The Oxidative Phosphorylation and ATPase Activity ofArumspadix Mitochondria in Relation to Heat Generation

Abstract

The respiration of Arum spadix mitochondria is coupled to a sub-maximal stoichiometry of ATP synthesis. The P/O ratios associated with the oxidation of succinate or malate are decreased by antimycin and increased by m-chlorobenzhydroxamic acid, an inhibitor of the alternative oxidase. The mitochondrial ATPase activity of 20–40 nmol (mg protein)⁻¹ min⁻¹ is independent of the maturity of the spadix and is unlikely to provide the mechanism for heat production during the odoriferous stage, which probably results from an increase in the rate of electron transport via the non-phosphorylating, cyanide-insensitive oxidase.