Gomazkova V S, Krasovskaia O E
Biokhimiia. 1979 Jun;44(6):1126-36.
The activity of alpha-ketoglutarate dehydrogenase complex from pigeon breast muscle is controlled by ADP and the reaction products, i. e. succinyl-CoA and NADH. ADP activates the alpha-ketoglutarate dehydrogenase component of the complex, whereas NADH inhibits alpha-ketoglutarate dehydrogenase and lipoyl dehydrogenase. In the presence of NADH the kinetic curve of the complex with respect to alpha-ketoglutarate and NAD and the dependence of upsilon versus [NAD] and upsilon versus [Lip (SH)2] in the lipoyl dehydrogenase reaction are S-shaped. In the absence of inhibitor ADP had no activating effect on lipoyl dehydrogenase; however, in the presence of NADH ADP decreases the cooperativity for NAD. The cooperative kinetics of the constituent enzymes of the complex are indicative of its allosteric properties. Isolation of the alpha-ketoglutarate dehydrogenase complex and its lipoyl dehydrogenase and alpha-ketoglutarate dehydrogenase components in a desensitized state confirms their allosteric nature. It is assumed that NADH effects of isolated alpha-ketoglutarate dehydrogenase is due to a shift in the equilibrium between different oligomeric forms of the enzyme.
鸽胸肌中α-酮戊二酸脱氢酶复合体的活性受二磷酸腺苷(ADP)以及反应产物即琥珀酰辅酶A和还原型辅酶I(NADH)的调控。ADP激活该复合体中的α-酮戊二酸脱氢酶组分,而NADH则抑制α-酮戊二酸脱氢酶和硫辛酰胺脱氢酶。在有NADH存在的情况下,该复合体相对于α-酮戊二酸和烟酰胺腺嘌呤二核苷酸(NAD)的动力学曲线,以及硫辛酰胺脱氢酶反应中反应速率(υ)与[NAD]和υ与[二氢硫辛酸(Lip(SH)₂)]的关系曲线均呈S形。在没有抑制剂的情况下,ADP对硫辛酰胺脱氢酶没有激活作用;然而,在有NADH存在时,ADP会降低对NAD的协同效应。该复合体中各组成酶的协同动力学表明了其别构性质。分离出脱敏状态下的α-酮戊二酸脱氢酶复合体及其硫辛酰胺脱氢酶和α-酮戊二酸脱氢酶组分,证实了它们的别构性质。据推测,分离出的α-酮戊二酸脱氢酶受NADH影响是由于该酶不同寡聚形式之间平衡的改变。