Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: K02A6 .4
 471,332 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. An S-alkyl-L-cysteine lyase (EC 4.4.1.6) was purified to apparent homogeneity from extracts of acetone-dried powders of the hypocotyls of etiolated 5-day-old seedlings of Acacia farnesiana Willd. 2. The enzyme catalyses a beta-elimination reaction and will utilize both the thioether and sulphoxide form of the substrate. 3. There is a braod specificity with regard to the alkyl substituent, but cystathionine is utilized very poorly. 4. The pH optimum is 7.8 and the Km value for the probable natural substrate L-djenkolate is 0.3 mM. 5. Both sodium dodecyl sulphate-polyacrylamide-gel electrophoresis and ultracentirfugal analysis give a molecular weight of about 144000. 6. One mol of pyridoxal phosphate is bound/mol of enzyme. 7. The energy of activation with L-djenkolate as the substrate is 53.1 kJ/mol. 8. The enzyme has a partial specific volume of 0.56 and S20,w 7.26S.
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PMID:Purification and properties of S-alkyl-L-cysteine lyase from seedlings of Acacia farnesiana Willd. 24 29

S-Alkylcysteine alpha, beta-lyase [EC 4.4.1.6] of Pseudomonas putida catalyzes alpha,beta-elimination of L-djenkolate [3,3'-methylenedithiobis(2-aminopropionic acid)] to produce pyruvate, ammonia, and S-(mercaptomethyl)cysteine initially. Secondly, S-(mercaptomethyl)-cysteine, which was identified in the form of S-(mercaptomethyl)cysteine thiolactone and S-(2-thia-3-carboxypropyl)cysteine in the absence and presence of iodoacetic acid, respectively, is decomposed enzymatically to pyruvate, ammonia, and bis(mercapto)methane, or spontaneously to cysteine, formaldehyde, and hydrogen sulfide. Balance studies showed that 1.3 mol each of pyruvate and ammonia and 0.2 mol each of formaldehyde and cysteine were produced with consumption of 1 mol of L-djenkolate. 1,2,4,5-Tetrathiane, 1,2,4-trithiolane, 1,2,4,6-tetrathiepane, and 1,2,3,5,6-pentathiepane, which are derivatives of bis(mercapto)methane, were also produced during the alpha,beta-elimination of L-djenkolate. In addition, a polymer with the general formula of -(CH2S)n- was produced as a white precipitate. When the alpha,beta-elimination of L-djenkolate was carried out in the presence of 20 mM iodoacetic acid, neither formaldehyde, cysteine, hydrogen sulfide, or the polymer were formed. Instead, the S-carboxymethyl derivatives of bis(mercapto)methane and S-(mercaptomethyl)cysteine were produced in addition to pyruvate and ammonia.
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PMID:Degradation of L-djenkolate catalyzed by S-alkylcysteine alpha,beta-lyase from Pseudomonas putida. 186 19

S-Alkylcysteine alpha,beta-lyase [EC 4.4.1.6] was purified to more than 90% homogeneity from the cell extract of Pseudomonas putida ICR 3640. The enzyme has a molecular weight of about 195,000, and is composed of six subunits identical in molecular weight (37,000). Pyridoxal 5'-phosphate is required as a cofactor. The enzyme catalyzes the alpha,beta-elimination of S-methyl-L-cysteine and its analogs such as S-ethyl-L-cysteine, L-djenkolate, Se-methyl-DL-selenocysteine, and O-methyl-L-serine. However, S-methyl-D-cysteine, L-methionine, and L-norvaline were inert. The enzyme catalyzes also the beta-replacement reaction of the thiomethyl group of S-methyl-L-cysteine with various thiols to yield the corresponding S-substituted cysteines. In addition to S-methyl-L-cysteine, Se-methyl-DL-selenocysteine and O-methyl-L-serine also serve as substrates in the beta-replacement reaction.
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PMID:Purification and characterization of S-alkylcysteine alpha,beta-lyase from Pseudomonas putida. 208 76

1. Rat liver cystathionase [EC.4.4.1.1] mediated a cleavage reaction of the C-S bond of S-alkyl-L-cysteine conjugates to give equimolar amounts of corresponding thiols, ammonia, and pyruvic acid. Neither S-aryl- nor S-aralkyl-L-cysteine conjugates were acceptable substrates. 2. The Km value for S-(tert-butyl)-L-cysteine was 0.3 mM at pH 8.5 in Tris-HCl buffer. 3. The S-alkyl-L-cysteine lyase activity of cystathionase was inhibited with carbonyl reagents and dithiothreitol. 4. The present finding that cystathionase has activity towards cysteine conjugates may provide some insights into the role of this enzyme in the metabolism of xenobiotics.
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PMID:Involvement of cystathionase in the formation of alkane-thiols from corresponding cysteine conjugates. 285 20