PDF(Pubmed)
Abstract：
A prevalent side-reaction of succinate dehydrogenase oxidizes malate to enol-oxaloacetate (OAA), a metabolically inactive form of OAA that is a strong inhibitor of succinate dehydrogenase. We purified from cow heart mitochondria an enzyme (OAT1) with OAA tautomerase (OAT) activity that converts enol-OAA to the physiological keto-OAA form, and determined that it belongs to the highly conserved and previously uncharacterized Fumarylacetoacetate_hydrolase_domain-containing protein family. From all three domains of life, heterologously expressed proteins were shown to have strong OAT activity, and ablating the OAT1 homolog caused significant growth defects. In Escherichia coli, expression of succinate dehydrogenase was necessary for OAT1-associated growth defects to occur, and ablating OAT1 caused a significant increase in acetate and other metabolites associated with anaerobic respiration. OAT1 increased the succinate dehydrogenase reaction rate by 35% in in vitro assays with physiological concentrations of both succinate and malate. Our results suggest that OAT1 is a universal metabolite repair enzyme that is required to maximize aerobic respiration efficiency by preventing succinate dehydrogenase inhibition.
摘要：
琥珀酸脱氢酶的普遍副反应将苹果酸氧化为烯醇草酰乙酸（OAA），OAA的代谢失活形式，是琥珀酸脱氢酶的强抑制剂。我们从具有OAA互变异构酶（OAT）活性的牛心脏线粒体酶（OAT1）中纯化，该酶将烯醇-OAA转化为生理酮-OAA形式，并确定它属于高度保守且先前未表征的含乙酰乙酸磺酰基水解酶结构域的蛋白质家族。从生活的三个领域，异源表达的蛋白质被证明具有很强的OAT活性，和烧蚀OAT1同源物导致显著的生长缺陷。在大肠杆菌中，琥珀酸脱氢酶的表达对于OAT1相关的生长缺陷的发生是必要的，和消融OAT1导致乙酸盐和其他与厌氧呼吸相关的代谢物显着增加。在生理浓度的琥珀酸和苹果酸的体外测定中，OAT1使琥珀酸脱氢酶反应速率提高了35％。我们的结果表明，OAT1是一种通用的代谢修复酶，通过防止琥珀酸脱氢酶抑制来最大化有氧呼吸效率。
