156-06-9Relevant articles and documents
Danishefsky,Hirama
, p. 4565,4566 (1977)
Continuous Colorimetric Assay That Enables High-Throughput Screening of N -Acetylamino Acid Racemases
Sánchez-Carrón, Guiomar,Fleming, Toni,Holt-Tiffin, Karen E.,Campopiano, Dominic J.
, p. 3923 - 3928 (2015)
N-Acetyl amino acid racemases (NAAARs) have demonstrated their potential in the enzymatic synthesis of chiral amino acids, molecules of significant biotechnology interest. In order to identify novel activities and to improve these enzymes by engineering approaches, suitable screening methods are necessary. Previous engineering of the NAAAR from Amycolatopsis Ts-1-60 was achieved by relying on an in vivo selection system that linked the viability of an E. coli l-methionine auxotroph to the activity of the improved enzyme. However, this assay was only suitable for the screening of N-acetyl-d-methionine, therefore limiting the potential to evolve this enzyme toward other natural or non-natural acetylated amino acids. Here, we report the optimization and application of a spectrophotometric microtiter-plate-based assay for NAAAR. The assay is based on the detection of the amino acid reaction product formed by hydrolysis of the N-acylated substrate by an l-amino acid acylase and its subsequent oxidation by an FAD-dependent l-amino acid oxidase (l-AAO). Cofactor recycling of the l-AAO leads to the formation of hydrogen peroxide which is easily monitored using horseradish peroxidase (HRP) and o-dianisidine. This method allowed for the determination of the kinetic parameters of NAAAR and led to the identification of N-acetyl-d-naphthylalanine as a novel NAAAR substrate. This robust method is also suitable for the high-throughput screening of NAAAR mutant gene libraries directly from cell lysates. (Chemical Equation Presented)
E Erlenmeyer
, p. 3002 (1900)
Characterization of aromatic aminotransferases from Ephedra sinica Stapf
Kilpatrick, Korey,Pajak, Agnieszka,Hagel, Jillian M.,Sumarah, Mark W.,Lewinsohn, Efraim,Facchini, Peter J.,Marsolais, Frédéric
, p. 1209 - 1220 (2016)
Ephedra sinica Stapf (Ephedraceae) is a broom-like shrub cultivated in arid regions of China, Korea and Japan. This plant accumulates large amounts of the ephedrine alkaloids in its aerial tissues. These analogs of amphetamine mimic the actions of adrenaline and stimulate the sympathetic nervous system. While much is known about their pharmacological properties, the mechanisms by which they are synthesized remain largely unknown. A functional genomics platform was established to investigate their biosynthesis. Candidate enzymes were obtained from an expressed sequence tag collection based on similarity to characterized enzymes with similar functions. Two aromatic aminotransferases, EsAroAT1 and EsAroAT2, were characterized. The results of quantitative reverse transcription-polymerase chain reaction indicated that both genes are expressed in young stem tissue, where ephedrine alkaloids are synthesized, and in mature stem tissue. Nickel affinity-purified recombinant EsAroAT1 exhibited higher catalytic activity and was more homogeneous than EsAroAT2 as determined by size-exclusion chromatography. EsAroAT1 was highly active as a tyrosine aminotransferase with α-ketoglutarate followed by α-ketomethylthiobutyrate and very low activity with phenylpyruvate. In the reverse direction, catalytic efficiency was similar for the formation of all three aromatic amino acids using l-glutamate. Neither enzyme accepted putative intermediates in the ephedrine alkaloid biosynthetic pathway, S-phenylacetylcarbinol or 1-phenylpropane-1,2-dione, as substrates.
