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)

Serine dehydratase (L-serine hydro-lyase, EC 4.2.1.13) WAS DEMONSTRATED IN LIVER TISSUE OF RATS BY AN INdirect immunofluorescent method. In the adult rat liver, serine dehydratase was localized to periportal hepatocytes, diffusely in their cytoplasm. The enzyme-specific fluorescence was absent or extremely low in the centrolobular hepatocytes. It was not demonstrated in nonparenchymal cells. Feeding a 90% protein diet for 5 days caused marked induction of this enzyme in the periportal and midzonal hepatocytes but no induction in the centrolobular hepatocytes. In the newborn rat liver, there was no apparent intralobular heterogeneity seen in the distribution of serine dehydratase, either before or after dietary induction. After 1 week of age, there was a gradual development of the intralobular hetero-geneity of the enzyme, which was emphasized by dietary stimulation. A comparative study of the induction pattern between the livers of intact and adrenalectomized rats suggested that there is no heterogeneity among serine-dehydratase-positive cells with respect to hormonal regulation of this enzyme by either glucagon or cortisone.
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PMID:Immunohistochemical demonstration of serine dehydratase in rat liver. 16 93

Tryptophan synthase from Escherichia coli (L-serine hydro-lyase (adding indole), EC 4.2.1.20) synthesizes L-trypotophan from indoleglycerol phosphate and L-serine, releasing glyceraldehyde 3-phosphate, or from indole and L-serine. The latter reaction (B reaction), catalyzed either by the beta2 species or by the (alpha2 beta2) complex, has been studied by steady-state methods. A sequential mechanism is indicated. Inhibition experiments with the substrate analogue benzimidazole were carried out in order to distinguish between random and ordered mechanisms. The results are compatible with a random sequential mechanism. The dissociation constants of the enzyme-substrate complexes are evaluated. When catalyzed by the tetrameric complex (alpha2 beta2) the B reaction is inhibited by higher concentrations of the substrate indole. This inhibition does not follow the usual substrate inhibition pattern. The question whether the binding of indole to the alpha-subunit exerts an inhibitory effect on the beta2 species, possibly by reversing the activation by the alpha subunit of the beta2 species, is discussed.
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PMID:On the mechanism of action of Escherichia coli tryptophan synthase. Steady-state investigations. 34 87

Cystathionine beta-synthase has been purified from human liver more than 3000-fold by a series of steps including high speed centrifugation, ammonium sulfate fractionation, chromatography on hydroxylapatite and DEAE-cellulose, gel filtration, preparative polyacrylamide gel electrophoresis, and glycerol density gradient centrifugation. The enzyme obtained is homogeneous as judged by polyacrylamide gel electrophoresis in four different systems: native, isoelectric focusing, in sodium dodecyl sulfate, and in 8 M urea. The native enzyme has an estimated molecular weight of 94,000 and is composed of two apparently identical subunits of 48,000. The pure enzyme has a specific activity of 160 units/mg of protein and contains tightly bound cofactor, pyridoxal 5' -phosphate. It is possesses serine sulfhydrase as well as cystathionine synthase activity. It has a broad pH optimum from 8.4 to 9.0, apparent Km values for L-serine of 1.15 mM and for L-homocysteine of 0.59 mM, and a pI of 5.2 The enzyme is stable over a pH range from 6.5 to 8.0 in phosphate buffers and can be stored in 40% glycerol at -15 degrees C for at least 1 month.
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PMID:Purification and properties of cystathionine beta-synthase from human liver. Evidence for identical subunits. 68 63

1. Methionine adenosyltransferase (ATP:L-methionine-S-adenosyl transferase, EC 2.5.1.6), cystathionine beta-synthase F1L-serine hydro-lyase (adding homocysteine), EC 4.2.1.22] and cystathionine gamma-lyase [L-cystathionine cysteine-lyase (deaminating), EC 4.4.1.1] activities were found only in the cytosol fraction of rat liver cells. None was found in the mitochondrial or endoplasmic reticulum fractions as judged by the distribution of marker enzymes on a density gradient after centrifugation of the cytoplasmic fraction of a liver homogenate, or in a preparation of liver cell nuclei. 2. Polymorphs, lymphocytes (with admixed monocytes) and mixed bone marrow white cells contained no methionine adenosyl transferase, cystathionine beta-synthase or cystathionine gamma-lyase activities. 3. The possible bearing of these results on the problem of abnormal cystine storage in cystinosis is briefly discussed.
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PMID:Methionine adenosyltransferase, cystathionine beta-synthase and cystathionine gamma-lyase activity of rat liver subcellular particles, human blood cells and mixed white cells from rat bone marrow. 105 81

Characterization of the physical and catalytic properties of the enzyme responsible for nematode "activated L-serine sulfhydrase" activity (L-cysteine + R-SH-->cysteine thioether + H2S) has led to its identification as a novel, variant form (allelozyme) of cystathionine beta-synthase that is distinct from a mammalian-type synthase also present in nematodes. Additional work has demonstrated the ability of live Panagrellus redivivus to produce H2[35S] from exogenous L-[35S]cysteine and 2-mercaptoethanol, thus providing preliminary evidence for the in vivo operation of the activated L-serine sulfhydrase reaction in nematodes.
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PMID:The identification of a variant form of cystathionine beta-synthase in nematodes. 149 73

