, we analyzed the evolutionary relationships and conserved protein sequences between tyrosine hydroxylases from different species by PhyML and MAFFT. Finally, we selected 7 tyrosine hydroxylases and 6 sepiapterin reductases. Subsequently, the function of different groups was identified by a combined whole-cell catalyst, and a series of novel tyrosine hydroxylase/sepiapterin reductase (TH/SPR) synthesis systems were screened including tyrosine hydroxylase (from Streptosporangium roseum DSM 43021 and Thermomonospora curvata DSM 43183) and sepiapterin reductase (from Photobacterium damselae, Chlorobaculum thiosulfatiphilum and Xenorhabdus poinarii), namely as SrTH/PdSPR, SrTH/CtSPR, SrTH/XpSPR and TcTH/PdSPR, which can synthesize l-Dopa by hydroxylating l-tyrosine in Bacillus licheniformis. Furthermore, we analyzed the characterization of SrTH by enzyme catalysis and demonstrated that 7,8-dihydrobiopterin (BH2) formed by BH4 autooxidation was an anticompetitive inhibitor on SrTH. Finally, pure dihydropteridine reductase from Escherichia coli (EcDHPR) was added to the solution, and l-Dopa could be continually synthesized after 3 h, which was improved by 86% at 6 h in the catalytic reaction by SrTH. This indicates that BH4 regeneration can alleviate the inhibition by BH2 during tyrosine hydroxylation. This study provides a good starting point and theoretical foundation for further modification to improve the catalytic efficiency of tyrosine hydroxylation by tyrosine hydroxylase.
- Ding, Zhongyang,Li, Leyun,Li, Youran,Shi, Guiyang,Xu, Yinbiao,Zhang, Liang
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- Novel strategy for enhancing productivity in l-DOPA synthesis: The electroenzymatic approach using well-dispersed l-tyrosine
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Although l-DOPA (l-3,4-dihydroxyphenylalanine) is widely used as a drug for Parkinson's disease, there are critical drawbacks in the commercial synthetic method such as low conversion rate, poor productivity, and long operational time. In order to overcome these limitations, a novel electroenzymatic system using tyrosinase/carbon nanopowder/polypyrrole composite as a working cathode was reported with the outstanding conversion rate up to 95.9%. However, the productivity was still limited due to a low solubility of the substrate l-tyrosine in aqueous phase. Herein, we demonstrated a novel strategy for enhancing the productivity by employing well-dispersed l-tyrosine as the substrate. When using well-dispersed l-tyrosine, not only the concentration of the substrate was increased to 90.6 gL-1 in aqueous phase but also the productivity was enhanced up to 15.3 gL-1 h-1. We also determined kinetic parameters in the electroenzymatic system and the kinetic results revealed that the outstanding conversion rate was based on the fast electrical reduction of the by-product to l-DOPA. Thus the electroenzymatic synthesis using well-dispersed l-tyrosine can be a potential candidate as a novel process for l-DOPA synthesis.
- Min, Kyoungseon,Kathavarayan, Thenmozhi,Park, Kyungmoon,Yoo, Young Je
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- Histidine residues at the copper-binding site in human tyrosinase are essential for its catalytic activities
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Tyrosinase is a copper-binding enzyme involved in melanin biosynthesis. However, the detailed structure of human tyrosinase has not yet been solved, along with the identification of the key sites responsible for its catalytic activity. We used site-directed mutagenesis to identify the residues critical for the copper binding of human tyrosinase. Seven histidine mutants in the two copper-binding sites were generated, and catalytic activities were characterised. The tyrosine hydroxylase activities of the CuA site mutants were approximately 50% lower than those of the wild-type tyrosinase, while the dopa oxidation activities of the mutants were not significantly different from that of wild-type tyrosinase. By contrast, mutations at CuB significantly decreased both tyrosine hydroxylation and dopa oxidation activities, confirming that the catalytic sites for these two activities are at least partially distinct. These findings provide a useful resource for further structural determination and development of tyrosinase inhibitors in the cosmetic and pharmaceutical industries.
- Choi, Hye Won,Hong, Sungguan,Jo, Hyun-Joo,Kong, Kwang-Hoon,Lee, Sung Jun,Noh, Hyangsoon
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- Daedalin A, a metabolite of daedalea dickinsii, inhibits melanin synthesis in an in vitro human skin model
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The culture broth of Daedalea dickinsii was found to predominantly contain the tyrosinase inhibitor, (2R)-6- hydroxy-2-hydroxymethyl-2-methyl-2H-chromene, daedalin A (1). Ongoing research into bioactive metabolites resulted in the identification of two new 2H-chromenes, 6-hydroxy-5,7-dimethoxy-2,2-dimethyl-2H- chromene (3) and 6-hydroxy-2-hydroxymethyl-5-methoxy-2-methyl- 2H-chromene (4), together with 6-hydroxy-2,2-dimethyl- 2H-chromene (2). Comparative studies of isolated compounds 1-4 and related compounds (±)-1 and 1a-1c showed 1 to have the strongest tyrosinase inhibitory activity. These results suggest that the hydroxyl groups at positions 6 and 9 of 1 were important for the potent activity. A Lineweaver-Burk plot for a kinetic analysis indicates that 1 competed with L-tyrosine for tyrosinase. Compound 1 also suppressed melanogenesis in a human skin model (up to 49% at 2.8μmol/tissue application) without affecting the cell viability. Compounds 1, 1b and 1c also showed 1,1- diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity comparable to that of α-tocopherol.
- Morimura, Keiji,Hiramatsu, Kenji,Yamazaki, Chihiro,Hattori, Yasunao,Makabe, Hidefumi,Hirota, Mitsuru
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- Singlet oxygen-mediated protein oxidation: Evidence for the formation of reactive side chain peroxides on tyrosine residues
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Singlet oxygen (1O2) is generated by a number of enzymes as well as by UV or visible light in the presence of a sensitizer and has been proposed as a damaging agent in a number of pathologies including cataract, sunburn, and skin can
- Wright, Adam,Bubb, William A.,Hawkins, Clare L.,Davies, Michael J.
