Department of Plant and Microbial Biology, University of Minnesota, Twin Cities, Saint Paul, MN, 55108, USA.
Department of Horticultural Science, University of Minnesota, Twin Cities, Saint Paul, MN, 55108, USA.
Nat Commun. 2024 Jan 29;15(1):846. doi: 10.1038/s41467-024-45134-0.
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.
琥珀酸脱氢酶的一个常见副反应将苹果酸氧化为烯醇式草酰乙酸（OAA），这是 OAA 的一种代谢失活形式，是琥珀酸脱氢酶的强抑制剂。我们从牛心线粒体中纯化了一种具有 OAA 互变异构酶（OAT）活性的酶（OAT1），它将烯醇-OAA 转化为生理酮式-OAA 形式，并确定它属于高度保守且以前未被表征的富马酰乙酰乙酸水解酶结构域包含蛋白家族。从所有三个生命领域表达的异源蛋白都具有很强的 OAT 活性，并且敲除 OAT1 同源物会导致明显的生长缺陷。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，并且敲除 OAT1 会导致与无氧呼吸相关的乙酸和其他代谢物的显著增加。在体外实验中，OAT1 在生理浓度的琥珀酸和苹果酸存在下，将琥珀酸脱氢酶反应速率提高了 35%。我们的结果表明，OAT1 是一种普遍的代谢物修复酶，通过防止琥珀酸脱氢酶抑制来提高有氧呼吸效率。
