Solvent-derived protons in catalysis by brewers' yeast pyruvate decarboxylase.
Solvent-derived protons in catalysis by brewers' yeast pyruvate decarboxylase.
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啤酒酵母丙酮酸脱羧酶催化溶剂衍生的质子。
DOI：
10.1021/bi00043a006
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发表时间：
1995
期刊：
影响因子：
2.9
通讯作者：
Washabaugh,MW
中科院分区：
文献类型：
--
作者：
Harris,TK;Washabaugh,MW
1995年8月2日收到的修订版Mandarin pt摘要：丙酮酸脱羧酶同工酶（PDC; EC 4.1）对质子转移至二磷酸硫胺素（TDP）和2-（1-羟乙基）二磷酸硫胺素（HETDP）的催化作用。1.1)通过测定在非底物变构效应物异戊酰胺存在下丙酮酸生成乙醛反应的溶剂辨别氚同位素效应（kul fcT）圆盘，研究了来自卡尔氏酵母（Saccharomycescarlsbergensis）的异戊酰胺。TDP C（2）-L（pea = 0.98±0.06）和HETDP C（a）-L（c< a）= 1.01±0.07）（L=H或D）的分馏因子对所观察到的酶同位素区分没有显著贡献。在单转换条件下（[E]>[S]），TDP C（2）-L再质子化的（fo/foOdisc= 1.0）值与C（2）-通过与溶剂平衡的催化基团（0= 1）的氢转移一致。[1-L]在瞬态稳态（[E]<[S]）条件下乙醛的形成显示出在（kulkj）^= 0.39（单次转换）范围内增加的溶剂辨别氚同位素效应。
Revised Manuscript Received August 2, 1995s abstract: Catalysis of proton transfer to thiamin diphosphate (TDP) and 2-(l-hydroxyethyl) thiamin diphosphate (HETDP) by pyruvate decarboxylaseisozymes (PDC; EC 4.1. 1.1) from Saccharomyces carlsbergensis was investigated by determining the solvent discrimination tritium isotope effect,(kul fcT) disc, on the reaction of pyruvate to form acetaldehyde in the presence of the nonsubstrate allosteric effector pyruvamide. The fractionation factors for TDP C (2)-L ((pea,= 0.98±0.06) and HETDP C (a)-L ( c< a)= 1.01±0.07)(L=H or D) do not contributesignificantly to observed enzymic isotopic discrimination. The value of (fo/foOdisc= 1.0 for reprotonation of TDP C (2)-L under single-turnover conditions ([E]>[S]) is consistent with C (2)-hydrontransfer via a catalytic group (0= 1) equilibrated with solvent.[1-L] Acetaldehyde formation under transient steady-state ([E]<[S]) conditions shows solvent discrimination tritium isotope effects that increase over the range (kulkj)^= 0.39 (single turnover)