- Dissecting structural and electronic effects in inducible nitric oxide synthase
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Nitric oxide synthases (NOSs) are haem-thiolate enzymes that catalyse the conversion of L-arginine (L-Arg) into NO and citrulline. Inducible NOS (iNOS) is responsible for delivery of NO in response to stressors during inflammation. The catalytic performance of iNOS is proposed to rely mainly on the haem midpoint potential and the ability of the substrate L-Arg to provide a hydrogen bond for oxygen activation (O-O scission). We present a study of native iNOS compared with iNOS-mesohaem, and investigate the formation of a low-spin ferric haem-aquo or -hydroxo species (P) in iNOS mutant W188H substituted with mesohaem. iNOS-mesohaem and W188H-mesohaem were stable and dimeric, and presented substrate-binding affinities comparable to those of their native counterparts. Single turnover reactions catalysed by iNOSoxy with L-Arg (first reaction step) or N-hydroxy-L-arginine (second reaction step) showed that mesohaem substitution triggered higher rates of FeIIO2 conversion and altered other key kinetic parameters. We elucidated the first crystal structure of a NOS substituted with mesohaem and found essentially identical features compared with the structure of iNOS carrying native haem. This facilitated the dissection of structural and electronic effects. Mesohaem substitution substantially reduced the build-up of species P in W188H iNOS during catalysis, thus increasing its proficiency towards NO synthesis. The marked structural similarities of iNOSoxy containing native haem or mesohaem indicate that the kinetic behaviour observed in mesohaem-substituted iNOS is most heavily influenced by electronic effects rather than structural alterations.
- Hannibal, Luciana,Page, Richard C.,Haque, Mohammad Mahfuzul,Bolisetty, Karthik,Yu, Zhihao,Misra, Saurav,Stuehr, Dennis J.
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- Mesohaem substitution reveals how haem electronic properties can influence the kinetic and catalytic parameters of neuronal NO synthase
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NOSs (NO synthases, EC 1.14.13.39) are haem-thiolate enzymes that catalyse a two-step oxidation of L-arginine to generate NO. The structural and electronic features that regulate their NO synthesis activity are incompletely understood. To investigate how haem electronics govern the catalytic properties of NOS, we utilized a bacterial haem transporter protein to overexpress a mesohaem-containing nNOS (neuronal NOS) and characterized the enzyme using a variety of techniques. Mesohaem-nNOS catalysed NO synthesis and retained a coupled NADPH consumption much like the wild-type enzyme. However, mesohaem-nNOS had a decreased rate of Fe(III) haem reduction and had increased rates for haem-dioxy transformation, Fe(III) haem-NO dissociation and Fe(II) haem-NO reaction with O2. These changes are largely related to the 48 mV decrease in haem midpoint potential that we measured for the bound mesohaem cofactor. Mesohaem nNOS displayed a significantly lower Vmax and KmO2 value for its NO synthesis activity compared with wild-type nNOS. Computer simulation showed that these altered catalytic behaviours of mesohaem-nNOS are consistent with the changes in the kinetic parameters. Taken together, the results of the present study reveal that several key kinetic parameters are sensitive to changes in haem electronics in nNOS, and show how these changes combine to alter its catalytic behaviour. The Authors Journal compilation
- Tejero, Jesus,Biswas, Ashis,Haque, Mohammad Mahfuzul,Wang, Zhi-Qiang,Hemann, Craig,Varnado, Cornelius L.,Novince, Zachary,Hille, Russ,Goodwin, Douglas C.,Stuehr, Dennis J.
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- Neuronal nitric oxide synthase isoforms α and μ are closely related calpain-sensitive proteins
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The neuronal nitric oxide synthase isoform nNOSμ, which is expressed in striated muscle, differs from nNOSα, the major brain isoform, by the insertion of 34 amino acid residues between the calmodulin- and flavin- binding domains [J Biol Chem 271:11204-11208 (1996)]. We show here that recombinant, purified nNOSμ, despite the peptide insertion, has the same spectroscopic properties, L-arginine k(cat) and K(m) values, optimal pH, and calmodulin binding affinity constant as nNOSα. However, nNOSμ consumes NADPH and reduces cytochrome c at approximately half the rate of nNOSα. The rates of degradation of the two proteins by rat brain and muscle homogenates show that nNOSμ is degraded more slowly than nNOSα. The in vitro half- lives of nNOSα and nNOSμ are 12 and 50 min, respectively, and calpain is important for this degradation. These short in vitro half-lives suggest that the nNOS isoforms are susceptible to rapid degradation in vivo. The elevated (20-fold) levels of calpain in diseased muscle tissue in Duchenne muscular dystrophy, and the hydrolytic sensitivity of both nNOSμ and nNOSα to this enzyme, may contribute to the deficiency of nNOS activity in the diseased tissue.
