Johanson R A, Reeves H C
Biochim Biophys Acta. 1977 Jul 8;483(1):24-34. doi: 10.1016/0005-2744(77)90004-3.
Oxalacetate and glyoxylate are each weak inhibitors of NADP+-specific isocitrate dehydrogenase (threo-DS-isocitrate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.42)9 Together, however, they act in a concerted manner and strongly inhibit the enzyme. The rates of formation and dissociation of the enzyme inhibitor complex, and the rate of formation and the stability of the aldol condensation product of oxalacetate and glyoxylate, oxalomalate, were examined. The data obtained do not support the often suggested possibility that oxalomalate, per se, formed non-enzymatically in isocitrate dehydrogenase assay mixtures containing oxalacetate and glyoxylate, is responsible for the observed inhibition of the enzyme. Rather, the data presented in this communication suggest that oxalacetate binds to the enzyme first, and that the subsequent binding of glyoxylate leads to the formation of a catalytically inactive enzyme-inhibitor complex.
草酰乙酸和乙醛酸分别是NADP⁺特异性异柠檬酸脱氢酶（苏式-DS-异柠檬酸：NADP⁺氧化还原酶（脱羧），EC 1.1.1.42）的弱抑制剂。然而，它们共同作用时，会协同发挥作用并强烈抑制该酶。研究了酶抑制剂复合物的形成和解离速率，以及草酰乙酸和乙醛酸的醛醇缩合产物草酰苹果酸的形成速率和稳定性。所获得的数据并不支持常被提及的一种可能性，即在含有草酰乙酸和乙醛酸 的异柠檬酸脱氢酶测定混合物中通过非酶方式形成的草酰苹果酸本身是观察到的酶抑制作用的原因。相反，本通讯中呈现的数据表明，草酰乙酸首先与酶结合，随后乙醛酸的结合导致形成无催化活性的酶-抑制剂复合物。
