Glucose Repression in Yeast Cells. Comparison of the Effect of Galactose with that of Glucose on the Formation of Respiratory Enzymes and Cytochromes

Abstract

The effect of glucose and galactose on the formation of respiratory enzymes and cytochromes in yeast cells was compared both in aerobic culture and during adaptation of anaerobically grown cells to oxygen. (1) In aerobic culture, activities of reduced nicotinamide-adenine dinucleotide (NADH) cytochrome c reductase and malate dehydrogenase and QO₂ of cells were reduced considerably with increasing concentration of glucose in the medium. On the other hand, galactose did not repress NADH cytochrome c reductase significantly and QO₂ of cells was not reduced with increasing concentration of gllactose in the growth medium, although it slightly repressed malate dehydrogenase. (2) Formation of cytochromes, and NADH cytochrome c reductase and malate dehydrogenase during the adaptation of anaerobic cells to oxygen were inhibited by a high concentration of glucose but not by galactose, and glucose was consumed rapidly but galactose was consumed slowly. On the other hand, when yeast cells grown anaerobically in the presence of galactose were transferred to aerobic culture in the presence of galactose, it was consumed rapidly and the formation of cytochromes, NADH cytochrome c reductase and malate dehydrogenase was inhibited. NADH ferricyanide reductase activity did not changed significantly during the adaptation of anaerobic cells to oxygen.