Conversion of the Aminocrotonate Intermediate Limits the Rate of γ-Elimination Reaction Catalyzed by L-Cystathionine γ-lyase of the Yeast Saccharomyces cerevisiae

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概要

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• L-Cystathionine γ-lyase [EC 4. 4. 1. 1] of Saccharomyces cerevisiae was shown to bind cofactor pyridoxal 5'-phosphate, up to 2 molecules/subunit. The association constants of the enzyme for the cofactor were estimated to be 3.67×105M-1 and 9.05×103M-1. However, the latter value was too small for the binding to play a catalytic role. Changes in the absorption spectra of the enzyme in γ-elimination reaction mixtures with various amino acids as substrates were observed at 10°C to elucidate the reaction mechanism of the enzyme. The enzyme formed a chromophore exhibiting absorption at approximately 480 nm, which is characteristic of an aminocrotonate intermediate with O-succinyl-L-homoserine, L-cystathionine, L-homoserine, or O-acetyl-L-homoserine, at rates in this order. The intermediate was consumed at much lower rates than those of formation. The order of the rates of consumption was the same as the order of the formation rates and the order of the γ-elimination activity of the enzyme with the above-mentioned substrates. These results strongly suggested that the intermediate was essential for γ-elimination and that the reaction was rate-limited by its conversion into the product α-ketobutyrate. L-Cysteine sensitively inhibited the α, γ-elimination activity of the enzyme, and also retarded the formation of the chromophore when it was provided to the enzyme together with a substrate. The reason for these phenomena is discussed.

• 社団法人 日本生化学会の論文

著者

• Yamagata Shuzo

  Department Of Biotechnology Faculty Of Agriculture Gifu University

• IWAMA Tomonori

  Department of Biotechnology, Faculty of Agriculture, Gifu University

• Iwama Tomonori

  Department Of Biotechnology Faculty Of Agriculture Gifu University

• Okuda Yuriko

  Department Of Biotechnology Faculty Of Agriculture Gifu University

• Yasugahira Tomoko

  Department Of Biotechnology Faculty Of Agriculture Gifu University

関連論文

• Substrate Inhibition of L-Cysteine α,β-Elimination Reaction Catalyzed by L-Cystathionine γ-Lyase of Saccharomyces cerevisiae(Biochemistry & Molecular Biology)
• Comparative Characterization of the oah2 Gene Homologous to the oah1 of Thermus thermophilus HB8
• Conversion of the Aminocrotonate Intermediate Limits the Rate of γ-Elimination Reaction Catalyzed by L-Cystathionine γ-lyase of the Yeast Saccharomyces cerevisiae
• Determination of a Small Quantity of Cystine in the Presence of a Large Amount of Cysteine
• A MODIFICATION OF AN AMINO TERMINAL REGION OF THE SACCHAROMYCESCEREVISIAE MET17/MEET25 GENEPRODUCT
• Conversion of the Aminocrotonate Intermediate Limits the Rate of γ-Elimination Reaction Catalyzed by L-Cystathionine γ-lyase of the Yeast Saccharomyces cerevisiae

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