[牛肾上腺丙酮酸脱氢酶复合体催化反应的稳态动力学]

[Steady-state kinetics of the bovine adrenal pyruvate dehydrogenase complex-catalyzed reactions].

作者信息

Strumilo S A, Senkevich S B, Vinogradov V V

出版信息

Biokhimiia. 1980 Aug;45(8):1365-70.

Abstract

The hyperbolic dependence of the initial rate of the adrenal pyruvate dehydrogenase complex-catalyzed reactions on pyruvate, CoA and NAD concentrations was established. The Lineweaver--Burk plots of v0 against one substrate concentration at constant unsaturating concentrations of other substrates represent families of parallel lines. The Km values for pyruvate, CoA and NAD are 0,017, 0.005 and 0.030 mM, respectively. CoA-SAc was shown to compete with CoA (Ki=0.067 mM) whereas NADH--with NAD (Ki=0.023 mM). Both CoA-SAc and NADH are uncompetitive inhibitors with respect to pyruvate. The inhibition of CoA-SAc against NAD is of a mixed type, while that of NAD against CoA is non-competitive. The results obtained are in agreement with the kinetic model of a three-site "ping-pong" mechanism.

摘要

已确定肾上腺丙酮酸脱氢酶复合体催化反应的初始速率对丙酮酸、辅酶A和烟酰胺腺嘌呤二核苷酸（NAD）浓度呈双曲线依赖性。在其他底物恒定不饱和浓度下，以初始速率v0对一种底物浓度绘制的林-贝氏（Lineweaver--Burk）图代表了平行直线族。丙酮酸、辅酶A和NAD的米氏常数（Km值）分别为0.017毫摩尔、0.005毫摩尔和0.030毫摩尔。已表明乙酰辅酶A（CoA-SAc）与辅酶A竞争（抑制常数Ki = 0.067毫摩尔），而还原型烟酰胺腺嘌呤二核苷酸（NADH）与烟酰胺腺嘌呤二核苷酸（NAD）竞争（抑制常数Ki = 0.023毫摩尔）。CoA-SAc和NADH对丙酮酸均为反竞争性抑制剂。CoA-SAc对NAD的抑制作用为混合型，而NAD对辅酶A的抑制作用为非竞争性。所得结果与三位点“乒乓”机制的动力学模型一致。