- Laine, Romuald,Ortiz De Montellano, Paul R.
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- Arginine Deiminase Uses an Active-Site Cysteine in Nucleophilic Catalysis of L-Arginine Hydrolysis
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Arginine deiminase (EC 3.5.3.6) catalyzes the hydrolysis of l-arginine to citrulline and ammonium ion, which is the first step of the microbial l-arginine degradation pathway. The deiminase conserves the active-site Cys-His-Asp motif found in several related enzymes that catalyze group-transfer reactions from the guanidinium center of arginine-containing substrates. For each of these enzymes, nucleophilic catalysis by the conserved Cys has been postulated but never tested. In this communication we report the results from rapid quench studies of single-turnover reactions carried out with recombinant Pseudomonas aeruginosa arginine deiminase and limiting [14C-1]l-arginine. The citrulline-formation and arginine-decay curves measured at 25 °C were fitted to yield apparent rate constants k = 3.6 ± 0.1 s-1 and k = 4.2 ± 0.1 s-1, respectively. The time course for the formation (k =13 s-1) and decay (k = 6.5 s-1) of 14C-labeled enzyme defined a kinetically competent intermediate. Under the same reaction conditions, the Cys406Ser mutant failed to form the 14C-labeled enzyme intermediate. These results, along with the recently reported enzyme X-ray structure (Galkin, A.; Kulakova, L.; Sarikaya, E.; Lim, K.; Howard, A.; Herzberg, O. J. Biol. Chem. 2004, 279, 14001-14008, evidence a reaction pathway in which l-arginine deimination proceeds via a covalent enzyme intermediate formed by ammonia displacement from the arginine guanidinum carbon by the active-site Cys406. Copyright
- Lu, Xuefeng,Galkin, Andrey,Herzberg, Osnat,Dunaway-Mariano, Debra
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- Directed evolution of an antitumor drug (Arginine Deiminase PpADI) for Increased Activity at Physiological pH
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Arginine deiminase (ADI; EC 3.5.3.6) has been studied as a potential antitumor drug for the treatment of arginine-auxotrophic tumors, such as hepatocellular carcinomas (HCCs) and melanomas. Studies with human lymphatic leukemia cell lines confirmed that ADI is an antiangiogenic agent for treating leukemia. The main limitation of ADI from Pseudomonas plecoglossicida (PpADI) lies in its pH-dependent activity profile, its pH optimum is at 6.5. A pH shift from 6.5 to 7.5 results in an approximately 80% drop in activity. (The pH of human plasma is 7.35 to 7.45.) In order to shift the PpADI pH optimum, a directed-evolution protocol based on an adapted citrulline-screening protocol in microtiter-plate format was developed and validated. A proof of concept for ADI engineering resulted in a pH optimum of pH 7.0 and increased resistance under physiological and slightly alkaline conditions. At pH 7.4, variant M2 (K5T/ D44E/H404R) is four times faster than the wild-type PpADI and retains -50% of its activity relative to its pH optimum, compared to -10% in the case of the wild-type PpADI.
- Zhu, Leilei,Tee, Kang Lan,Roccatano, Danilo,Sonmez, Burcu,Ni, Ye,Sun, Zhi-Hao,Schwaneberg, Ulrich
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- L337H mutant of rat neuronal nitric oxide synthase resembles human neuronal nitric oxide synthase toward inhibitors
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A common dichotomy exists in inhibitor design: should the compounds be designed to block the enzymes of animals in the preclinical studies or to inhibit the human enzyme? We report that a single mutation of Leu-337 in rat neuronal nitric oxide synthase (nNOS) to His makes the enzyme resemble human nNOS more than rat nNOS. We expect that the approach used in this study can unite the dichotomy and speed up the process of inhibitor design and development.
- Fang, Jianguo,Ji, Haitao,Lawton, Graham R.,Xue, Fengtian,Roman, Linda J.,Silverman, Richard B.
