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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)

The relationship between enzyme activity, cell geometry, and the ploidy levels has been investigated in Saccharomyces cerevisiae. Diploid cells have 1.57 times the volume of haploid cells under nonlimiting growth conditions (minimal medium). However, when diploid cells are grown under conditions of carbon limitation, they have the same volume as haploid cells. Thus, by altering the environmental conditions, cell size can be varied independently of the degree of ploidy. The results indicate that the basic biochemical parameters of the cell are primarily determined by cell geometry rather than ploidy level. RNA content, protein content, and ornithine transcarbamylase (carbamoylphosphate: L-ornithine carbamoyltransferase, EC 2.1.3.3), tryptophan synthetase [L-serine hydro-lyase (adding indole), EC 4.2.1.20], and invertase (alpha-D-glucoside glucohydrolase, Ec 3.2.1.20) activity are related to cell volume, whereas acid phosphatase (orthophosphoric-monoester phosphohydrolase, EC 3.1.3.2) activity, a cell surface enzyme, is related to the surface area of the cells. Fitness is determined by the activity of certain cell surface enzymes, such as acid phosphatase, diploids would be expected to have a lower fitness than haploids because of the lower surface area/volume ratio. However, when fitness is determined by the activity of an internal enzyme, diploids would be expected to have the same fitness as haploids. Results from competition experiments between haploids and diploids are consistent with these predictions. The significance of these results to the evolution of diploidy as the predominant phase of the life cycle of higher plants and animals is discussed.
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PMID:The relationship between enzyme activity, cell geometry, and fitness in Saccharomyces cerevisiae. 109 69

We have developed conditions for efficient cDNA cloning of nanogram amounts of purified mRNAs coding for cystathionine beta-synthase [L-serine hydro-lyase (adding homocysteine), EC 4.2.1.22] and for the cytosolic precursors of mitochondrial ornithine transcarbamylase (carbamoylphosphate:L-ornithine carbamoyltransferase, EC 2.1.3.3) and the beta subunit of propionyl-CoA carboxylase [propanoyl-CoA: carbon-dioxide ligase (ADP-forming), EC 6.4.1.3]. The three mRNAs, prepared by sequential immunoselection from the same batch of rat liver polysomes, were pooled (20 ng each), and cDNA was synthesized by using avian reverse transcriptase. The second DNA strand was prepared by "nick-translation repair" of the cDNA . mRNA hybrid with RNase H, polymerase I, and DNA ligase from Escherichia coli. The double-stranded (ds) DNA was tailed with deoxycytidine residues, annealed with Pst I-cut/dG-tailed pBR322, and used to transform E. coli. The library generated by this three-step procedure contained 5000 independent colonies. A 550-base-pair (bp) cDNA clone of the beta subunit of propionyl-CoA carboxylase was detected by hybrid-selected translation; it was then used to screen the library for longer cDNAs. Two hybridizing cDNAs, 1200 and 1000 bp long with a 200-bp overlap, representing together a full-length copy of the coding region and 446 bp of 3' untranslated sequence, were recovered. Each plasmid mapped to the region q13.3----q22 of human chromosome 3. Cystathionine beta-synthase clones were obtained by screening the library with a single-stranded [32P]cDNA prepared directly from the highly purified synthase mRNA by reverse transcriptase. The longest hybridizing cDNA of 1700 bp was used in hybrid-selected translation and detected a polypeptide of 63 kDa, identical in size to rat liver synthase. In situ hybridization of this cDNA to q22 of human chromosome 21 confirmed two previous tentative assignments of the synthase locus to this chromosome.
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PMID:Cloning and screening with nanogram amounts of immunopurified mRNAs: cDNA cloning and chromosomal mapping of cystathionine beta-synthase and the beta subunit of propionyl-CoA carboxylase. 345 73

Bubonic plague is transmitted by fleas whose feeding is blocked by a Yersinia pestis biofilm in the digestive tract. Y. pestis also block feeding of Caenorhabditis elegans by forming a biofilm on the nematode head, making the nematode an experimentally tractable surrogate for fleas to study plague transmission. Arabinose 5-phosphate isomerase (API), encoded by Y. pestis yrbH, catalyses the conversion of ribulose 5-phosphate into arabinose 5-phosphate (A5P), the first committed step in the 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) biosynthesis pathway. Here we show that Y. pestis YrbH is a multifunctional protein required for both Kdo biosynthesis and biofilm formation on C. elegans. The YrbH protein contains four functional components: biofilm-related region 1 (B1), a sugar isomerase domain (SIS), biofilm-related region 2 (B2) and a cystathionine beta-synthase domain pair (CBS). B1, SIS and B2 are all required for API function, but any of the three is sufficient for a biofilm-related function. The CBS domain appears to negatively regulate the biofilm-related function.
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PMID:Yersinia pestis YrbH is a multifunctional protein required for both 3-deoxy-D-manno-oct-2-ulosonic acid biosynthesis and biofilm formation. 1681 7