Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.5.1.47 (cysteine synthase)
 625 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The inhibition of Salmonella typhimurium by 1,2,4-triazole appears to be mediated through an effect on L-cysteine biosynthesis. O-Acetylserine sulfhydrylase A, the final enzyme in the L-cysteine biosynthetic pathway, was found to catalyze a reaction (triazolylase) between O-acetyl-L-serine and 1,2,4-triazole, giving 1,2,4-triazole-1-alanine as a product. In wild type S. typhimurium grown on 4 mM 1,2,4-triazole, 97% of the total O-acetyl-L-serine synthesized in vivo is incorporated into 1,2,4-triazole-1-alanine. 1,2,4-triazole also significantly lowers the levels of several of the enzymes necessary for sulfate reduction. This effect is presumably due to the ability of the inhibitor to lower intracellular concentrations of O-acetyl-L-serine, an inducer of these enzymes. Inhibition of growth is probably caused by L-cysteine starvation, arising from the decreased availability of the L-cysteine precursors, sulfide and O-acetyl-L-serine. Two 1,2,4-triazole-resistant strains bearing mutations in cysK, the structural gene for O-acetylserine sulfhydrylase A, incorporate only small quantities of O-acetyl-L-serine into 1,2,4-triazole-1-alanine in vivo. In vitro studies, using purified preparations of O-acetylserine sulfhydrylase A, revealed greater losses of triazolylase activity than sulfhydrylase activity in the enzymes from both cysK mutants. Resistance to 1,2,4-triazole apparently can arise from mutations leading to a preferential loss of triazolylase activity or from mutations which diminish both activities to the extent that high concentrations of O-acetyl-L-serine and sulfide accumulate behind the sulfhydrylase reaction.
J Biol Chem 1975 Sep 25
PMID:Studies on the mechanism of inhibition of Salmonella typhimurium by 1,2,4-triazole. 110 Jun 24

1. The maximum activities of the enzymes for the biosynthesis of GSH (gamma-glutamyl-cysteine synthetase and GSH synthetase) have been assayed in high GSH and low GSH erythrocytes from Tasmanian Merino and Finnish Landrace sheep. 2. For the Merinos, the activities (mumol product/g haemoglobin per min +/- S.E.M. (n)) in the high and low GSH erythrocytes respectively were: gamma-glutamyl-cysteine synthetase: 0.776 +/- 0.065 (11) and 0.375 +/- 0.063 (13); and GSH synthetase: 0.069 +/- 0.003 (11) and 0.066 +/- 0.002 (13). 3. For the Finnish Landrace sheep the activities in the high and low GSH erythrocytes respectively were: gamma-glutamyl-cysteine synthetase: 0.595 +/- 0.063 (12) and 0.555 +/- 0.033 (10) and gamma-glutamyl-cysteine synthetase: 0.073 +/- 0.002 (12) and 0.070 +/- 0.002 (10). 4. gamma-Glutamyl-cysteine synthetase was markedly inhibited by physiological GSH concentrations. No evidence was found for the presence of an inhibitor of GSH biosynthesis (other than GSH) in low GSH erythrocytes from Finnish Landrace sheep. 5. Although for the Merinos the low GSH trait can be explained in terms of a diminished activity of gamma-glutamyl-cysteine synthetase, no such explanation is tenable for the Finnish Landrace sheep.
Biochim Biophys Acta 1975 Sep 08
PMID:GSH biosynthesis in glutathione deficient erythrocytes from Finnish landrace and Tasmanian merino sheep. 117 55

Cysteine synthase (O-acetylserine sulfhydrylase) has been purified to homogeneity from bell pepper (Capsicum annuum) fruit chromoplasts. This enzyme consists of two subunits of 35 kDa. Immunocytochemical localization experiments confirmed the plastid location of this enzyme. A full-length cDNA was isolated from an expression library of C. annuum. The deduced peptide sequence revealed high similarity between the C. annuum cysteine synthase and its bacterial counterparts. In vitro transcription and translation of the cDNA and subsequent import experiments demonstrated that the encoded cysteine synthase is located in the plastids. The steady-state level of the cysteine synthase mRNA is almost constant in dark-grown hypocotyls, leaves, and fruits. However, a slight increase in this mRNA level was detected during fruit development (when the 25 S rRNA was taken as an internal standard). Similarly, the cysteine synthase activity in plastids was found to increase during fruit development and reaches the highest levels in the chromoplasts of red fruits. To address the physiological role of this phenomenon, we have shown that cysteine is engaged in the active metabolism of glutathione. Thus, in connection with the previous demonstration of an active tocopherol metabolism, it is concluded that differentiation of chloroplast to chromoplast in C. annuum involves an active synthesis of potential antioxidants or redox modulators.
J Biol Chem 1992 Sep 05
PMID:Cysteine synthase from Capsicum annuum chromoplasts. Characterization and cDNA cloning of an up-regulated enzyme during fruit development. 138 58