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- Mechanisms of catalysis and inhibition operative in the arginine deiminase from the human pathogen Giardia lamblia
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Giardia lamblia arginine deiminase (GlAD), the topic of this paper, belongs to the hydrolase branch of the guanidine-modifying enzyme superfamily, whose members employ Cys-mediated nucleophilic catalysis to promote deimination of l-arginine and its naturally occurring derivatives. G. lamblia is the causative agent in the human disease giardiasis. The results of RNAi/antisense RNA gene-silencing studies reported herein indicate that GlAD is essential for G. lamblia trophozoite survival and thus, a potential target for the development of therapeutic agents for the treatment of giardiasis. The homodimeric recombinant protein was prepared in Escherichia coli for in-depth biochemical characterization. The 2-domain GlAD monomer consists of a N-terminal domain that shares an active site structure (depicted by an in silico model) and kinetic properties (determined by steady-state and transient state kinetic analysis) with its bacterial AD counterparts, and a C-terminal domain of unknown fold and function. GlAD was found to be active over a wide pH range and to accept l-arginine, l-arginine ethyl ester, Nα-benzoyl-l-arginine, and Nω-amino-l-arginine as substrates but not agmatine, l-homoarginine, Nα-benzoyl-l-arginine ethyl ester or a variety of arginine-containing peptides. The intermediacy of a Cys424-alkylthiouronium ion covalent enzyme adduct was demonstrated and the rate constants for formation (k1 = 80 s-1) and hydrolysis (k2 = 35 s-1) of the intermediate were determined. The comparatively lower value of the steady-state rate constant (kcat = 2.6 s-1), suggests that a step following citrulline formation is rate-limiting. Inhibition of GlAD using Cys directed agents was briefly explored. S-Nitroso-l-homocysteine was shown to be an active site directed, irreversible inhibitor whereas Nω-cyano-l-arginine did not inhibit GlAD but instead proved to be an active site directed, irreversible inhibitor of the Bacillus cereus AD.
- Li, Zhimin,Kulakova, Liudmila,Li, Ling,Galkin, Andrey,Zhao, Zhiming,Nash, Theodore E.,Mariano, Patrick S.,Herzberg, Osnat,Dunaway-Mariano, Debra
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- Ruthenium(III) readily abstracts NO from L-arginine, the physiological precursor to NO, in the presence of H2O2. A remarkably simple model system for NO synthases.
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Reaction of [Ru(Hedta)Cl]- with H2O2 in the presence of arginine, produces NO, in the form of an Ru(II)-(NO+) complex and citrulline which is a remarkably simple model system for the physiological NO synthase reaction.
- Marmion,Murphy,Nolan
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- IMPROVED METHOD OF SYNTHESIS AND PURIFICATION OF CITRULLINE
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This invention provides for synthesis of citrulline from a transition metal complex of ornithine using cyanate to derivatize the terminal amino group of ornithine. The invention also provides improved methods for purification of citrulline produced by reaction of cyanate with ornithine via the steps of reprecipitation of copper complex of citrulline, removal of the complexing metal by sulfide precipitation, activated carbon adsorption and antisolvent crystallization.
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Paragraph 00033-00034; 00037-00038
(2020/12/29)
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- l-Arginine and nitric oxide synthesis in the cells with inducible NO synthase
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The effect of citrulline and ammonium chloride on the nitric oxide formation by peritoneal macrophages and liver tissue cells was studied using ESR spectroscopy. In ex vivo models, the incubation of cells capable of expressing inducible NO synthase (iNOS) with interferon-γ resulted in a moderate increase in the amount of hemoglobin–nitric oxide nitrosyl complexes (Heme–NO NCs), whereas incubation with l-citrulline and ammonium chloride increased the amount of Heme–NO NCs by an order of magnitude. It was assumed that a separate cycle of L-arginine and nitric oxide synthesis exists in the peritoneal macrophages and liver cells, with the major participants of the cycle being the inducible NO synthase enzyme (iNOS) and enzymes that synthesize L-arginine from L-citrulline and a nitrogen source. Functioning of this cycle makes immunocompetent cells with iNOS able to produce NO for a long time and in large amounts.