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- Pulsed EPR study of amino acid and tetrahydropterin binding in a tyrosine hydroxylase nitric oxide complex: Evidence for substrate rearrangements in the formation of the oxygen-reactive complex
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Tyrosine hydroxylase is a nonheme iron enzyme found in the nervous system that catalyzes the hydroxylation of tyrosine to form l-3,4- dihydroxyphenylalanine, the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters. Catalysis requires the binding of three substrates: tyrosine, tetrahydrobiopterin, and molecular oxygen. We have used nitric oxide as an O2 surrogate to poise Fe(II) at the catalytic site in an S = 3/2, {FeNO}7 form amenable to EPR spectroscopy. 2H-electron spin echo envelope modulation was then used to measure the distance and orientation of specifically deuterated substrate tyrosine and cofactor 6-methyltetrahydropterin with respect to the magnetic axes of the {FeNO}7 paramagnetic center. Our results show that the addition of tyrosine triggers a conformational change in the enzyme that reduces the distance from the {FeNO}7 center to the closest deuteron on 6,7-2H-6-methyltetrahydropterin from >5.9 A to 4.4 ± 0.2 A. Conversely, the addition of 6-methyltetrahydropterin to enzyme samples treated with 3,5-2H-tyrosine resulted in reorientation of the magnetic axes of the S = 3/2, {FeNO}7 center with respect to the deuterated substrate. Taken together, these results show that the coordination of both substrate and cofactor direct the coordination of NO to Fe(II) at the active site. Parallel studies of a quaternary complex of an uncoupled tyrosine hydroxylase variant, E332A, show no change in the hyperfine coupling to substrate tyrosine and cofactor 6-methyltetrahydropterin. Our results are discussed in the context of previous spectroscopic and X-ray crystallographic studies done on tyrosine hydroxylase and phenylalanine hydroxylase.
- Krzyaniak, Matthew D.,Eser, Bekir E.,Ellis, Holly R.,Fitzpatrick, Paul F.,McCracken, John
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- Self-assembled adhesive biomaterials formed by a genetically designed fusion protein
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Here we report a recombinant protein (MS) obtained by genetic fusion of a mussel foot protein (Mfp3) motif into a silk spidroin (MaSp1). The MS not only self-assembled into a supramolecular fibre, as does the parent MaSp1, but also showed enhanced adhesiveness resulting from the DOPA-containing Mfp3 portion. The successful incorporation of the wet adhesiveness of Mfp3 into the well-structured assembly of MaSp1 may provide a new insight for the genetic design of underwater adhesive recombinant proteins by utilizing the structural features of a spidroin protein.
- Aich, Pulakesh,An, Jaeyeon,Yang, Byeongseon,Ko, Young Ho,Kim, Junghyun,Murray, James,Cha, Hyung Joon,Roh, Joon Ho,Park, Kyeng Min,Kim, Kimoon
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- High-throughput assay of tyrosine phenol-lyase activity using a cascade of enzymatic reactions
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Tyrosine phenol-lyase (TPL) exhibits great potential in industrial biosynthesis of L-tyrosine and its derivates. To uncover and screen TPLs with excellent catalytic properties, there is unmet demand for development of facile and reliable screening system for TPL. Here we presented a novel assay format for the detection of TPL activity based on catechol 2,3-dioxygenase (C23O)-catalyzed reaction. Catechol released from TPL-catalyzed cleavage of 3,4-dihydroxy-L-phenylalanine (L-DOPA) was further oxidized by C23O to form 2-hydroxymuconate semialdehyde, which could be readily detected by spectrophotometric measurements at 375 nm. The assay achieved a unique balance between the ease of operation and superiority of analytical performances including linearity, sensitivity and accuracy. In addition, this assay enabled real-time monitoring of TPL activity with high efficiency and reliability. As C23O is highly specific towards catechol, a non-natural product of microorganism, the assay was therefore accessible to both crude cell extracts and the whole-cell system without elaborate purification steps of enzymes, which could greatly expedite discovery and engineering of TPLs. This study provided fundamental principle for high-throughput screening of other enzymes consuming or producing catechol derivatives.
- Zhu, Hang-Qin,Hu, Wen-Ye,Tang, Xiao-Ling,Zheng, Ren-Chao,Zheng, Yu-Guo
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- Highly Stable Zr(IV)-Based Metal-Organic Frameworks for Chiral Separation in Reversed-Phase Liquid Chromatography
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Separation of racemic mixtures is of great importance and interest in chemistry and pharmacology. Porous materials including metal-organic frameworks (MOFs) have been widely explored as chiral stationary phases (CSPs) in chiral resolution. However, it remains a challenge to develop new CSPs for reversed-phase high-performance liquid chromatography (RP-HPLC), which is the most popular chromatographic mode and accounts for over 90% of all separations. Here we demonstrated for the first time that highly stable Zr-based MOFs can be efficient CSPs for RP-HPLC. By elaborately designing and synthesizing three tetracarboxylate ligands of enantiopure 1,1′-biphenyl-20-crown-6, we prepared three chiral porous Zr(IV)-MOFs with the framework formula [Zr6O4(OH)8(H2O)4(L)2]. They share the same flu topological structure but channels of different sizes and display excellent tolerance to water, acid, and base. Chiral crown ether moieties are periodically aligned within the framework channels, allowing for stereoselective recognition of guest molecules via supramolecular interactions. Under acidic aqueous eluent conditions, the Zr-MOF-packed HPLC columns provide high resolution, selectivity, and durability for the separation of a variety of model racemates, including unprotected and protected amino acids and N-containing drugs, which are comparable to or even superior to several commercial chiral columns for HPLC separation. DFT calculations suggest that the Zr-MOF provides a confined microenvironment for chiral crown ethers that dictates the separation selectivity.
- Jiang, Hong,Yang, Kuiwei,Zhao, Xiangxiang,Zhang, Wenqiang,Liu, Yan,Jiang, Jianwen,Cui, Yong
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supporting information
p. 390 - 398
(2021/01/13)
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- A novel catalytic heme cofactor in SfmD with a single thioether bond and abis-His ligand set revealed by ade novocrystal structural and spectroscopic study
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SfmD is a heme-dependent enzyme in the biosynthetic pathway of saframycin A. Here, we present a 1.78 ? resolutionde novocrystal structure of SfmD, which unveils a novel heme cofactor attached to the protein with an unusualHxnHxxxCmotif (n～ 38). This heme cofactor is unique in two respects. It contains a single thioether bond in a cysteine-vinyl link with Cys317, and the ferric heme has two axial protein ligands,i.e., His274 and His313. We demonstrated that SfmD heme is catalytically active and can utilize dioxygen and ascorbate for a single-oxygen insertion into 3-methyl-l-tyrosine. Catalytic assays using ascorbate derivatives revealed the functional groups of ascorbate essential to its function as a cosubstrate. Abolishing the thioether linkage through mutation of Cys317 resulted in catalytically inactive SfmD variants. EPR and optical data revealed that the heme center undergoes a substantial conformational change with one axial histidine ligand dissociating from the iron ion in response to substrate 3-methyl-l-tyrosine binding or chemical reduction by a reducing agent, such as the cosubstrate ascorbate. The labile axial ligand was identified as His274 through redox-linked structural determinations. Together, identifying an unusual heme cofactor with a previously unknown heme-binding motif for a monooxygenase activity and the structural similarity of SfmD to the members of the heme-based tryptophan dioxygenase superfamily will broaden understanding of heme chemistry.
