Effect of different carbon sources on the regulation of carbohydrate metabolism inSaccharomyces cerevisiae

The carbohydrate metabolism ofSaccharomyces cerevisiae is strongly influenced by the concentration and the nature of the carbon source. As long as glucose is present in the growth medium, the cells possess a predominantly glycolytic pathway of degradation and low levels of α-glucosidase and of those enzymes of the citric-acid cycle, the respiratory chain, and the glyoxylate cycle, which are localized in the mitochondria. After the depletion of glucose the level of these enzymes rises considerably. As long as the carbon source can be demonstrated in the medium, maltose-grown cells have a greater oxidative activity and a higher level of these enzymes than glucose-grown cells, unlike glucose-grown cells they easily adapt to ethanol and acetate. Catabolite repression is suggested as an important factor in the regulation of synthesis of enzymes of the citric-acid cycle, the glyoxylate cycle and the respiratory chain. There is an obvious correlation between the regulation of α-glucosidase and of the enzymes of oxidative carbohydrate metabolism.