Cysteine synthase (CSase) [O-acetyl-L-serine acetate-lyase (adding hydrogen sulfide), EC 4.2.99.8] catalyzes the formation of L-cysteine, the key step in sulfur assimilation in plants, from O-acetyl-L-serine and hydrogen sulfide. We report here the isolation and characterization of cDNA clones encoding cysteine synthase from spinach (Spinacia oleracea L.). Internal peptide sequences were obtained from V8 protease-digested fragments of purified CSase. A lambda gt10 cDNA library was constructed from poly(A)+ RNA of young green leaves of spinach. Screening with two synthetic mixed nucleotides encoding the partial peptide sequences revealed 19 positively hybridized clones among 2 x 10(5) clones. Nucleotide sequence analysis of two independent cDNA clones revealed a continuous open reading frame encoding a polypeptide of 325 amino acids with a calculated molecular mass of 34,185 Da. Sequence comparison of the deduced amino acids revealed 53% identity with CSases of Escherichia coli and Salmonella typhimurium. Sequence homology was also observed with other metabolic enzymes for amino acids in bacteria and yeast and with rat hemoprotein H-450. A bacterial expression vector was constructed and could genetically complement an E. coli auxotroph that lacks CSases. The accumulation of functionally active spinach CSase in E. coli was also demonstrated by immunoblotting and assaying enzymatic activity. Southern hybridization analysis showed the presence of two to three copies of the cDNA sequence in the genome of spinach. RNA blot hybridization suggested constitutive expression in leaves and roots of spinach.
Proc Natl Acad Sci U S A 1992 Sep 01
PMID:Molecular cloning and bacterial expression of cDNA encoding a plant cysteine synthase. 151 33

An improved method for purifying O-acetylserine sulfhydrylase from Salmonella typhimurium is described as well as a new computer-controlled assay making use of the sulfide ion selective electrode. The purification method uses gradient elution from Q-Sepharose Fast Flow and phenyl-Sepharose columns to give 75 mg (50% yield) of the enzyme starting from 300 g of starting material in 3 days. The sulfide electrode assay makes use of sulfide and calomel electrodes attached to a signal buffer which serves as an impedance match. The output of the signal buffer is linked in parallel to a strip chart recorder and a Keithley Model 575 data acquisition and control system. The system 575 is interfaced to a Packard-Bell AT computer. In addition, two BASIC computer programs have been written to convert potential measured by the electrode to sulfide concentration and to convert the time course data to rates.
Protein Expr Purif 1990 Sep
PMID:A rapid purification procedure and computer-assisted sulfide ion selective electrode assay for O-acetylserine sulfhydrylase from Salmonella typhimurium. 215 86

In order to obtain inhibitors of the meso-diaminopimelate-adding enzyme, which participates in the biosynthesis of bacterial peptidoglycan, several N alpha-propionyl-dipeptides of the general formula Pr-L-Ala-ambo-Xaa-OH were synthesized. Xaa represented methionine S,S-dioxide, methionine S-oxide, methionine sulfoximine, and 2-amino-4-phosphonobutyric acid, i.e. transition state analogs of glutamine synthetase and gamma-glutamyl-cysteine synthetase, which catalyze the same type of reaction as our target enzyme. After synthesis, the diastereoisomers were separated by preparative HPLC or t.l.c.; those containing methionine derivatives could be identified thanks to previously synthesized reference compounds. After preincubation with the meso-diaminopimelate-adding activity from Escherichia coli, the LD diastereoisomers displayed moderate inhibitory effects, whereas the LL ones were inefficient. The best inhibition was obtained with one diastereoisomer of Pr-L-Ala-zeta-2-amino-4-phosphonobutyrate, presumably the LD one. A chloromethylketone derivative Pr-L-Ala-D-Glu(CH2Cl)-OH, potential affinity labeler of the meso-diaminopimelate-adding enzyme, was also synthesized. In the assay with preincubation, this compound behaved as the best inhibitor.
Int J Pept Protein Res 1988 Sep
PMID:Synthesis of inhibitors of the meso-diaminopimelate-adding enzyme from Escherichia coli. 307 5