- Shin, Inchul,Davis, Ian,Nieves-Merced, Karinel,Wang, Yifan,McHardy, Stanton,Liu, Aimin
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p. 3984 - 3998
(2021/04/06)
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- Genetically encoded dihydroxyphenylalanine coupled with tyrosinase for strain promoted labeling
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Protein modifications through genetic code engineering have a remarkable impact on macromolecule engineering, protein translocation, protein–protein interaction, and cell biology. We used the newly developed molecular biology approach, genetic code engineering, for fine-tuning of proteins for biological availability. Here, we have introduced 3, 4-dihydroxy-L-phenylalanine in recombinant proteins by selective pressure incorporation method for protein-based cell labeling applications. The congener proteins treated with tyrosinase convert 3, 4-dihydroxy-L-phenylalanine to dopaquinone for strain-promoted click chemistry. Initially, the single-step Strain-Promoted Oxidation-Controlled Cyclooctyne-1,2-quinone Cycloaddition was studied using tyrosinase catalyzed congener protein and optimized the temporally controlled conjugation with (1R,8S,9s)-Bicyclo[6.1.0]non-4-yn-9-ylmethanol. Then, the feasibility of tyrosinase-treated congener annexin A5 with easily reactive quinone functional moiety was conjugated with fluorescent tag dibenzocyclooctyne-PEG4-TAMRA for labeling of apoptotic cells. Thus, the congener proteins-based products demonstrate selective cell labeling and apoptosis detection in EA.hy926 cells even after the protein modifications. Hence, genetic code engineering can be coupled with click chemistry to develop various protein-based fluorescent labels.
- George, Augustine,Indhu, Mohan,Ashokraj, Sundarapandian,Shanmugam, Ganesh,Ganesan, Ponesakki,Kamini, Numbi Ramudu,Ayyadurai, Niraikulam
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supporting information
(2021/11/08)
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- Mechanistically Guided One Pot Synthesis of Phosphine-Phosphite and Its Implication in Asymmetric Hydrogenation
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Although hybrid bidentate ligands are known to yield highly enantioselective products in asymmetric hydrogenation (AH), synthesis of these ligands is an arduous process. Herein, a one pot, atom-economic synthesis of a hybrid phosphine-phosphite (L1) is reported. After understanding the reactivity difference between an O-nucleophile versus C-nucleophile, one pot synthesis of Senphos (L1) was achieved (72 %). When L1 was treated with [Rh], 31P NMR revealed bidentate coordination to Rh. Senphos, in the presence of rhodium, catalyzes the AH of Methyl-2-acetamido-3-phenylacrylate and discloses an unprecedented turn over frequency of 2289, along with excellent enantio-selectivity (92 %). The generality is demonstrated by hydrogenating an array of alkenes. The AH operates under mild conditions of 1–2 bar H2 pressure, at room temperature. The practical relevance of L1 is demonstrated by scaling-up the reaction to 1 g and by synthesizing DOPA, a drug widely employed for the treatment of Parkinson's disease. Computational insights indicate that the R isomer is preferred by 3.8 kcal/mol over the S isomer.
- Chikkali, Samir H.,Kumar, Pawan,Kumar, Rohit,Pandey, Swechchha,Sen, Anirban,Vanka, Kumar,Vipin Raj, K.
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- Biocascade Synthesis of L-Tyrosine Derivatives by Coupling a Thermophilic Tyrosine Phenol-Lyase and L-Lactate Oxidase
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A one-pot biocascade of two enzymatic steps catalyzed by an l-lactate oxidase and a tyrosine phenol-lyase has been successfully developed in the present study. The reaction provides an efficient method for the synthesis of l-tyrosine derivatives, which exhibits readily available starting materials and excellent yields. In the first step, an in situ generation of pyruvate from readily available bio-based l-lactate catalyzed by a highly active l-lactate oxidase from Aerococcus viridans (AvLOX) was developed (using oxygen as oxidant and catalase as hydrogen peroxide removing reagent). Pyruvate thus produced underwent C–C coupling with phenol derivatives as acceptor substrate using specially designed thermophilic tyrosine phenol-lyase mutants from Symbiobacterium toebii (TTPL). Overall, this cascade avoids the high cost and easy decomposition of pyruvate and offered an efficient and environmentally friendly procedure for l-tyrosine derivatives synthesis.
- Jiang, Yiqi,Ju, Shuyun,Li, Guosi,Lian, Jiazhang,Lin, Jianping,Wu, Mianbin,Xue, Hailong,Yang, Lirong
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supporting information
(2020/02/25)
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- SKIN-WHITENING COSMETIC COMPOSITION COMPRISING LACTOBACILLUS RHAMNOSUS LM1011 HAVING IMMUNOSTIMULATING ACTIVITY
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The present invention relates to a cosmetic composition for skin whitening comprising novel Lactobacillus rhamnosus LM1011 as an active ingredient. More specifically, the present invention provides a cosmetic composition for skin whitening, comprising novel Lactobacillus rhamnosus LM1011 as an active ingredient, and reducing melanin production by regulating tyrosinase activity.(AA) L-tyrosine 4-hydroxy-1-phenylalanine(BB) Tyrosinase(CC) L-dopa 1-3,4-dihydroxyphenylalanine(DD) Dehydroascorbic acid(EE) Ascorbic acid(FF) Tyrosinase(GG) Dopaquinone(HH) MelaninCOPYRIGHT KIPO 2020
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Paragraph 0009
(2020/05/13)
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- Inhibitory effects and molecular mechanism on mushroom tyrosinase by condensed tannins isolation from the fruit of Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow
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The structure of extracted condensed tannin (CT) from the fruit of Sour jujube (Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow) and the molecular mechanisms by which CT inhibits the activity of mushroom tyrosinase were investigated. The structure of CT was characterized by high performance liquid chromatography electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The kinetic assays were used to detect inhibition effect, type and mechanism. UV scanning, fluorescence quenching, copper interacting, o-quinone interaction and molecular docking assays were also used to reveal the molecular mechanisms by which CT inhibit tyrosinase. The results showed the structural units of CT containing afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin. Kinetic analysis showed that CT inhibits both the monophenolase and diphenolase activities of tyrosinase and exhibits reversible, mixed type mechanism. The fruit CT interacts primarily with the copper ions and specific amino acid residue (Asn191, Thr203, Ala202, Ser206, Met201, His194, His54, Glu182 and Ile42) in the active site of tyrosinase to disturb oxidation of substrates by tyrosinase. These results suggested the sour jujube fruit is a potential natural source of tyrosinase inhibitors, and has a potential to be used in food preservation, whitening cosmetics.
