Oxidation of NADH and NADPH by mitochondria from the yeast Candida utilis

Abstract

Mitochondria were isolated from Candida utilis CBS 621 grown in carbon-limited continuous cultures on glucose, gluconate, xylose, ethanol or acetate as the carbon source and ammonia or nitrate as the nitrogen source. In all cases mitochondria were isolated which could oxidize exogenous NADH and NADPH via a cyanide- and antimycin A-sensitive but rotenone-insensitive respiratory chain. Oxidation of NADH and NADPH was coupled to energy conservation as evidenced by high respiratory control values. Different respiratory control values of mitochondria with NADH and NADPH as well as variations in the ratio of NADH and NADPH oxidase activities indicate that separate systems exist for the oxidation of exogenous redox equivalents by mitochondria of C. utilis. Variation of the NADPH requirement for biomass formation by applying different growth conditions did not result in significant changes in NADPH oxidase activities of mitochondria. It is concluded that in C. utilis NADPH can be used in dissimilatory processes for the generation of ATP.