- Kuropteva,Baider,Nagler,Bogatyrenko,Belaia
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p. 174 - 180
(2019/04/25)
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- Enzyme-immobilized metal-organic framework nanosheets as tandem catalysts for the generation of nitric oxide
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An enzyme-immobilized metal-organic framework (MOF) nanosheet system was developed as a tandem catalyst, which converted glucose into gluconic acid and H2O2, and sequentially the latter could be used to catalyze the oxidation of l-arginine to generate nitric oxide in the presence of porphyrinic MOFs as artificial enzymes under physiological pH, showing great potential in cancer depleting glucose for starving-like/gas therapy.
- Gao, Feng,Lei, Jianping,Ling, Pinghua,Qian, Caihua
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supporting information
p. 11176 - 11179
(2020/04/23)
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- Method for preparing L-citrulline crude product and L-citrulline prepared through method
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The invention discloses a method for preparing an L-citrulline crude product and L-citrulline prepared through the method. The method for preparing the L-citrulline crude product includes the steps of preparing L-citrulline liquid, preparing the L-citrulline crude product from the L-citrulline liquid, refining the crude product, and obtaining an L-citrulline finished product. When the method is used for producing the L-citrulline crude product, no ethyl alcohol is used, so the method has the advantages that production conditions are mild, concentration time is short, product purity is high, yield is high and production cost is low.
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Paragraph 0033-0108
(2017/05/05)
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- Engineering nitric oxide synthase chimeras to function as NO dioxygenases
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Nitric oxide synthases (NOSs) catalyze a two-step oxidation of l-arginine to form nitric oxide (NO) and l-citrulline. NOS contains a N-terminal oxygenase domain (NOSoxy) that is the site of NO synthesis, and a C-terminal reductase domain (NOSred) that binds nicotinamide adenine dinucleotide phosphate (NADPH), flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN) and provides electrons to the NOSoxy heme during catalysis. The three NOS isoforms in mammals inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) share high structural similarity but differ in NO release rates and catalytic properties due to differences in enzyme kinetic parameters. These parameters must be balanced for NOS enzymes to release NO, rather than consume it in a competing, inherent NO dioxygenase reaction. To improve understanding, we drew on a global catalytic model and previous findings to design three NOS chimeras that may predominantly function as NO dioxygenases: iNOSoxy/nNOSred (Wild type (WT) chimera), V346I iNOSoxy/nNOSred (V346I chimera) and iNOSoxy/S1412D nNOSred (S1412D chimera). The WT and S1412D chimeras had higher NO release than the parent iNOS, while the V346I chimera exhibited much lower NO release, consistent with expectations. Measurements indicated that a greater NO dioxygenase activity was achieved, particularly in the V346I chimera, which dioxygenated an estimated two to four NO per NO that it released, while the other chimeras had nearly equivalent NO dioxygenase and NO release activities. Computer simulations of the global catalytic model using the measured kinetic parameters produced results that mimicked the measured outcomes, and this provided further insights on the catalytic behaviors of the chimeras and basis of their increased NO dioxygenase activities.
- Wang, Zhi-Qiang,Haque, Mohammad Mahfuzul,Binder, Katherine,Sharma, Manisha,Wei, Chin-Chuan,Stuehr, Dennis J.
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p. 122 - 130
(2016/06/08)
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- β-hairpin peptidomimetics
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β-Hairpin peptidomimetics of the general formula Cyclo(-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-Xaa9-Xaa10-Xaa11-Xaa12-Xaa13-Xaa14-Xaa15-Xaa16-), and pharmaceutically acceptable salts thereof, with Xaa 1-Xaa 16 being amino acid residues of certain types which are defined in the description and the claims, have CXCR4 antagonizing properties and prolonged half-lives in vivo and can be used for preventing HIV infections in healthy individuals or for slowing and halting viral progression in infected patients; or where cancer is mediated or resulting from CXCR4 receptor activity; or where immunological diseases are mediated or resulting from CXCR4 receptor activity; or for treating immunosuppression; or during apheresis collections of peripheral blood stem cells and/or as agents to induce mobilization of stem cells to regulate tissue repair. These peptidomimetics can be manufactured by a process which is based on a mixed solid- and solution phase synthetic strategy.
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- β-hairpin peptidomimetics
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β-Hairpin peptidomimetics of the general formula Cyclo(-Xaa1-Xaa2-Xaa3-Xaa4-Xaa5-Xaa6-Xaa7-Xaa8-Xaa9-Xaa10-Xaa11-Xaa12-Xaa13-Xaa14-), enantiomers and pharmaceutically acceptable salts thereof, with Xaa1-Xaa14 being amino acid residues of certain types which are defined in the description and the claims, have anti-infective activity, e.g. to selectively inhibit the growth of or to kill microorganisms such as Bacillus subtilis and/or Shigella boydii. They can be used as medicaments to treat or prevent infections or as disinfectants for foodstuffs, cosmetics, medicaments or other nutrient-containing materials. These peptidomimetics can be manufactured by a process which is based on a mixed solid- and solution phase synthetic strategy.