- Liu, Lu-Lu,Ren, Yuan-Jing,Song, Wei,Wei, Shu-Dong,Yang, Hai-Bo
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p. 1813 - 1821
(2020/11/03)
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- Coumaric acid derivatives as tyrosinase inhibitors: Efficacy studies through in silico, in vitro and ex vivo approaches
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p-Coumaric acid is a known inhibitor of tyrosinase, an enzyme involved in the initial steps of the melanin synthesis in human and other species. However, its low lipophilicity impairs its penetration through skin and efficacy as antimelanogenic agent indeed. Accordingly, this paper reports the assessment of several coumaric acid derivatives as tyrosinase inhibitors and antimelanogenic agents in in vitro, in silico and ex vivo assays. The compounds were designed with modifications in the aromatic and acid moieties of p-coumaric acid, being the coumarate esters the most promising derivatives. The compounds showed higher tyrosinase inhibitory activity (pIC50 3.7–4.2) than the parent acid, being compounds 1d, 1e and 1f the most potent inhibitors. Docking analysis showed that these esters are competitive inhibitors per se, and act independently of a redox mechanism as suggested by DPPH assays. Moreover, the esters showed efficacy in reducing the melanin deposition in human skin fragments at 0.1% concentration, especially compound 1e. In summary, there is an important equilibria between tyrosinase affinity and lipophilicity that must be considered to get effective antimelanogenic agents with adequate permeability in the skin.
- Fernandes, Jo?o Paulo S.,Ferrarini, Márcio,Mercaldi, Vitória Gallo,Nazato, Lucas Idacir Sbrugnera,Padovani, Giovana,Sufi, Bianca da Silva,Varela, Marina Themoteo
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- Design and Use of de novo Cascades for the Biosynthesis of New Benzylisoquinoline Alkaloids
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The benzylisoquinoline alkaloids (BIAs) are an important group of secondary metabolites from higher plants and have been reported to show significant biological activities. The production of BIAs through synthetic biology approaches provides a higher-yielding strategy than traditional synthetic methods or isolation from plant material. However, the reconstruction of BIA pathways in microorganisms by combining heterologous enzymes can also give access to BIAs through cascade reactions. Most importantly, non-natural BIAs can be generated through such artificial pathways. In the current study, we describe the use of tyrosinases and decarboxylases and combine these with a transaminase enzyme and norcoclaurine synthase for the efficient synthesis of several BIAs, including six non-natural alkaloids, in cascades from l-tyrosine and analogues.
- Wang, Yu,Tappertzhofen, Nadine,Méndez-Sánchez, Daniel,Bawn, Maria,Lyu, Boyu,Ward, John M.,Hailes, Helen C.
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supporting information
p. 10120 - 10125
(2019/06/27)
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- Evaluation of the Edman degradation product of vancomycin bonded to core-shell particles as a new HPLC chiral stationary phase
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A modified macrocyclic glycopeptide-based chiral stationary phase (CSP), prepared via Edman degradation of vancomycin, was evaluated as a chiral selector for the first time. Its applicability was compared with other macrocyclic glycopeptide-based CSPs: TeicoShell and VancoShell. In addition, another modified macrocyclic glycopeptide-based CSP, NicoShell, was further examined. Initial evaluation was focused on the complementary behavior with these glycopeptides. A screening procedure was used based on previous work for the enantiomeric separation of 50 chiral compounds including amino acids, pesticides, stimulants, and a variety of pharmaceuticals. Fast and efficient chiral separations resulted by using superficially porous (core-shell) particle supports. Overall, the vancomycin Edman degradation product (EDP) resembled TeicoShell with high enantioselectivity for acidic compounds in the polar ionic mode. The simultaneous enantiomeric separation of 5 racemic profens using liquid chromatography-mass spectrometry with EDP was performed in approximately 3?minutes. Other highlights include simultaneous liquid chromatography separations of rac-amphetamine and rac-methamphetamine with VancoShell, rac-pseudoephedrine and rac-ephedrine with NicoShell, and rac-dichlorprop and rac-haloxyfop with TeicoShell.
- Hellinghausen, Garrett,Lopez, Diego A.,Lee, Jauh T.,Wang, Yadi,Weatherly, Choyce A.,Portillo, Abiud E.,Berthod, Alain,Armstrong, Daniel W.
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p. 1067 - 1078
(2018/08/01)
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- Synthetic method for drug intermediate levodopa
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The invention discloses a synthetic method for the drug intermediate levodopa. The synthetic method comprises the following steps: adding a 2-amino-3-(3-chloro-4-hydroxyphenyl)propionic acid and a sodium nitrate solution into a reaction vessel, controlling a solution temperature to be 50-56 DEG C, adding a 2-methylcyclohexanol solution, adding N-bromoacetamide in batches within 20-40 min, and continuing a reaction for 60-90 min; and adding nickel chloride powder, controlling a stirring speed to be 110-130 rpm, continuing the reaction for 2-4 h, lowering the temperature to 20-25 DEG C, then carrying out standing for 30-50 min, subjecting the obtained solution to layering, separating an oil layer, washing the oil layer with a potassium bromide solution for 20-40 min, then washing the oil layer with a butyl formate solution for 30-50 min, carrying out recrystallization in a 1-butanol solution, and carrying out dehydration with a dehydrating agent so as to obtain the finished levodopa.
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Paragraph 0017; 0018; 0021; 0022; 0023-0026
(2018/07/30)
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- Tetrabutylammonium Fluoride as a Mild and Versatile Reagent for Cleaving Boroxazolidones to Their Corresponding Free α-Amino Acids
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Protection of α-amino acids with 9-borabicyclo[3.3.1]nonane (9-BBN) to give their corresponding boroxazolidones is highly attractive, as it concurrently masks both the amino and the carboxylic acid functionalities. However, the harsh methods required for deprotection of these boroxazolidones have limited their use. Herein, we report that tetrabutylammonium fluoride serves as a mild and versatile reagent that can be used to cleave boroxazolidones to their corresponding free α-amino acids. The reaction conditions were explored, including the use of various nucleophilic fluoride sources, solvents, and reaction temperatures. Nucleophilic fluoride sources comprising an ammonium cation proved superior to other countercations. The scope of the reaction was extended to the cleavage of B,B-diphenyl- and B,B-diethyl boroxazolidone complexes. Furthermore, a wide range of α-amino acid side-chain functionalities were shown to be compatible, including acids, esters, amides, thiols, thioethers, alkynes, phenols, basic heterocycles, and important biorelevant molecules such as glutathione, (S)-adenosyl-l-homocysteine, and l-biocytin.
