Reconstitution of Succinate-Coenzyme Q Reductase (Complex II) and Succinate Oxidase Activities by a Highly Purified, Reactivated Succinate Dehydrogenase

Abstract

Abstract Succinate dehydrogenase has been isolated in a highly purified form from succinate-coenzyme Q reductase preparations. The enzyme contains 1 mole of covalently bound flavin, 8 g atoms of iron, and 8 moles of acid-labile sulfide per 150,000 g of protein. It catalyzes succinate oxidation in the presence of phenazine methosulfate as electron acceptor at a rate of 26 to 32 µmoles per min x mg of protein (Vpmsmax ≃ 37). The succinate dehydrogenase thus prepared does not couple to the electron transport system, but it can be made to do so after treatment with Na2S, ferrous ions, and mercaptoethanol. Thus, both the succinate-coenzyme Q reductase and the succinoxidase systems have been reconstituted by combining the reactivated succinate dehydrogenase with appropriate segments of the respiratory chain. These results permit a better understanding of the composition and the electron transfer pathway of the mitochondrial respiratory chain from succinate to coenzyme Q.