Phosphorylation of 3-O-methyl-D-glucose and catabolite repression in yeast

The glucose analog, 3-O-methyl-d-glucose, inhibited growth of yeast on non-fermentable carbon sources. The sugar was phosphorylated by the yeast and also in vitro, by a commercial preparation of yeast hexokinase. The chromatographic behaviour of the phosphorylated product was identical in both cases. This suggests that 3-O-methyl-d-glucose is phosphorylated to form 3-O-methyl-d-glucose 6-phosphate. The inhibition of the growth appears to be due to interference with the derepression of several enzymes necessary to grow on non-fermentable carbon sources. Spontaneous mutants whose growth was unaffected by 3-O-methyl-d-glucose were isolated. In these mutants there was no significant accumulation of the phosphorylated ester and the derepression of the enzymes tested was not affected by the glucose analog.This work has benefited from a grant of the Spanish Comisibn Asesora de Investigación Científica y Técnica