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- TEMPLATE-FIXED PEPTIDOMIMETICS WITH CXCR7 MODULATING ACTIVITY
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Novel template-fixed β-hairpin peptidomimetics of the general formula (I), wherein the single elements T or P are α-amino acid residues connected from the carbonyl (C═O) point of attachment to the nitrogen (N) of the next element in clockwise direction and wherein said elements, depending on their positions in the chain, are defined in the description and the claims have the property to act on the receptor CXCR7. Thus, these β-hairpin peptidomimetics can be useful in the treatment or prevention of diseases or conditions in the area of dermatological disorders, metabolic diseases, inflammatory diseases, fibrotic diseases, infectious diseases, neurological diseases, cardiovascular diseases, respiratory diseases, gastro-intestinal tract disorders, urological diseases, ophthalmic diseases, stomatological diseases, haematological diseases and cancer; or the mobilisation of stem cells.
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- A novel preparation of L-citrulline and L-homocitrulline
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L-citrulline was synthesized from L-ornithine monohydrochloride, which was treated with copper salt under alkaline conditions to protect α-NH 2, followed by formylation of δ-NH2 with carbamide, and the removal of copper ion via the combination with sulfides or organic acids to release L-citrulline in satisfactory yield. L-homocitrulline was prepared from L-lysine monohydrochloride with the same method. This new method has the advantages of being environmentally friendly and suitable for industrial production.
- Jia, Gen-Guang,Liu, Yi,Zheng, You-Guang,Zhang, Ling,Liu, Ling,Ling, Xin,Gou, Ling-Shan,Yin, Cui,Zhuang, Xue-Mei
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experimental part
p. 451 - 454
(2012/07/17)
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- PROCESSES FOR THE PRODUCTION OF L-CITRULLINE
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Processes for producing a suitable purity grade of L-Citrulline are disclosed. The processes can include contacting crude L-Citrulline in an aqueous solution with an adsorptive medium at a temperature above approximately 5O0C and below the temperature of denaturement for the L- Citrulline for an interval sufficient to remove at least one contaminant from the L-Citrulline. The processes can also include concentrating the dissolved L- Citrulline relative to the aqueous solution.
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Page/Page column 14-15
(2009/04/25)
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- 4,4-Difluorinated analogues of l-arginine and NG-hydroxy-l-arginine as mechanistic probes for nitric oxide synthase
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4,4-Difluoro-l-arginine and 4,4-difluoro-NG-hydroxy-l-arginine were synthesized and shown to be substrates for the inducible isoform of nitric oxide synthase (iNOS). Binding of both fluorinated analogues to the NOS active site was also investigated using a spectral binding assay employing a heme domain construct of the inducible NOS isoform (iNOSheme). 4,4-Difluoro-NG-hydroxy-arginine was found to bind at the NOS active site in a unique manner consistent with a model involving ligation of the FeIII heme center by the oxygen atom of the NG-hydroxy moiety.
- Martin, Nathaniel I.,Woodward, Joshua J.,Winter, Michael B.,Marletta, Michael A.