A mutagenic azide metabolite was purified from the medium in which Salmonella typhimurium cells were grown in the presence of azide. This metabolite was identified to be azidoalanine based on infrared and mass spectroscopy and elemental analysis. This compound appeared to be identical to the mutagenic compound synthesized in vitro from azide and O-acetylserine by partially purified O-acetylserine sulfhydrylase. The metabolite (azidoalanine) mutagenic efficiency and spectrum in S. typhimurium was similar to that of inorganic azide. The compounds 2-azidoethylamine, 2-bromoethylamine, 3-bromopropionic acid and N-(azidomethyl) phthalimide were also mutagenic with a similar spectrum to azide and azidoalanine, but with lower efficiency. The compounds 3-azidopropylamine, 4-azidobutylamine, 3-chloroalanine and ethylamine were only weakly or nonmutagenic. Numerous other chloro, bromo and azido phthalimide derivatives tested were nonmutagenic. It is suggested that the lack of azide mutagenicity (and perhaps carcinogenicity) in mammalian cells may be due to their inability to convert azide to azidoalanine.
Mutat Res 1983 Sep
PMID:A mutagenic metabolite synthesized by Salmonella typhimurium grown in the presence of azide is azidoalanine. 635 13

The O-acetylserine sulfhydrylase (OASS) reaction has been studied using a number of spectral probes including UV--visible, fluorescence, circular dichroism, and 31P NMR spectroscopy. The addition of L-cysteine, L-alanine, and glycine to OASS results in a shift in lambda max of 412 nm for the internal Schiff base to 418 nm resulting from the formation of the external Schiff base. The addition of L-serine or O-methyl-D,L-serine gives decreases of the absorbance of unliganded enzyme at 412 nm of about 50% and 20%, respectively, concomitant with an increase in the absorbance at 320 nm and a shift in the lambda max of the remaining visible absorbance to 418 nm. The spectral shifts observed in the presence of L-serine are suggestive of establishing an equilibrium between different forms of external Schiff base. The concentration dependence of the changes at 440 (L-cysteine) and 320 nm (L-serine) provides an estimate of the dissociation constant for the external aldimine. The pH dependence of the dissociation constant suggests the alpha-amine of the amino acid must be unprotonated for nucleophilic attack at C4' of PLP, and an enzyme side chain must be unprotonated to hydrogen-bond the thiol or hydroxyl side chain of the amino acid. When L-cysteine is the amino acid, the thiol side chain must be protonated to hydrogen-bond to the unprotonated enzyme side chain. The 31P NMR chemical shift is increased from 5.2 ppm for unliganded enzyme to 5.3 ppm in the presence of L-cysteine, signaling a tighter interaction at the 5'-phosphate upon formation of the external Schiff base.(ABSTRACT TRUNCATED AT 250 WORDS)
Biochemistry 1995 Sep 26
PMID:Identification and spectral characterization of the external aldimine of the O-acetylserine sulfhydrylase reaction. 754 55

The pH dependence of kinetic parameters using natural and alternative reactants was determined in order to obtain information on the chemical mechanisms of the A and B isozymes of O-acetylserine sulfhydrylase (OASS) from Salmonella typhimurium. A general mechanism is proposed for OASS in which OAS binds with its alpha-amine unprotonated to carry out a nucleophilic attack on C4' of the protonated Schiff base and with the acetyl carbonyl hydrogen-bonded to a protonated enzyme group (or a water molecule), which aids in the beta-elimination of acetate. The enzyme lysine that was in Schiff base linkage with the active site pyridoxal 5'-phosphate deprotonates the alpha-carbon in the beta-elimination reaction, and a proton is likely released with the acetate product. Sulfide likely binds as HS- to undergo nucleophilic attack on the alpha-aminoacrylate intermediate, followed by protonation of the alpha-carbon by the enzyme lysine. In OASS-A, HS- is hydrogen-bonded to the enzyme group that assists in the beta-elimination of acetate, but this is not the case for OASS-B. The pH independent equilibrium constant for the first half-reaction of OASS-A is 1.6 x 10(-3), while the second half-reaction is practically irreversible.
Biochemistry 1995 Sep 26
PMID:Acid-base chemical mechanism of O-acetylserine sulfhydrylases-A and -B from pH studies. 754 74

Three types of cysteine synthase (CSase, EC 4.2.99.8) isozymes were purified from spinach leaves. Each isozyme was isolated to homogeneity by preparative PAGE. These isozymes were revealed to have different primary structures by amino-acid and proteinase digestion analyses, respectively. The enzymes designated as CSase 1, CSase 2 and CSase 3 with reference to the mobility on native PAGE were characterized with respect to physicochemical and enzymatic properties, and it was found that those enzymes had similar properties. It was also found that CSase 1 could be attributed to chloroplasts.
Biochim Biophys Acta 1995 Sep 06
PMID:Comparative studies on cysteine synthase isozymes from spinach leaves. 766 16


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