Addition of serum, obtained from patients suffering from an acute psychosis characterized by dysperceptions, to the culture media of fibroblasts altered the amino acid metabolism in these cells. After subculturing of fibroblasts in the presence of serum obtained from these patients, the concentrations of both serine and methionine were decreased in the medium as well as in the fibroblasts. Moreover, the concentration of taurine in the fibroblasts was increased. The specific activities of serine hydroxymethyltransferase and cystathionine beta-synthase were also measured in the fibroblasts. It was found that both enzyme activities were significantly higher after subculturing with patients' serum as compared with serum obtained from healthy controls. It is concluded that a factor, present in the serum of these acute psychotic patients, is responsible for the observed changes in serine, taurine, and methionine concentrations in the fibroblasts as well as for the increased enzyme activities mentioned.
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PMID:Changes in serine metabolism by a serum factor present in a group of episodic psychotic patients. 175 1

Eight classes of pyridoxal 5'-phosphate dependent enzymes have been investigated in Nippostrongylus brasiliensis in parallel with rat tissues. The range of decarboxylases detected in N. brasiliensis was limited in comparison with rat tissues. N. brasiliensis possessed a highly active L-serine hydroxymethyltransferase, but in contrast with rat liver, 5-aminolevulinic acid synthetase was absent. Similar levels of L-serine and L-threonine dehydratase activities were detected in N. brasiliensis and rat liver, and both organisms lacked L-alanine racemase, L-tryptophan synthetase and L-methionine gamma-lyase. The demonstration of cystathionine beta-synthase and gamma-cystathionase in N. brasiliensis suggests the presence of a functional trans-sulphuration sequence. The substrate specificities of the nematode cystathionine beta-synthase and gamma-cystathionase varied significantly from those of the corresponding mammalian enzymes. Particularly striking was the ability of N. brasiliensis cystathionine beta-synthase to catalyse the non-mammalian 'activated L-serine sulphydrase' reaction (L-cysteine + R-SH----cysteine thioether + H2S). N. brasiliensis and rat liver exhibited comparable abilities to transaminate amino acids via the 2-oxoglutarate: glutamate system.
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PMID:Pyridoxal 5'-phosphate dependent enzymes in the nematode Nippostrongylus brasiliensis. 175 92

The activities of gamma-cystathionase and cystathionine beta-synthase were investigated in a range of gastrointestinal, free-living and entomophagous nematodes. Although nematode gamma-cystathionase used the same range of substrates as the mammalian hepatic enzyme, its activity was extremely low and there were significant interspecies variations with respect to the relative order of active substrates. Like the mammalian liver enzyme, nematode cystathionine beta-synthase showed activity in the directions of both cystathionine synthesis and the forward and reverse "L-serine sulphhydrase" reactions. However, the most important feature of the survey was the widespread ability of nematode cystathionine beta-synthase to catalyse the non-mammalian "activated L-serine sulphhydrase" reaction (L-cysteine + R-SH----cysteine thioether + H2S). Additional survey work revealed that the ability to catalyse the activated L-serine sulphhydrase reaction was almost universal amongst nematodes. Activated L-serine sulphhydrase activity was also demonstrated in the acanthocephalan Pomphorhynchus laevis but was absent from cestodes and digeneans.
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PMID:Cystathionine beta-synthase and gamma-cystathionase in helminths. 180 16

To assess the extent to which low hepatic gamma-cystathionase levels affect methionine flux to cysteine in hepatocytes, the effect of inhibition of gamma-cystathionase activity with propargylglycine on the metabolism of L-[35S]methionine was determined in studies with freshly isolated rat hepatocytes. gamma-Cystathionase activity was inhibited 25%, 42%, 63% and 76% (maximal inhibition) by treatment with 2.5 mumol/L, 0.01 mmol/L, 0.02 mmol/L and 2 mmol/l propargylglycine, respectively. Inhibition of gamma-cystathionase activity with up to 0.02 mmol/L propargylglycine had no statistically significant effect on [35S]glutathione, [35S]sulfate or [35S]cysteine formation from [35S]methionine. However, treatment of cells with 2 mmol/L propargylglycine markedly inhibited the metabolism of [35S]methionine to [35S]glutathione by 93%, to [35S]sulfate by 88% and to [35S]cysteine by 89%; [35S]cystathionine accumulation in these incubation systems was 60 times control. Hepatic gamma-cystathionase activity in premature infants has been reported to be about 23% of mature levels (Zlotkin and Anderson, 1982; Pediatr. Res. 16: 65-68); this level of gamma-cystathionase activity may limit cysteine synthesis by the methionine transsulfuration pathway. No evidence for cysteine synthesis from serine and sulfide, which can be catalyzed by cystathionine beta-synthase, or for methionine metabolism by an S-adenosylmethionine-independent pathway was obtained.
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PMID:Role of the transsulfuration pathway and of gamma-cystathionase activity in the formation of cysteine and sulfate from methionine in rat hepatocytes. 211 6

A disturbance of serine-glycine metabolism in a group of patients who became psychotic after oral intake of serine may be due to any serine-related enzyme abnormality. In order to elucidate this problem, we studied several enzymes in fibroblasts obtained from these patients. First, the enzyme serine hydroxymethyltransferase was investigated. The apparent Km values for serine, L-tetrahydrofolate (H4folate), and pyridoxal 5'-phosphate, as well as the maximal velocities of the forward and backward reactions measured in fibroblasts obtained from patients, were not different from those in the cells from controls. We also measured the activities of another three enzymes of the folic acid cycle, viz., 5,10-methylene-H4folate dehydrogenase, 10-formyl-H4folate synthetase, and 5,10-methenyl-H4folate cyclohydrolase, as well as the enzyme cystathionine beta-synthase. Again, no differences were found among these enzymes in fibroblasts from patients and controls. It can be concluded that the psychotic symptoms occurring after the administration of serine are not the result of any malfunctioning of the enzymes investigated.
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PMID:Serine and folate metabolism in fibroblasts from episodic psychotic patients with psychedelic symptoms. 309 Oct 98


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