EXTRACELLULAR REDUCTION OF MENADIONE AND FERRICYANIDE IN YEAST-CELL SUSPENSION

Extracellular reduction of menadione and ferricyanide were promoted by glucose rather than ethanol in a yeast cell (Saccharomyces cerevisiae IFO 2044) suspension. NAD(P)H: menadione oxidoreductase from yeast pl asma membrane possessing ferricyanide reductase activity had higher su bstrate specificity for NADH than for NADPH. Glucose produced a transi ent increase in NADH content in the absence of menadione, but neither glucose nor ethanol restored the NADH content upon menadione-catalyzed ferricyanide reduction. These findings suggest that the NADH content is controlled by the metabolism of glucose and ethanol, and that the e xcess of NADH generated by glucose and ethanol is effectively consumed by NADH:menadione oxidoreductase in the yeast transplasma membrane re dox system.