- Poulie, Christian B. M.,Bunch, Lennart
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supporting information
p. 1475 - 1478
(2017/04/01)
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- Preparation method of levodopa
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The invention discloses a preparation method of levodopa. The preparation method comprises the following steps: in the absence of a solvent, under the catalytic action of a catalyst A, performing a three-component one-pot asymmetric cyanosilylation reaction on 3,4-dimethoxyphenylacetaldehyde, L-phenylglycinol and TMSCN to obtain a compound (III); hydrolyzing the compound (III) under an acidic condition to obtain a compound (IV); removing chiral auxiliary groups from the compound (IV) through catalytic hydrogenation to obtain the levodopa. By the preparation method, the levodopa is prepared by catalyzing the cyanosilylation reaction by using cheap and environment-friendly Lewis acid magnesium, the stereoselectivity is high, and low temperature, anhydrous and anaerobic conditions and other harsh operating conditions are not required; in addition, low-toxicity and safe trimethylsilyl cyanide is used for substituting a highly toxic reagent sodium cyanide or potassium cyanide, so that the production safety is improved and the environment pollution is reduced; the preparation method has the advantages of a mild reaction condition, simple and convenient operation, high atom utilization rate, environment friendliness, low production cost and the like, and is suitable for industrial popularization and application.
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Paragraph 0023; 0064; 0066; 0068; 0070; 0072; 0074
(2018/03/01)
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- Compositions and methods for producing benzylisoquinoline alkaloids
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The present invention relates to host cells that produce compounds that are characterized as benzylisoquinolines, as well as select precursors and intermediates thereof. The host cells comprise one, two or more heterologous coding sequences wherein each of the heterologous coding sequences encodes an enzyme involved in the metabolic pathway of a benzylisoquinoline, or its precursors or intermediates from a starting compound. The invention also relates to methods of producing the benzylisoquinoline, as well as select precursors and intermediates thereof by culturing the host cells under culture conditions that promote expression of the enzymes that produce the benzylisoquinoline or precursors or intermediates thereof.
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Page/Page column 4
(2016/05/19)
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- Biochemical evidence of L-dopa synthesis in a cytokine-resilient Aspergillus oryzae
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The present work describes the microbiological production of 3,4 dihydroxy-L-phenylalanine (L-dopa) from a cytokine-inhibited mold culture of Aspergillus oryzae (strain Ck-R6). A level of 15 μg/ml cytokine was found optimal for culture resistance and better dopa-dopamine activity. Synthetic L-tyrosine was used as a basal carbon source. The aerobic reactions were carried out using pre-grown mycelia as a direct tyrosinase source. The mycelia were cultivated using 200 ml of GPY mineral-salt medium and developed at 30°C for 48 h (240 rpm) in 500 ml Erlenmeyer flasks. L-dopa production was found optimal when L-ascorbic acid (5 mg/ml) was added 6 min after starting the reaction (120 rpm). The maximal production (2.2 mg/ml L-dopa) was obtained when L-tyrosine concentration was 2.5 mg/ml. Mycelial level (75 mg/ml) and time of reaction (40 min) were also evaluated. L-Tyrosine consumption was found to be 2.1 mg/ml. After optimizing the reaction conditions, particularly L-ascorbic acid addition, a 30% improved L-dopa yield was achieved compared to control when the parameters including time of reaction (40 min), L-tyrosine concentration (2.5 mg/ml) and temperature (50°C) were optimized by two-factorial Plackett-Burman design (PBD).
- Ali, Sikander,Saleem, Rabia
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p. 287 - 293
(2016/08/20)
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- Structure-Activity Relationship Study of Hydroxycoumarins and Mushroom Tyrosinase
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The structure-activity relationships of four hydroxycoumarins, two with the hydroxyl group on the aromatic ring of the molecule and two with the hydroxyl group replacing hydrogen of the pyrone ring, and their interactions with mushroom tyrosinase were studied. These compounds displayed different behaviors upon action of the enzyme. The two compounds, ar-hydroxylated 6-hydroxycoumarin and 7-hydroxycoumarin, were both weak substrates of the enzyme. Interestingly, in both cases, the product of the catalysis was the 6,7-hydroxycoumarin, although 5,6- and 7,8-isomers could also theoretically be formed. Additionally, both were able to reduce the formation of dopachrome when tyrosinase acted on its typical substrate, l-tyrosine. Although none of the compounds that contained a hydroxyl group on the pyrone ring were substrates of tyrosinase, the 3-hydroxycoumarin was a potent inhibitor of the enzyme, and the 4-hydroxycoumarin was not an inhibitor. These results were compared with those obtained by in silico molecular docking predictions to obtain potentially useful information for the synthesis of new coumarin-based inhibitors that resemble the structure of the 3-hydroxycoumarin.
- Asthana, Shailendra,Zucca, Paolo,Vargiu, Attilio V.,Sanjust, Enrico,Ruggerone, Paolo,Rescigno, Antonio
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p. 7236 - 7244
(2015/09/01)
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- A Method for Synthesizing a Catecholamine Using Plasma Polymerization
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The present invention relates to a method for manufacturing a catecholamine-based compound using a plasma polymerization method and, more specifically, to a method for artificially synthesizing a unimolecular compound capable of having various catecholamines, i.e. a hydroxyl group (-OH) as a ortho-group of a benzene ring and various alkylamines as a para-group, from a catecholamine precursor material such as phenol, aniline, etc, using a dry plasma polymerization method.COPYRIGHT KIPO 2015
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Page/Page column 19
(2017/01/02)
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- Chiral ligand-exchange resolution of underivatized amino acids on a dynamically modified stationary phase for RP-HPTLC
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The synthesis of Spi(τ-dec), derived from the selective alkylation of L-spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) at the τ-nitrogen of its heteroaromatic ring, with a linear hydrocarbon chain of 10 carbon atoms, is described here for the first time. Spi(τ-dec) was successfully employed in the past to prepare home-made chiral columns for chiral ligand-exchange high-performance liquid chromatography. In the present article a new method is described, using Spi(τ-dec) as a chiral selector in high-performance thin-layer chromatography (HPTLC): commercial hydrophobic plates were first coated with Spi(τ-dec) and then treated with copper sulfate. The performance of this new chiral stationary phase was tested against racemic mixtures of aromatic amino acids, after appropriate optimization of both the conditions of preparation of the plates and the mobile phase composition. The enantioselectivity values obtained for the studied compounds were higher than those reported in the literature for similar systems. The method employed here for the preparation of chiral HPTLC plates proved practical, efficient, and inexpensive. Chirality 26:313-318, 2014. 2014 Wiley Periodicals, Inc.