Transamination Reaction of Hydrophobic Pyridoxal with an α-Amino Acid in Functionalized Bilayer Vesicles: Co-operative Catalysis by the Imidazolyl Group and Copper(II) Ions
Murakami, Yukito,Kikuchi, Jun-ichi,Imori, Toru,Akiyoshi, Kazunari
, p. 1434 - 1436 (1984)
1-(N,N-Dihexadecylcarbamoylmethyl)-2-methyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride (PL+2C16) undergoes a transamination reaction with L-phenylalanine in single-walled bilayer vesicles formed from two different peptide lipids (N+C5Ala2C16 and N+C5His2C16); co-ordination of copper(II) ion to the Schiff-base intermediate results in a marked rate acceleration.
Recombinant expression and characterization of a l-amino acid oxidase from the fungus Rhizoctonia solani
Hahn, Katharina,Neumeister, Katrin,Mix, Andreas,Kottke, Tilman,Gr?ger, Harald,Fischer von Mollard, Gabriele
, p. 2853 - 2864 (2017)
l-Amino acid oxidases (L-AAOs) catalyze the oxidative deamination of l-amino acids to the corresponding α-keto acids, ammonia, and hydrogen peroxide. l-AAOs are homodimeric enzymes with FAD as a non-covalently bound cofactor. They are of potential interest for biotechnological applications. However, heterologous expression has not succeeded in producing large quantities of active recombinant l-AAOs with a broad substrate spectrum so far. Here, we report the heterologous expression of an active l-AAO from the fungus Rhizoctonia solani in Escherichia coli as a fusion protein with maltose-binding protein (MBP) as a solubility tag. After purification, it was possible to remove the MBP-tag proteolytically without influencing the enzyme activity. MBP-rsLAAO1 and 9His-rsLAAO1 converted basic and large hydrophobic l-amino acids as well as methyl esters of these l-amino acids. The progress of the conversion of l-phenylalanine and l-leucine into the corresponding α-keto acids was determined by HPLC and 1H-NMR analysis of reaction mixtures, respectively. Enzymatic activity was stimulated 50–100-fold by SDS treatment. Km values ranging from 0.9–10?mM and vmax values from 3 to 10?U?mg?1 were determined after SDS activation of 9His-rsLAAO1 for the best substrates. The enzyme displayed a broad pH optimum between pH 7.0 and 9.5. In summary, a successful overexpression of recombinant l-AAO in E. coli was established that results in a promising enzymatic activity and a broad substrate spectrum for biotechnological application.
Expression, characterization, and site-specific covalent immobilization of an L-amino acid oxidase from the fungus Hebeloma cylindrosporum
Bloess, Svenja,Beuel, Tobias,Krüger, Tobias,Sewald, Norbert,Dierks, Thomas,Fischer von Mollard, Gabriele
, p. 2229 - 2241 (2019)
l-Amino acid oxidases (LAAOs) are flavoproteins, which use oxygen to deaminate l-amino acids and produce the corresponding α-keto acids, ammonia, and hydrogen peroxide. Here we describe the heterologous expression of LAAO4 from the fungus Hebeloma cylindrosporum without signal sequence as fusion protein with a 6His tag in Escherichia coli and its purification. 6His-hcLAAO4 could be activated by exposure to acidic pH, the detergent sodium dodecyl sulfate, or freezing. The enzyme converted 14 proteinogenic l-amino acids with l-glutamine, l-leucine, l-methionine, l-phenylalanine, l-tyrosine, and l-lysine being the best substrates. Methyl esters of these l-amino acids were also accepted. Even ethyl esters were converted but with lower activity. Km values were below 1?mM and vmax values between 19 and 39?U?mg?1 for the best substrates with the acid-activated enzyme. The information for an N-terminal aldehyde tag was added to the coding sequence. Co-expressed formylglycine-generating enzyme was used to convert a cysteine residue in the aldehyde tag to a Cα-formylglycine residue. The aldehyde tag did not change the properties of the enzyme. Purified Ald-6His-hcLAAO4 was covalently bound to a hexylamine resin via the Cα-formylglycine residue. The immobilized enzyme could be reused repeatedly to generate phenylpyruvate from l-phenylalanine with a total turnover number of 17,600 and was stable for over 40?days at 25?°C.
