Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An activity stain to detect glutamine transaminase K subjected to nondenaturing polyacrylamide gel electrophoresis (ND-PAGE) was developed. The gel is incubated with a reaction mixture containing L-phenyl-alanine, alpha-keto-gamma-methiolbutyrate (alpha KMB), glutamate dehydrogenase, phenazine methosulfate (PMS) and nitroblue tetrazolium (NBT). Glutamine transaminase K catalyzes a transamination reaction between phenylalanine and alpha KMB. The resultant methionine is a substrate of glutamate dehydrogenase. The NADH formed in the oxidative deamination of methionine reacts with PMS and NBT to form a blue band on the surface of the gel coincident with glutamine transaminase K activity. Cysteine S-conjugate beta-lyase activity is detected in the gel by incubating the gel with a reaction mixture containing alpha KMB (to ensure maintenance of the enzyme in the pyridoxal 5'-phosphate form), S-(1,2-dichlorovinyl)-L-cysteine (DCVC), PMS, and NBT. The products of the lyase reaction interact with PMS and NBT to form a blue dye coincident with the lyase activity. In addition, a new assay procedure for measuring cysteine S-conjugate beta-lyase activity was devised. This procedure couples pyruvate formation from DCVC to the alanine dehydrogenase reaction. Preparations of purified rat kidney glutamine transaminase K yield a single protein band on ND-PAGE (apparent Mr approximately 95,000). This band coincides with both the cysteine S-conjugate beta-lyase and glutamine transaminase K activities. Activity staining showed that homogenates of rat kidney, liver, skeletal muscle, and heart possess a glutamine transaminase K/cysteine S-conjugate beta-lyase activity with an Rf value on ND-PAGE identical to that of purified rat kidney glutamine transaminase K.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glutamine transaminase K and cysteine S-conjugate beta-lyase activity stains. 172 51

Homocyst(e)ine, a normal metabolite, accumulates in certain inborn errors of sulfur amino acid metabolism. Since many amino acids are converted by enzymatic oxidation and by transamination to the corresponding alpha-keto acid analogs and related products, which may exert inhibitory effects on metabolism, and because the alpha-keto acid analog of homocysteine has not yet been prepared, the enzymatic oxidation of homocysteine was investigated with the aim of obtaining alpha-keto-gamma-mercaptobutyric acid. Oxidation of DL-homocysteine by L-amino acid oxidase led to formation of at least seven products that react with 2,4-dinitrophenylhydrazine; of these, five were identified: alpha-keto-gamma-mercaptobutyrate, the mono and diketo analogs of homolanthionine, and the mono and diketo analogs of homocystine. In addition, one product was tentatively identified as alpha-ketomercaptobutyric acid gamma-thiolactone. In the course of this work alpha-keto-gamma-mercaptobutyrate was found to be a substrate of lactate dehydrogenase. L-Homocysteine and its alpha-keto acid analog were shown to be substrates of glutamate dehydrogenase and kidney glutamine transaminase. DL-Homocysteine reacts readily with alpha-keto acids to form stable hemithioketals, which were found to be substrates of L- and D-amino acid oxidases. A scheme is presented which integrates some of the complexities involved in the oxidation metabolism of homocyst(e)ine. The significance of these findings is considered in relation to the toxicity of homocysteine, which accumulates in certain pathological states.
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PMID:Enzymatic oxidation of L-homocysteine. 286 Aug 73