- Remelli, Maurizio,Faccini, Stefania,Conato, Chiara
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p. 313 - 318
(2014/06/09)
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- 3,4-Dihydroxy-l-phenylalanine as a biomarker of oxidative damage in proteins: Improved detection using cloud-point extraction and HPLC
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Oxidized protein adducts are formed under conditions of oxidative stress and may represent a valuable biomarker for a variety of diseases which share this common aetiology. A suitable candidate biomarker for oxidized proteins is protein-bound 3,4-dihydrox
- McPherson, Peter A.C.,Türemen, Bryn T.
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p. 376 - 381
(2015/01/09)
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- SEPARATING AGENT FOR CHROMATOGRAPHY
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A separating agent for chromatography is provided that is useful for the separation of specific compounds, e.g., for the optical resolution of amino acids. This separating agent for chromatography provides a higher productivity and contains a crown ether-like cyclic structure and optically active binaphthyl. This separating agent for chromatography containing a crown ether-like cyclic structure and optically active binaphthyl is provided by introducing a substitution group for binding to carrier into a specific commercially available 1,1′-binaphthyl derivative that has substituents at the 2, 2′, 3, and 3′ positions, then introducing a crown ether-like cyclic structure, and subsequently chemically bonding the binaphthyl derivative to the carrier through the substitution group for binding to carrier.
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Paragraph 0074; 0075
(2013/08/15)
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- Unusual isomeric corniculatolides from mangrove, Aegiceras corniculatum
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Four new isomeric macrolides of combretastatin D-2 congeners named isocorniculatolide A (1), 11-O-methylisocorniculatolide A (2), 11-O-methylcorniculatolide A (3), and 12-hydroxy-11-O-methylcorniculatolide A (4), and the known corniculatolide A (5), arjunolic acid, and maslinic acid were isolated from the CHCl3 extract of the bark of Aegiceras corniculatum. The structures of the new compounds (1-4) were elucidated by a combination of spectroscopic analysis (1-5), chemical modifications, and single-crystal X-ray analysis (1).
- Ponnapalli, M. Gowri,Annam, S. Ch. V. A. Rao,Ravirala, Saidulu,Sukki, Sushma,Ankireddy, Madhu,Tuniki, V. Raju
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supporting information; scheme or table
p. 275 - 279
(2012/05/05)
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- Continuous-flow step gradient mass spectrometry based method for the determination of kinetic parameters of immobilized mushroom tyrosinase in equilibrating conditions: Comparison with free enzyme
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A mass spectrometry (MS)-based methodology for enzymatic assay in equilibrium conditions was designed and evaluated. This on-line assay involves the introduction of a continuous-flow step gradient (CFSG) of a substrate solution in the column containing immobilized enzyme and the simultaneous tracking of the product formation. We showed that the constant concentration of substrate in the entire bioreactor for an appropriate duration ensures the equilibration of the studied enzyme (mushroom tyrosinase). Under these conditions, it was demonstrated also that the kinetic and enzymatic parameters (Michaelis-Menten constant, KM, the maximal specific activity, SAmax) are independent of the flow rate of the mobile phase. The feasibility of the mentioned approach for inhibitory tests was also investigated. The coupling of the mass spectrometer to the bio-reactor allows the selective monitoring of the enzymatic reaction products and increases their detection level. Very high sensitivity, 500 pmol/min/column, and selective monitoring of the products of the enzymatic reaction are allowed by MS detection. The methodology developed here constitutes a sensitive analytical tool to study enzymes requiring long equilibration times. Copyright
- Salwinski, Aleksander,Delepee, Raphael,Maunit, Benot
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experimental part
p. 3549 - 3554
(2012/03/27)
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- Phototriggering of neuroactive amino acids from 5,6-benzocoumarinyl conjugates
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Uncaging of several neuroactive amino acids, namely β-alanine, tyrosine, 3,4-dihydroxyphenylalanine (DOPA) and glutamic acid from the corresponding 5,6-benzocoumarinyl conjugates was carried out by irradiation at different wavelengths and in different solvent systems. The release of the various amino acids was faster in ACN/HEPES buffer mixtures and for the tyrosine conjugate, an increase in the photolysis reaction rates and the quantitative uncaging of the amino acid was associated with increasing water content in the solvent mixture.
- Fernandes, Maria José G.,Costa, Susana P.G.,Gonalves, M. Sameiro T.
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p. 2422 - 2426
(2011/05/06)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 61
(2010/12/31)
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- A PROCESS FOR SUBSTITUTION ON AROMATIC RINGS
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A process for preparing a substituted aromatic compound, comprising combining an aromatic compound and cuprous (Cu+) ions in a reaction vessel in an essentially oxygen-free environment, and adding to said reaction vessel a source of an electrophile or a nucleophile substituent, to form an aromatic compound product which is ring-substituted with said electrophile or nucleophile at a position which was originally occupied by hydrogen, and isolating the substituted aromatic compound from the reaction mixture.
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Page/Page column 18-19
(2010/06/17)
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- Synthesis of novel 3,5-diaryl pyrazole derivatives using combinatorial chemistry as inhibitors of tyrosinase as well as potent anticancer, anti-inflammatory agents
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In the present article, we have synthesized a combinatorial library of 3,5-diaryl pyrazole derivatives using 8-(2-(hydroxymethyl)-1-methylpyrrolidin-3- yl)-5,7-dimethoxy-2-phenyl-4H-chromen-4-one (1) and hydrazine hydrate in absolute ethyl alcohol under the refluxed conditions. The structures of the compounds were established by IR, 1H NMR and mass spectral analysis. All the synthesized compounds were evaluated for their anticancer activity against five cell lines (breast cancer cell line, prostate cancer cell line, promyelocytic leukemia cell line, lung cancer cell line, colon cancer cell line) and anti-inflammatory activity against TNF-α and IL-6. Out of 15 compounds screened, 2a and 2d exhibited promising anticancer activity (61-73% at 10 μM concentration) against all selected cell lines and IL-6 inhibition (47% and 42% at 10 μM concentration) as in comparison to standard flavopiridol (72-87% inhibition at 0.5 μM) and dexamethasone (85% inhibition at 1 μM concentration), respectively. Cytotoxicity of the compounds checked using CCK-8 cell lines and found to be nontoxic to slightly toxic. Out of 15, four 3,5-diaryl pyrazole derivatives exhibiting potent inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase. The IC50 values of compounds (2a, 2d, 2h and 2l) for monophenolase inhibition were determined to range between 1.5 and 30 μM. Compounds 2a, 2d, 2h and 2l also inhibited diphenolase significantly with IC50 values of 29.4, 21.5, 2.84 and 19.6 μM, respectively. All four 3,5-diaryl pyrazole derivatives were active as tyrosinase inhibitors (2a, 2d, 2h and 2l), and belonging to competitive inhibitors. Interestingly, they all manifested simple reversible slow-binding inhibition against diphenolase.
