Kinetic and spectral parameters of interaction of Citrobacter freundii methionine γ-lyase with amino acids.
Kinetic and spectral parameters of interaction of Citrobacter freundii methionine γ-lyase with amino acids.
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弗氏柠檬酸杆菌蛋氨酸γ-裂解酶与氨基酸相互作用的动力学和光谱参数。
DOI：
10.1134/s0006297910100093
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Demidkina,TV
中科院分区：
文献类型：
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作者：
Morozova,EA;Bazhulina,NP;Anufrieva,NV;Mamaeva,DV;Tkachev,YV;Streltsov,SA;Timofeev,VP;Faleev,NG;Demidkina,TV
测定了弗氏柠檬酸杆菌蛋氨酸γ-裂解酶γ-消除反应中的底物以及不同结构的氨基酸对L-蛋氨酸γ-消除反应中酶的抑制作用。数据表明硫原子和亚甲基对底物和抑制剂的结合效率有重要贡献。测定了酶催化 C-α-和 C-β-质子与氘交换的速率常数，以及抑制剂 C-α-位氘标记对其 β-质子交换速率的动力学同位素效应。既没有发现β-质子交换的立体选择性，也没有发现α-同位素对β-质子交换率的明显影响。测定了甲硫氨酸γ-裂解酶的外部席夫碱的离子和互变异构组成。测定了与底物和抑制剂的配合物的光谱特征（吸收和圆二色光谱）。光谱和动力学数据表明氨基巴豆酸酯的脱氨基作用应该是酶促反应的速率决定阶段。
Kinetic parameters ofCitrobacter freundiimethionine γ-lyase were determined with substrates in γ-elimination reactions as well as the inhibition of the enzyme in the γ-elimination of L-methionine by amino acids with different structure. The data indicate an important contribution of the sulfur atom and methylene groups to the efficiency of binding of substrates and inhibitors. The rate constants of the enzyme-catalyzed exchange of C-α- and C-β-protons with deuterium were determined, as well as the kinetic isotope effect of the deuterium label in the C-α-position of inhibitors on the rate of exchange of their β-protons. Neither stereoselectivity in the β-proton exchange nor noticeable α-isotope effect on the exchange rates of β-protons was found. The ionic and tautomeric composition of the external Schiff base of methionine γ-lyase was determined. Spectral characteristics (absorption and circular dichroism spectra) of complexes with substrates and inhibitors were determined. The spectral and kinetic data indicate that deamination of aminocrotonate should be the ratedetermining stage of the enzymatic reaction.