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)

L-Cystine and L-cysteine specifically reverse the mutagenic action of azide in Salmonella typhimurium and Escherichia coli. To establish whether the L-cysteine biosynthetic pathway is involved in azide-induced mutagenesis, several derivatives of a mutagen tester-strain of S. typhimurium bearing mutations in different cys genes were isolated. No mutagenic effect of azide was observed in a strain carrying mutation in the cysE gene, unless the incubation medium was supplemented with exogenous O-acetylserine. Our of 16 cysK mutants 14 were mutagenized by azide very poorly or not at all. These results indicate that the activity of O-acetylserine sulfhydrylase A, and the availability of O-acetylserine, one of the two co-substrates of the enzyme, are essential for the mutagenic action of azide in S. typhimurium.
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PMID:Involvement of the L-cysteine biosynthetic pathway in azide-induced mutagenesis in Salmonella typhimurium. 699 14

Studies with crude preparations obtained from a cysteine auxotroph of Saccharomyces cerevisiae showed that O-acetylserine sulfhydrylase could be separated from O-acetylhomoserine sulfhydrylase by chromatography on a DEAE-cellulose column and centrifugation in a sucrose density gradient. On the basis of sedimentation distance, the molecular weights of these enzymes were calculated to be about 99,000 and 182,000, respectively. The former did not react with the amino acid substrate of the latter, and vice versa. The wild-type strain was also demonstrated to possess O-acetylserine sulfhydrylase (molecular weight: about 96,000), in addition to a large amount of O-acetylserine-O-acetylhomoserine sulfhydrylase (Yamagata et al. (1974) J. Biochem. 75, 1221).
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PMID:Occurrence of low molecular weight O-acetylserine sulfhydrylase in the yeast Saccharomyces cerevisiae. 700 60

O-Acetyl-L-serine sulfhydrylase catalyzes the final step in the biosynthesis of cysteine from H2S and O-acetyl-L-serine in the fungus Cephalosporsium acremonium, a cephalosporin C-producing organism. We separated this enzyme from the closely related but less specific O-acetyl-L-homoserine sulfhydrylase and showed that O-acetyl-L-homoserine sulfhydrylase also catalyzes the formation of cysteine from O-acetyl-L-serine and H2S. The expression of O-acetyl-L-serine sulfhydrylase was regulated by exogenous methionine. In addition, this enzyme was inhibited by S-adenosyl-L-methionine and 5-formylpteroyl monoglutamic acid. The inhibition of both S-adenosyl-L-methionine and 5-formylpteroyl monoglutamic acid was noncompetitive. Results obtained with gel filtraton experiments in various buffer systems indicate an association-dissociation behavior of O-acetyl-L-serine sulfhydrylase.
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PMID:Regulatory properties of O-acetyl-L-serine sulfhydrylase of Cephalosporium acremonium: evidence of an isoenzyme and its importance in cephalosporin C biosynthesis. 719 Dec 38

Extracts of Desulfovibrio vulgaris were found to contain serine transacetylase and cysteine synthase activities. When extracts were incubated with bisulfite and o-acetylserine, or acetyl coenzyme A plus L-serine, under a hydrogen atmosphere, cysteine was formed. Pyruvate served as a reductant for bisulfite reduction to sulfide and concomitantly provided the acetyl moiety for acetyl coenzyme A formation. Consequently, when extracts were incubated with pyruvate, bisulfite, and L-serine, cysteine synthesis resulted.
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PMID:Cysteine synthesis by Desulfovibrio vulgaris extracts. 736 31

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)
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PMID:Identification and spectral characterization of the external aldimine of the O-acetylserine sulfhydrylase reaction. 754 55

Serine acetyltransferase (SATase; EC 2.3.1.30), which catalyzes the reaction connecting serine and cysteine/methionine metabolism, plays a regulatory role in cysteine biosynthesis in plants. We have isolated a cDNA clone encoding SATase by direct genetic complementation of a Cys- mutation in Escherichia coli using an expression library of Citrullus vulgaris (watermelon) cDNA. The cDNA encodes a polypeptide of 294 amino acids (31,536 Da) exhibiting 51% homology with that of E. coli SATase. DNA-blot analysis indicated the presence of a single copy of the SATase gene (sat) in watermelon. RNA hybridization analysis suggested the relatively ubiquitous and preferential expression in the hypocotyls of etiolated seedlings. Immunoblot analysis indicated the accumulation of SATase predominantly in etiolated plants. L-Cysteine, an end product of the cysteine biosynthetic pathway, inhibited the SATase in an allosteric manner, indicating the regulatory function of SATase in this metabolic pathway, whereas beta-(pyrazole-1-yl)-L-alanine, a secondary metabolite formed partly through the cysteine biosynthetic pathway, showed no inhibitory effect. A multi-enzyme complex was formed from recombinant proteins of SATase and cysteine synthase (O-acetylserine(thiol)-lyase) from watermelon, suggesting efficient metabolic channeling from serine to cysteine, preventing the diffusion of intermediary O-acetyl-L-serine.
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PMID:Molecular cloning and characterization of a plant serine acetyltransferase playing a regulatory role in cysteine biosynthesis from watermelon. 760