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supporting information; body text
p. 1758 - 1762
(2009/11/30)
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- Inactivation of microbial arginine deiminases by L-canavanine
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Arginine deiminase (ADI) catalyzes the hydrolytic conversion of L-arginine to ammonia and L-citrulline as part of the energy-producing L-arginine degradation pathway. The chemical mechanism for ADI catalysis involves initial formation and subsequent hydrolysis of a Cys-alkylthiouronium ion intermediate. The structure of the Pseudomonas aeruginosa ADI-(L-arginine) complex guided the design of arginine analogs that might react with the ADIs to form inactive covalent adducts during catalytic turnover. One such candidate is L-canavanine, in which an N-methylene of L-arginine is replaced by an N-O. This substance was shown to be a slow substrate-producing O-ureido-L-homoserine. An in depth kinetic and mass spectrometric analysis of P, aeruginosa ADI inhibition by L-canavanine showed that two competing pathways are followed that branch at the Cys-alkylthiouronium ion intermediate. One pathway leads to direct formation of O-ureido-L-homoserine via a reactive thiouronium intermediate. The other pathway leads to an inactive form of the enzyme, which was shown by chemical model and mass spectrometric studies to be a Cys-alkylisothiourea adduct. This adduct undergoes slow hydrolysis to form O-ureido-L-homoserine and regenerated enzyme. In contrast, kinetic and mass spectrometric investigations demonstrate that the Cys-alkylthiouronium ion intermediate formed in the reaction of L-canavanine with Bacillus cereus ADI partitions between the product forming pathway (O-ureido-L-homoserine and free enzyme) and an inactivation pathway that leads to a stable Cys-alkylthiocarbamate adduct. The ADIs from Escherichia coli, Burkholderia mallei, and Giardia intestinalis were examined in order to demonstrate the generality of the L-canavanine slow substrate inhibition and to distinguish the kinetic behavior that defines the irreversible inhibition observed with the B. cereus ADI from the time controlled inhibition observed with the P. aeruginosa, E. coli, B. mallei, and G. intestinalis ADIs.
- Li, Ling,Li, Zhimin,Chen, Danqi,Lu, Xuefeng,Feng, Xiaohua,Wright, Elizabeth C.,Solberg, Nathan O.,Dunaway-Mariano, Debra,Mariano, Patrick S.,Galkin, Andrey,Kulakova, Liudmila,Herzberg, Osnat,Green-Church, Kari B.,Zhang, Liwen
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p. 1918 - 1931
(2008/09/18)
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- Metalloporphyrin and heteropoly acid catalyzed oxidation of C=NOH bonds in an ionic liquid: Biomimetic models of nitric oxide synthase
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Water soluble iron(III) porphyrins and phosphotungstic acid in an ionic liquid are effective catalysts for the H2O2 mediated oxidation of the CNOH bond in N-hydroxyarginine and other oximes. The carbonyl compounds generated as the oxidation products can be easily isolated from the reaction media. These systems serve as biomimetic models of nitric oxide synthase (NOS) and the catalyst immobilized in an ionic liquid can be easily recycled and reused.
- Jain, Nidhi,Kumar, Anil,Chauhan, Shive M.S.
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p. 2599 - 2602
(2007/10/03)
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- Nitrocatechols versus nitrocatecholamines as novel competitive inhibitors of neuronal nitric oxide synthase: Lack of the aminoethyl side chain determines loss of tetrahydrobiopterin-antagonizing properties
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6-Nitrocatecholamines were recently described as novel neuronal nitric oxide synthase inhibitors competing with both L-arginine and tetrahydrobiopterin (BH4). We report now that simple nitrocatechols are also competitive inhibitors, lacking however BH4-antagonizing properties. It is argued that 6-nitrocatecholamines interact with the L-arginine- and BH4-binding sites through the nitrocatechol and aminoethyl moieties, respectively.
- Palumbo, Anna,Napolitano, Alessandra,D'Ischia, Marco
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- METHOD OF TREATMENT AND PREVENTION OF NITRIC OXIDE DEFICIENCY-RELATED DISORDERS WITH CITRULLINE AND CITRULLINE DERIVATIVES
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The invention provides methods for control, management, treatment and prevention of conditions related to nitric oxide deficiency such as hypertension, cardiovascular disease, osteoporosis, diabetes mellitus, preeclampsia HELLP, syndrome and fetal growth retardation; uterine contractility disorders such as preterm labor and dysmenorrhea, cervical dystocia, infertility and early pregnancy loss; male impotence; urinary incontinence; intestinal tract disorders (e.g. altered motility and pyloric stenosis), respiratory system diseases (e.g. asthma, neonatal respiratory distress syndrome, pulmonary hypertension, and adult respiratory distress syndrome); inflammatory diseases (e.g. acute inflammation, resistance to infection, SLE-lupus, anaphylactic reaction, allograft rejection); Alzheimer's disease, stroke, growth hormone disorders, and behavior changes; dermatological conditions such as atopic eczema, topical hair loss, and burn injury; by administering citrulline or a citrulline analogue, optionally in combination with other enhancing or modulating agents, e.g., an estrogenic, partial estrogenic, progestagenic, or androgenic agent, and pharmaceutical preparations for such uses.