Studies on the L-2-hydroxy-acid oxidase 2 catalyzed metabolism of S-mandelic acid and its analogues
Zhang, Yang,Su, Chen,Lei, Jinxiu,Chen, Lu,Hu, Haihong,Zeng, Su,Yu, Lushan
, p. 187 - 193 (2019)
Mandelic acid (MA) is generally used as a biomarker of the exposure of styrene, which is classified as a class of hazardous environmental pollutants, and also used as an important chiral intermediate in pharmaceutical industry. The previous studies have found the excretion of phenylglyoxylic acid (PGA) in human and rat, a metabolite of MA, was mainly from S-MA rather than R-MA. The metabolic mechanism, however, is not clear. In order to explore the possible metabolic mechanism, the enzyme types involved in the stereoselectivity metabolism of MA were firstly studied, and then human and rat long-chain 2-hydroxy-acid oxidase 2 (HAO2) were recombinantly expressed to study the metabolic profiles of S-MA and its analogues. The results indicated that HAO2 might catalyze the stereoselectivity metabolism of S-MA in rats. Human HAO2 (hHAO2) and rat HAO2 (rHAO2) isozymes β1 and β2 were successfully cloned and expressed with high purity and good enzyme activities. The enzyme kinetic profiles of these enzymes were different for S-MA and analogues. The order of catalytic efficiency for hHAO2 and rHAO2, however, was reverse. It might be relevance to the difference in active amino acid residues and loop 4 in human and rat L-2-hydroxy acid oxidase isozyme B crystal structures.
2H-thiazolo [3, 2-b]-1, 2, 4-triazine-3, 7-diketone derivative and application thereof
-
, (2020/12/29)
The invention discloses a 2Hthiazolo [3, 2b] 1, 2, 4triazine 3, 7diketone derivative as shown in a general formula I or pharmaceutically acceptable hydrate and salt thereof, the 2Hthiazolo [3, 2b] 1,2, 4triazine 3, 7diketone derivative comprises stereoisomers or tautomers thereof, and R1 and R2 in the general formula I can be optionally selected from one, two or three independently selected fromhydrogen, alkyl, alkoxy, halogen, hydroxyl, acetyl, propionyl, nitro or trifluoromethyl. The 1, 2, 4-triazine 3, 7diketone derivative has an obvious inhibiting effect on acetylcholin esterase, and isused for enhancing the memory of a patient suffering from dementia and Alzheimer's disease. The invention also relates to a preparation method of the compound and the application of the compound in preparation of drugs for treating Alzheimer's disease.
Exploration of Transaminase Diversity for the Oxidative Conversion of Natural Amino Acids into 2-Ketoacids and High-Value Chemicals
Chen, Yanchun,Cui, Xuexian,Cui, Yinglu,Li, Chuijian,Li, Ruifeng,Li, Tao,Sun, Jinyuan,Wu, Bian,Zhu, Tong
, p. 7950 - 7957 (2020/08/21)
The use of 2-ketoacids is very common in feeds, food additives, and pharmaceuticals, and 2-ketoacids are valuable precursors for a plethora of chemically diverse compounds. Biocatalytic synthesis of 2-ketoacids starting from l-amino acids would be highly desirable because the substrates are readily available from biomass feedstock. Here, we report bioinformatic exploration of a series of aminotransferases (ATs) to achieve the desired conversion. Thermodynamic control was achieved by coupling an l-glutamate oxidation reaction in the cascade for the recycling of the amine acceptor. These enzymes were able to convert a majority of proteinogenic amino acids into the corresponding 2-ketoacids with high conversion (up to 99percent) and atom-efficiency. Furthermore, this enzyme cascade was extendable, and one-pot two-step processes were established for the synthesis of d-amino acids and N-methylated amino acids, achieving great overall conversion (up to 99percent) and high ee values (>99percent). These developed enzymatic methodologies offer convenient routes for utilizing amino acids as synthetic reagents.
