A new access to alkyl-α-ketoglutaric acids, precursors of glutamic acid analogues by enzymatic transamination. Application to the synthesis of (2S,4R)-4-propyl-glutamic acid
摘要:
4-Alkyl-2-alkylidene-glutaric acids are easily obtained by a Claisen-Johnson rearrangement, providing a short access to 4-alkyl-alpha-ketoglutaric acids. These compounds are substrates of the glutamic oxalacetic transaminase (GOT), allowing the enzymatic synthesis of biologically important analogues of L-glutamate. A new analogue, (2S,4R)-4-propyl-glutamic acid, is described. (C) 1999 Elsevier Science Ltd. All rights reserved.
Kinetics and Mechanism for the Reaction of Cysteine with Hydrogen Peroxide in Amorphous Polyvinylpyrrolidone Lyophiles
作者:Dayong Luo、Bradley D. Anderson
DOI:10.1007/s11095-006-9052-z
日期:2006.10.4
PURPOSE: Peroxide impurities play a critical role in drug oxidation. In metal-free aqueous solutions, hydrogenperoxide (H(2)O(2)) induced thiol oxidation involves a bimolecular nucleophilic reaction to form a reactive sulfenic acid intermediate (RSOH), which reacts with a second thiol to form a disulfide (RSSR). This study examines the reaction of cysteine (CSH) and H(2)O(2) in amorphous polyvinylpyrrolidone
Antioxidant Chemistry: Oxidation of <scp>l</scp>-Cysteine and Its Metabolites by Chlorite and Chlorine Dioxide
作者:James Darkwa、Rotimi Olojo、Edward Chikwana、Reuben H. Simoyi
DOI:10.1021/jp049748k
日期:2004.7.1
The oxidation of l-cysteine and its metabolites cystine and l-cysteinesulfinic acid by chlorite and chlorine dioxide has been studied in unbuffered neutral and slightly acidic media. The stoichiometry of the oxidation of l-cysteine was deduced to be 3ClO2- + 2H2NCH(COOH)CH2SH → 3Cl- + 2H2NCH(COOH)CH2SO3H with the final product as cysteic acid. The stoichiometry of the chlorite−cysteinesulfinic acid
Antioxidant chemistry Reactivity and oxidation of DL-cysteine by some common oxidants
作者:James Darkwa、Claudius Mundoma and Reuben H. Simoyi
DOI:10.1039/a708863i
日期:——
The reactivity of DL-cysteine, a physiologically important aminothiol, was studied by reacting it with several well known oxidants.No activity was observed on the amino and carboxyl groups. The only reactivity of physiological significance was at the sulfur centre. Reactions of cysteine with hydrogen peroxide show that the thiol group is capable of mopping up free radicals by forming thyl radicals, as expected in its role as an antioxidant. A four-electron oxidation of cysteine gave reasonably stable cysteine sulfinic acid. Oxidants in the form of peracids do oxidize cysteine only as far as the sulfinic acid. Stronger oxidizing agents can oxidize cysteine as far as the cysteine sulfonic acid. No further oxidation can be detected as the C–S bond is not cleaved. The inertness of the amino group in cysteine makes it incapable of reversibly mopping up the dangerous oxyhalogens HOCl and HOBr which are produced by myeloperoxidase-catalysed oxidation of halides by hydrogen peroxide, as is the case with taurine. A detailed mechanism, together with a computer simulation study of the oxidation of cysteine by acidified bromate, is proposed.
Method for determining the presence of an aminotransferase (AT.sub.1), other than aspartate aminotransferase (AST), in a biological sample. The method includes contacting the sample with an amino donor substrate for AT.sub.1, an amino acceptor substrate for AT.sub.1, cysteine sulfinic acid (CSA) in excess, a second aminotransferase (AT.sub.2), different from AT.sub.1, in excess, and an indicator for the presence of sulfite ions, under conditions in which the concentration of said AT.sub.1 can be determined by the amount of the indicator which forms a detectable signal.
The Cysteine Dioxygenase Homologue from Pseudomonas aeruginosa Is a 3-Mercaptopropionate Dioxygenase
作者:Egor P. Tchesnokov、Matthias Fellner、Eleni Siakkou、Torsten Kleffmann、Lois W. Martin、Sekotilani Aloi、Iain L. Lamont、Sigurd M. Wilbanks、Guy N.L. Jameson
DOI:10.1074/jbc.m114.635672
日期:2015.10
Thiol dioxygenation is the initial oxidation step that commits a thiol to important catabolic or biosynthetic pathways. The reaction is catalyzed by a family of specific non-heme mononuclear iron proteins each of which is reported to react efficiently with only one substrate. This family of enzymes includes cysteine dioxygenase, cysteamine dioxygenase, mercaptosuccinate dioxygenase, and 3-mercaptopropionate dioxygenase. Using sequence alignment to infer cysteine dioxygenase activity, a cysteine dioxygenase homologue from Pseudomonas aeruginosa (p3MDO) has been identified. Mass spectrometry of P. aeruginosa under standard growth conditions showed that p3MDO is expressed in low levels, suggesting that this metabolic pathway is available to the organism. Purified recombinant p3MDO is able to oxidize both cysteine and 3-mercaptopropionic acid in vitro, with a marked preference for 3-mercaptopropionic acid. We therefore describe this enzyme as a 3-mercaptopropionate dioxygenase. Mossbauer spectroscopy suggests that substrate binding to the ferrous iron is through the thiol but indicates that each substrate could adopt different coordination geometries. Crystallographic comparison with mammalian cysteine dioxygenase shows that the overall active site geometry is conserved but suggests that the different substrate specificity can be related to replacement of an arginine by a glutamine in the active site.