Superoxide production and electron transport in mitochondrial oxidation of dihydroorotic acid

作者：Henry Jay Forman, James A. Kennedy · 发表于：Journal of Biological Chemistry · 年份：1975 · DOI：10.1016/s0021-9258(19)41421-x · 被引用次数：115 · 研究领域：Neonatal Health and Biochemistry、Metabolism and Genetic Disorders、Mitochondrial Function and Pathology

Production of superoxide radical during oxidation of dihydroorotate in rat liver mitochondria was not affected by antimycin A, thenoyltrifluoroacetone, or added ubiquinone but was inhibited by orotate, a product inhibitor of dihydroorotate dehydrogenase. It appears likely that superoxide is generated at the primary dehydrogenase. Dihydroorotate dehydrogenase differs from succinate dehydrogenase both in its utilization of ubiquinone and in the mechanism of cytochrome b reduction. Thenoyltrifluoroacetone completely inhibits fumarate synthesis and reduction of cytochrome b by succinate. Formation of orotate is only partially inhibited by thenolytrifluoroacetone and the inhibitor does not prevent reduction of cytochrome b by dihydroorotate. It is proposed that several pathways exist for linkage of the primary dihydrorotate dehydrogenase with the electron transport chain. One route involves electron transfer from ubiquinone to cytochrome c and is inhibited by thenoyltrifluoroacetone. A second route bypasses ubiquinone and is inhibited by antimycin A. A third pathway utilizes both ubiquinone and cytochrome b and is partiayly inhibited by either thenoyltrifluoroacetone or antimycin A.