Oxidation through the cytochrome system of substituted phenylenediamines

Abstract

The oxidation through the cytochrome system (heart-muscle cytochrome oxidase prepn.) of quinol, p-aminophenol, p-phenylenediamine, and mono-, di-, and tetra-methyl-substituted p-phenylenediamines, is decreasingly dependent on added cytochrome c in the order given. For the most complex reductants the endogenous cytochrome c of the oxidase prepn. is in itself sufficient for a max. oxidation rate. If the endogenous cytochrome c of the oxidase is inactivated by low-temp. treatment, externally added cytochrome c can augment the oxidation of all reductants. Cytochrome c is always a part of the carrier chain; in no case does the oxidase act directly on the reductant. The dimethyl-, tetramethyl-, and diethyl-substituted p-phenylenediamines form oxidation products which are toxic for the oxidase. The significance of the oxidation-reduction potential of the various members of the reductant series was considered. The implication of the participation of cytochrome c in the oxidation of dimethyl-p-phenylene-diamine is discussed for respiration expts. on fertilized and unfertilized sea-urchin eggs. The suggestion that cytochrome c is invariably a part of the echinoderm oxidase system is very strongly supported.