Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.1.22 (cystathionine beta-synthase)
 965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Little is known about the genes and enzymes involved in sulfur assimilation in Bacillus subtilis, or about the regulation of their expression or activity. To identify genes regulated by sulfur limitation, the authors used two- dimensional (2D) gel electrophoresis to compare the proteome of a wild-type strain grown with either sulfate or glutathione as sole sulfur source. A total of 15 proteins whose synthesis is modified under these two conditions were identified by matrix-assisted laser desorption/ionization time of flight (MALDI TOF) mass spectrometry. In the presence of sulfate, an increased amount of proteins involved in the metabolism of C(1) units (SerA, GlyA, FolD) and in the biosynthesis of purines (PurQ, Xpt) and pyrimidines (Upp, PyrAA, PyrF) was observed. In the presence of glutathione, the synthesis of two uptake systems (DppE, SsuA), an oxygenase (SsuD), cysteine synthase (CysK) and two proteins of unknown function (YtmI, YurL) was increased. The changes in expression of the corresponding genes, in the presence of sulfate and glutathione, were monitored using slot-blot analyses and lacZ fusions. The ytmI gene is part of a locus of 12 genes which are co-regulated in response to sulfur availability. This putative operon is activated by a LysR-like regulator, YTLI: This is the first regulator involved in the control of expression in response to sulfur availability to be identified in B. subtilis.
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PMID:Sulfur-limitation-regulated proteins in Bacillus subtilis: a two-dimensional gel electrophoresis study. 1139 Jun 94

Trichomonas vaginalis is an early divergent eukaryote with many unusual biochemical features. It is an anaerobic protozoan parasite of humans that is thought to rely heavily on cysteine as a major redox buffer, because it lacks glutathione. We report here that for synthesis of cysteine from sulfide, T. vaginalis relies upon cysteine synthase. The enzyme (TvCS1) can use either O-acetylserine or O-phosphoserine as substrates. The K(m) values of the enzyme for sulfide are very low (0.02 mm), suggesting that the enzyme may be a means of ensuring that sulfide in the parasite is maintained at a low level. T. vaginalis appears to lack serine acetyltransferase, the source of O-acetylserine in many cells, but has a functional 3-phosphoglycerate dehydrogenase and an O-phosphoserine aminotransferase that together result in the production of O-phosphoserine, suggesting that this is the physiological substrate. TvCS1 can also use thiosulfate as substrate. Overall, TvCS1 has substrate specificities similar to those reported for cysteine synthases of Aeropyrum pernix and Escherichia coli, and this is reflected by sequence similarities around the active site. We suggest that these enzymes are classified together as type B cysteine synthases, and we hypothesize that the use of O-phosphoserine is a common characteristic of these cysteine synthases. The level of cysteine synthase in T. vaginalis is regulated according to need, such that parasites growing in an environment rich in cysteine have low activity, whereas exposure to propargylglycine results in elevated cysteine synthase activity. Humans lack cysteine synthase; therefore, this parasite enzyme could be an exploitable drug target.
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PMID:Cysteine biosynthesis in Trichomonas vaginalis involves cysteine synthase utilizing O-phosphoserine. 1673 16