- Bandgar, Babasaheb P.,Totre, Jalinder V.,Gawande, Shrikant S.,Khobragade,Warangkar, Suchita C.,Kadam, Prasad D.
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experimental part
p. 6149 - 6155
(2010/09/15)
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- Design of a biosensor based on 1-(4-nitrophenyl)-2,5-di(2-thienyl)-1H pyrrole
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Immobilization of polyphenol oxidase (tyrosinase, E.C. 1.14.18.1) was achieved on a copolymer of 1-(4-nitrophenyl)-2,5-di(2-thienyl)-1H-pyrrole [SNS(NO2)] with pyrrole ([SNS(NO2)]/PPy) via electrochemical polymerization. Two different substrates; catechol and l-tyrosine were used for the characterization of biosensor. The kinetic parameters of the biosensor, maximum reaction rate of the enzyme (Vmax) and Michaelis-Menten constant (Km) were determined for two different substrates. Vmax was found as 0.02 μmol/min electrode for both substrates. Km values were determined as 250 and 2 mM for catechol and l-tyrosine respectively. Calibration curves for enzyme activity versus substrate concentration were plotted between 0.05 and 0.5 M catechol and between 0.8 and 2.5 mM l-tyrosine. Optimum temperature and pH, operational and storage stabilities of immobilized enzyme were examined.
- Tuncagil, Sevinc,Varis, Serhat,Toppare, Levent
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experimental part
p. 195 - 199
(2010/11/05)
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- Design, synthesis, and preliminary pharmacological evaluation of new imidazolinones as l-DOPA prodrugs
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l-DOPA, the immediate biological precursor of dopamine, is still considered the drug of choice in the treatment of Parkinson's disease. However, therapy with l-DOPA is associated with a number of acute problems. With the aim to increase the bioavailability after oral administration, we designed a multi-protected l-DOPA prodrugs able to release the drug by both spontaneous chemical or enzyme catalyzed hydrolysis. The new compounds have been synthesized and preliminarily evaluated for their water solubility, log P, chemical stability, and enzymatic stability. The results indicate that the incorporation of the amino acidic moiety of l-DOPA into an imidazoline-4-one ring provides prodrugs sufficiently stable to potentially cross unchanged the acidic environment of the stomach, and to be absorbed from the intestine. They also might be able to release l-DOPA in human plasma after enzymatic hydrolysis. The ability of prodrugs 6a-b to increase basal levels of striatal DA, and influence brain neurochemistry associated with dopaminergic activity following oral administration, as well as the radical-scavenging activity against DPPH for compounds 6a-b and 15a are also reported.
- Giorgioni, Gianfabio,Claudi, Francesco,Ruggieri, Sabrina,Ricciutelli, Massimo,Palmieri, Giovanni F.,Stefano, Antonio Di,Sozio, Piera,Cerasa, Laura S.,Chiavaroli, Annalisa,Ferrante, Claudio,Orlando, Giustino,Glennon, Richard A.
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experimental part
p. 1834 - 1843
(2010/05/02)
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- Floating pharmaceutical composition comprising an active phase and a non-active phase
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The invention concerns a floating pharmaceutical composition consisting of at least a first phase comprising at least a high dose active principle combined with one or several carriers and at least a second phase comprising at least a gas-generating system. The invention also concerns tablets comprising such a pharmaceutical composition and a method for preparing such tablets.
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- A novel and efficient synthesis of DOPA and DOPA peptides by oxidation of tyrosine residues with IBX
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An efficient route to 3,4-dihydroxylphenylalanine (DOPA) and DOPA peptides was described by oxidation of L-tyrosine and L-tyrosine derivatives with 2-iodoxybenzoic acid (IBX). DOPA was obtained after an situ reduction of the corresponding ortho-quinone with sodium dithionite. Oxidation reactions proceeded in good yields and high chemo- and regio-selectivity. The chirality of the DOPA residue was retained under the reaction conditions. The efficiency and the selectivity of the reaction were successfully tested using recyclable polymer-supported IBX.
- Bernini, Roberta,Barontini, Maurizio,Crisante, Fernanda,Ginnasi, Maria Cristina,Saladino, Raffaele
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body text
p. 6519 - 6521
(2011/02/23)
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- Tyrosinase inhibitory polyphenols from roots of Morus Ihou
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Twelve polyphenols (1-12) possessing tyrosinase inhibitory properties were isolated from the methanol (95%) extract of Morus Ihou. The isolated compounds consisted of four flavanones (1 -4), four flavones (5-8), and four phenylbenzofuranes (9-12). Moracin derivative 12 proved to be new a compound which was fully characterized. Compounds 1-12 were evaluated for both monophenolase and diphenolase (the two steps catalyzed by tyrosinase) inhibition to identify the structural characteristics required for mushroom tyrosinase inhibition. We observed that all parent compounds (1, 5, and 9) possessing an unsubstituted resorcinol group were highly effective inhibitors of monophenolase activity (IC50 values of 1.3, 1.2, and 7.4 μM). The potency of the inhibitors diminished with alkyl substitution on either the aromatic ring or the hydroxyl functions. Interestingly, flavone 5 was shown to possess only monophenolase inhibitory activity, but flavanone 1 and phenylbenzofuran 9 inhibited diphenolase as well as monophenolase significantly. The inhibitory mode of these species was also dependent upon the skeleton: phenylbenzofuran 9 manifested a simple competitive inhibition mode for monophenolase and diphenolase; on the other hand flavanone 1 (monophenolase, K3 = 0.1966 min-1 μM-1 k4= 0.0082 min ～1, and Kiapp = 0.0468 μM; diphenolase, k3 = 0.0014 min-1 μM-1 k4 = 0.0013 min-1, and Kiapp = 0.8996 μM) and flavone 5 both showed time-dependent inhibition against monophenolase. Compound 1 operated according to the simple reversible slow binding model whereas compound 5 operated under the enzyme isomerization model.
- Jeong, Seong Hun,Ryu, Young Bae,Curtis-Long, Marcus J.,Ryu, Hyung Won,Baek, Yoon Su,Kang, Jae Eun,Lee, Woo Song,Park, Ki Hun
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experimental part
p. 1195 - 1203
(2010/06/14)
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- Convenient synthesis of acetonide-protected 3,4-dihydroxyphenylalanine (DOPA) for Fmoc solid-phase peptide synthesis
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We report a facile approach to the synthesis of acetonide and Fmoc-protected 3,4-dihydroxyphenylalanine (DOPA), Fmoc-DOPA(acetonide)-OH. By protecting the amino group of DOPA with a phthaloyl group and the carboxyl group as a methyl ester, acetonide protection of the catechol of DOPA derivative was realized in the presence of p-toluenesulfonic acid. Following removal of protecting groups, the intermediate was converted to Fmoc-DOPA(acetonide)-OH, which was successfully incorporated into a short DOPA-containing peptide, derived from marine tubeworm cement proteins Pc1 and Pc2.