The coding sequences of the cysE and cysK genes from Escherichia coli, which encode the enzymes of the cysteine biosynthetic pathway, namely, serine acetyltransferase (EC 2.3.1.30) and O-acetylserine sulfhydrylase (or cysteine synthase [EC 4.2.99.8]), were modified for expression in eukaryotic cells and introduced into murine L cells. A number of fusion genes comprising the cysE or cysK coding sequences joined to the promoter of the ovine metallothionein-Ia (MT-Ia) gene and various portions of the ovine growth hormone (GH) gene were prepared. Significant differences in the level of transcription were observed, depending on the amount and arrangement of the GH gene sequences used, the highest levels being obtained with the constructs MTCE10 and MTCK7, which contained only the GH 3' untranslated gene sequences. These two constructs were fused to produce the gene MTCEK1. In this single DNA sequence, each bacterial gene is under independent MT-Ia promoter control. Expression of the cysK sequence in this construct (MT-Ia promoter-cysE-3' GH sequence-MT-Ia promoter-cysK-3' GH sequence) was elevated compared with expression of the cysK gene in MTCK7. However, expression of the cysE sequence in MTCEK1 was only 40% of that of the cysE gene cloned into MTCE10. The double-promoter configuration, which enhances the expression of the second gene in MTCEK1, is proposed as a model for the modification of bacterial genes in general.
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PMID:Introduction and expression of the bacterial genes cysE and cysK in eukaryotic cells. 768 85

1-Cyano-2-hydroxy-3-butene (CHB), an aliphatic nitrile found in cruciferous vegetables, causes a two- and sevenfold elevation in reduced glutathione (GSH) in rat liver and pancreas, respectively, after oral administration of 200 mg/kg. While this dose is also associated with pancreatotoxicity, a single 100 mg/kg dose or multiple lesser doses show the same effect, although somewhat reduced in magnitude, with no concomitant toxicity. In an attempt to identify the mechanism of this increase, we investigated the effect of CHB on GSH synthesis by examining the effect of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, on CHB-induced GSH elevation. Male Fischer 344 rats received 3 mmol BSO/kg ip 24 and 34 hr following CHB or corn oil. The CHB-mediated elevation in hepatic and pancreatic GSH was eradicated by BSO, suggesting that increased synthesis was responsible. The rate-limiting step in synthesis is gamma-glutamyl cysteine synthetase (GCS); the limiting substrate is cysteine. Therefore, CHB effects on GCS activity and hepatic and pancreatic cysteine equivalents were investigated. When rats were treated by gavage with CHB (100 mg/kg), hepatic GCS mRNA concentrations were increased 24 hr after treatment and hepatic cysteine equivalents were significantly elevated 4 hr following CHB. No significant elevation in hepatic GCS activity was observed, however, even 24 hr following CHB. Pancreatic cysteine equivalents were elevated at both 4 and 8 hr after CHB treatment. However, there was no detectable GCS mRNA or activity in pancreas, in either control or treated animals. Furthermore, CHB had no direct effect on the activity of GCS purified from kidney, regardless of whether GSH was present or absent. These results suggest that the mechanism of CHB-mediated induction of GSH may involve early increases in GSH precursors as well as a later increase in GCS mRNA. The mechanism of GSH elevation identified in these studies may hold therapeutic or prophylactic implications.
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PMID:Differential effect of cyanohydroxybutene on glutathione synthesis in liver and pancreas of male rats. 790 18

Strains of Escherichia coli lacking serine transacetylase or a positive regulator (Cys B protein) of the assimilatory sulfate reduction (ASR) pathway were unable to assimilate sulfonate-S, while single mutants in O-acetyl-L-serine sulfhydrylase (either 'A' or 'B') were able to do so. Mutants unable to reduce sulfate to sulfite were nonetheless able to form and accumulate sulfide and then cysteine from sulfonates, while strains lacking sulfite reductase were not. Thus terminal portions of the ASR pathway are involved in reduction of sulfonate-S to that of cysteine. E. coli K-12 formed cysteine more slowly, and accumulated lesser amounts of it with sulfonate-sulfur than it did from either sulfate or sulfite. These observations are consistent with our earlier report that sulfate is the preferred sulfur source when present simultaneously with a sulfonate.
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PMID:Sulfonate-sulfur utilization involves a portion of the assimilatory sulfate reduction pathway in Escherichia coli. 798 97

We have isolated cDNA clones encoding cysteine synthase (CSase, EC 4.2.99.8), which catalyzes the terminal step in cysteine biosynthesis, by direct genetic complementation of a Cys- mutation in Escherichia coli with an expression library of Citrullus vulgaris (watermelon) cDNA. The library was constructed from 8-day-old etiolated seedlings of C. vulgaris in the lambda ZAPII vector, converted to a plasmid library by in vivo excision, and then used for transformation of cysteine auxotroph E. coli NK3, which lacks the cysK and cysM loci. The complementing cDNA containing a 560 bp 5'-untranslated region encodes a polypeptide of 325 amino acids of M(r) 34342. The translational product reacted with an antibody raised against CSase A of Spinacia oleracea. CSase and beta-pyrazolealanine synthase activities were demonstrated in vitro in extracts from E. coli cells expressing the cDNA. Genomic DNA blot analysis indicated the presence of a single copy of the gene, designated cysA, in the C. vulgaris genome. RNA blot hybridization indicated constitutive expression of cysA in cotyledons, hypocotyls and radicles of green and etiolated seedlings. These data suggested that this cDNA clone encodes CSase A the homolog of which in spinach is localized in the cytoplasm. The molecular phylogenetic tree of the amino acid sequences of CSases from plants and bacteria suggested that there are three families in the CSase superfamily; the plant CSase A family, the plant CSase B family and the bacterial CSase family. The proteins in the plant CSase A family are the most conserved relative to the ancestral CSase protein.
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PMID:Molecular cloning of a cysteine synthase cDNA from Citrullus vulgaris (watermelon) by genetic complementation in an Escherichia coli Cys- auxotroph. 804 62


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