The action of inhibitors on the system of enzymes which catalyse the aerobic oxidation of succinate

Abstract

During storage of a particular heart-muscle prepn. at 4[degree] for several wks., the activity of the succinic oxidase system at first increased, then decreased, while the succinic dehydro-genase activity remained constant. It is believed that this was due to an alteration of the physical properties of the particles of the enzyme prepn. The concn. of the phosphate buffer had a profound effect on the activity of the succinic oxidase system, but had little action on the succinic dehydrogenase. The inhibitory action of low phosphate concns. was greater when the activity was measured without the addition of cytochrome c; it was completely prevented by denatured globin. The claim of Straub (Zeitschr. Physiol. Chem. 272: 219, 1942) to have removed, by the action of bile salts, a component of the succinic oxidase system, which was restored by the addition of a heart-muscle extract, heated under alkaline conditions, was not confirmed. Bile salts had a general physical effect on the particles of the enzyme prepn. A hemolytic substance had the same effect as bile salts on the system. Inhibition of the succinic oxidase system by nonspecific agents possessed certain characteristics, which distinguished this inhibition from that induced by agents which combined specifically with a component of the system.