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- Deuterium isotope effects and product studies for the oxidation of N(ω)-allyl-L-arginine and N(ω)-allyl-N(ω)-hydroxy-L-arginine by neuronal nitric oxide synthase
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The nitric oxide synthases (NOS), which require heme, tetrahydrobiopterin, FMN, FAD, and NADPH, catalyze the O2-dependent conversion of L-arginine to L-citrulline and nitric oxide. N(ω)-Allyl-L-arginine, a mechanism-based inactivator of neuronal NOS, also is a substrate, producing L-arginine, acrolein, and H2O (Zhang, H. Q.; Dixon, R. P.; Marletta, M. A.; Nikolic, D.; Van Breemen, R.; Silverman, R. B. J. Am. Chem. Soc. 1997, 119, 10888). Two possible mechanisms for this turnover are proposed, one initiated by allyl C-H bond cleavage and the other by guanidino N-H cleavage, and these mechanisms are investigated with the use of N(ω)-allyl-L-arginine (1), N(ω)-[1,1-2H2]allyl-L-arginine (7), N(ω)-allyl-N(ω)-hydroxy-L-arginine (2) and N(ω)-[1,1-2H2]allyl-N(ω)-hydroxy-L-arginine (8) as substrates. Significant isotope effects on the two kinetic parameters, k(cat) and k(cat)/K(m), are observed in case of 1 and 7 during turnover, but not with 2 and 8. No kinetic isotope effects are observed for either compound in their role as inactivators. These results support a mechanism involving initial C-H bond cleavage of N(ω)-allyl-L-arginine followed by hydroxylation and breakdown to products. Copyright (C) 2000.
- Hah, Jung-Mi,Roman, Linda J.,Silverman, Richard B.
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p. 1931 - 1936
(2007/10/03)
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- Parenteral nutrition therapy with amino acids
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Parenteral nutrition aqueous solutions are provided which preferably contain glutamine together with other organic nitrogen containing compounds. The respective concentrations of the compounds present in any given such solution are typically approximately multiples of the concentration of the same compounds as found in normal human plasma, and the respective mole ratios of various such compounds in any given such solution relative to one another are approximately the same mole ratio associated with the same compounds as found in normal human plasma. Processes for using such solutions are provided.
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- Cosmetic composition
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A composition suitable for topical application to mammalian skin and hair for inducing, maintaining or increasing hair growth comprises a hair growth promoter chosen from glutamine derivatives and salts thereof. The composition preferably also comprises an activity enhancer which may be chosen from hair growth stimulants, penetration enhancers and cationic polymers.
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- Thermochemistry of the hydrolysis of L-arginine to (L-citrulline + ammonia) and of the hydrolysis of L-arginine to (L-ornithine + urea)
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Molar enthalpies of reaction for the hydrolysis of L-arginine(aq) to and for the hydrolysis of L-arginine(aq) to have been measured by microcalorimetry.These reactions are catalyzed, respectively, by arginase and by arginine deiminase.The effects of variations in pH, temperature, and ionic strength on the molar enthalpies of reaction were studied.The results have been analyzed with a model which accounts for the complex equilibria in solution.The results obtained at T = 298.15 K for the reference reactions are: ΔfHm0 = -(21.4+/-0.5) kJ * mol-1 for L-arginine+(aq) + H2O(l) = L-ornithine+(aq) + urea(aq) and ΔfHm0 = -(31.9+/-0.8) kJ * mol-1 for L-arginine+(aq) + H2O(l) = L-citrulline(aq) + NH4+(aq).These results are discussed in terms of thermodynamic-cycle calculations and in terms of the metabolic urea cycle.
- Tewari, Y. B.,Kishore, N.,Margolis, S. A.,Goldberg, R. N.,Shibatani, T.
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p. 293 - 305
(2007/10/02)
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- Urea cycle: Chemical simulation of arginine biosynthesis
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We have successfully simulated the salient features of the urea cycle. In this effort an appropriately protected ornithine was transformed to citrulline, via use of a novel amide transfer reagent; the citrulline, in turn, was converted into argininosuccinate which necessitated a new activation procedure to enable acceptance of dimethyl aspartate. Fragmentation of argininosuccinate under carefully controlled conditions afforded arginine. The final step in the cycle, namely, the hydrolysis of arginine to urea and ornithine, has already been accomplished. Amino group transfer from aspartate has also been demonstrated in the conversion of hypoxanthine to adenine.
- Ranganathan,Rathi
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p. 2351 - 2354
(2007/10/02)
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