- Liu, Zhongqiang,Hu, Bi-Huang,Messersmith, Phillip B.
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p. 5519 - 5521
(2008/12/22)
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- Stereospecificity of mushroom tyrosinase immobilized on a chiral and a nonchiral support
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Mushroom tyrosinase was immobilized from an extract onto glass beads covered with the cross-linked totally cinnamoylated derivates of D-sorbitol (sorbitol cinnamate) and glycerine (glycerine cinnamate). The enzyme was immobilized onto the support by direct adsorption, and the quantity of immobilized tyrosinase was higher for sorbitol cinnamate, the support with the higher number of esterified hydroxyls per unit of monosacharide, than for glycerine cinnamate. The results obtained from the stereospecificity study of the monophenolase and diphenolase activity of immobilized mushroom tyrosinase are reported. The enantiomers L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, DL-α-methyldopa, L-isoprenaline, DL-isoprenaline, L-adrenaline, DL-adrenaline, L-noradrenaline, and D-noradrenaline were assayed with tyrosinase immobilized on a chiral support (sorbitol cinnamate), whereas L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, and DL-α-methyldopa were assayed with tyrosinase immobilized on a nonchiral support (glycerine cinnamate). The same Vmaxapp values for each series of enantiomers were obtained. However, the Kmapp values were different, the L isomers showing lower values than the DL isomers, whereas the highest K mapp value was obtained with D isomers. No difference was observed in the stereospecificity of tyrosinase immobilized on a chiral (sorbitol cinnamate) or nonchiral (glycerine cinnamate) support.
- Marin-Zamora, Maria Elisa,Rojas-Melgarejo, Francisco,Garcia-Canovas, Francisco,Garcia-Ruiz, Pedro Antonio
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p. 4569 - 4575
(2008/02/09)
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- Discovery of a novel nonphosphorylated pentapeptide motif displaying high affinity for Grb2-SH2 domain by the utilization of 3′-substituted tyrosine derivatives
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The growth factor receptor-bound protein 2 (Grb2) is an SH2 domain-containing docking module that represents an attractive target for anticancer therapeutic intervention. An impressive number of synthetic Grb2-SH2 domain inhibitors have been identified; however, clinical agents operating by this mechanism are lacking, due in part to the unique requirement of anionic phosphate-mimicking functionality for high SH2 domain-binding affinity or the extended peptide nature of most inhibitors. In the current study, a new binding motif was successfully developed by the incorporation of 3′-substituted tyrosine derivatives into a simplified nonphosphorylated cyclic pentapeptide scaffold (4), which resulted in high affinity Grb2-SH2 inhibitors without any phosphotyrosine or phosphotyrosine mimetics. The new L-amino acid analogues bearing an additional nitro, amino, hydroxy, methoxy or carboxy group at the 3′-position of the phenol ring of tyrosine were prepared in an orthogonally protected form suitable for solid-phase peptide synthesis using Fmoc protocols. The incorporation of these residues into cyclic peptides composed of a five-amino acid sequence motif, Xx′-Leu-(3′- substituted-Tyr)-Ac6c-Asn, provided a brand new class of nonphosphorylated Grb2 SH2 domain inhibitors with reduced size, charge and peptidic character. The highest binding affinity was exhibited by the 3′-aminotyrosine (3′-NH2-Tyr)-containing (R)-sulfoxide-cyclized pentapeptide (10b) with an IC50 = 58 nM, the first example with low-nanomolar affinity for a five-amino acid long sequence binding to Grb2-SH2 domain free of any phosphotyrosine or phosphotyrosine mimics. However, the incorporation of 3′-NO2-Tyr, 3′-OH-Tyr or 3′-OCH3-Tyr surrogates in the pentapeptide scaffold is detrimental to Grb2-SH2 binding. These observations were rationalized using molecular modeling. More significantly, the best Grb2-SH2 inhibitor 10b showed excellent activity in inhibiting the growth of erbB2-dependent MDA-MB-453 tumor cell lines with an IC50 value of 19 nM. This study is the first attempt to identify novel nonphosphorylated high affinity Grb2 SH2 inhibitors by the utilization of 3′-substituted tyrosine derivatives, providing a promising new strategy and template for the development of non-pTyr-containing Grb2-SH2 domain antagonists with potent cellular activity, which potentially may find value in chemical therapeutics for erbB2-related cancers.
- Song, Yan-Li,Peach, Megan L.,Roller, Peter P.,Qiu, Su,Wang, Shaomeng,Long, Ya-Qiu
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p. 1585 - 1596
(2007/10/03)
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- Probing biocatalytic transformations with CdSe-ZnS QDs
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CdSe/ZnS QDs enable the optical probing of the biocatalytic oxidation of tyrosine derivatives and of the scission of peptides by thrombin. CdSe/ZnS QDs were modified with tyrosine methyl ester or with a tyrosine-containing peptide. The tyrosine units were reacted with tyrosinase/O2 to yield the respective l-DOPA and quinone derivatives. The luminescence of QDs modified by the enzyme-generated quinone units is quenched. The quinone-functionalized peptide associated with the QDs was cleaved by thrombin, a process that restored the luminescence of the QDs. Copyright
- Gill, Ron,Freeman, Ronit,Xu, Jian-Ping,Willner, Itamar,Winograd, Shira,Shweky, Itzik,Banin, Uri
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p. 15376 - 15377
(2007/10/03)
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- Cavity effects on the enantioselectivity of chiral amido[4]resorcinarene stereoisomers
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The dramatic effects of the size and hydrophilic/hydrophobic properties of cavities on the intrinsic reaction kinetics and dynamics is shown by the gas-phase reaction of (R)-(-)-2-butylamine and complexes of stereoisomeric amido[4]resorcinarene hosts with aromatic amino acids. The graph shows the kinetic plots of the base-induced loss of L-Phe (green), L-Tyr (red), and L-dopa (blue).
- Botta, Bruno,Subissati, Deborah,Tafi, Andrea,Delle Monache, Giuliano,Filippi, Antonello,Speranza, Maurizio
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p. 4767 - 4770
(2007/10/03)
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- Synthesis and crosslinking of catechol containing copolypeptides
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The synthesis of moisture-resistant adhesive polypeptides, conditions for their use, and conditions for controlling characteristics of the crosslinked matrix are disclosed. By specifically manipulating the conditions under which these networks are formed, the characteristics of the networks may be precisely regulated. These manipulatable adhesive networks are water-based, show exceptional bonding capabilities toward wet materials (including biological tissues), and have a variety of biotechnological applications.
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