Succinoxidase and Cytochrome Oxidase in Mitochondria from the Spadix ofArum

Abstract

1. Mitochondria prepared from young Arum spadix have enough cytochrome c oxidase to account for the rate at which succinate is oxidized, but succinoxidase activity increases markedly as the plants mature so that in old material cytochrome oxidase activity is only 10 per cent, of succinoxidase. 2. Disintegration of the mitochondria by vibration with ballotini, treatment with digitonin or incubation in the warm reveals an intra-mitochondrial cytochrome c oxidase probably active enough to account for the fastest rates of succinate oxidation. 3. Succinic dehydrogenase activity is demonstrated and experiments with p -chloromercuribenzoate indicate that it plays a part in the oxidation of succinate. 4. Cyanide completely inhibits both external and internal cytochrome oxidase but even at the earliest stages it only reduces succinoxidase by about 50 per cent. Antimycin A also inhibits succinoxidase by about 50 per cent.