Maleylacetone cis-trans-isomerase. Mechanism of the interaction of coenzyme glutathione and substrate maleylacetone in the presence and absence of enzyme
作者:Stanley Seltzer、Mow Lin
DOI:10.1021/ja00505a042
日期:1979.5
enzyme-catalyzed cis-trans isomerization. In the absence of enzyme, reaction of the coenzyme with maleylacetone or its trans isomer, fumarylacetone, has been found to lead to an adduct, S-2-(4,6-dioxoheptanoic acid)glutathione. The same diastereomer of the adduct is formed from either geometric isomer, suggesting that the reaction of GSH with maleylacetone proceeds by a slow catalyzed cis-trans isomerization followed
以前对马来酰丙酮顺反异构酶的研究表明,辅酶谷胱甘肽 (GSH) 可能在酶催化的顺反异构化中充当亲核试剂。在没有酶的情况下,辅酶与马来酰丙酮或其反式异构体富马酰丙酮的反应被发现会产生加合物 S-2-(4,6-二氧庚酸)谷胱甘肽。加合物的相同非对映异构体由任一几何异构体形成,这表明 GSH 与马来酰丙酮的反应通过缓慢催化的顺反异构化进行,然后是 GSH 缀合物加成到反式异构体的快速反应。这种机制通过同位素稀释实验和动力学方法得到证实,该方法涉及将分数当量的 GSH 重复添加到马来丙酮溶液中。在 GSH 催化的顺反异构化过程中形成的中间体被认为是硫在 C-2 处形成的二烯二醇,并且该中间体在 C-3 处发生质子化之前经历键旋转和消除。通过类比和其他证据,建议酶-辅酶-底物反应具有类似的机制和中间体。2个数字,4个表格。