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

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Abstract
The glucose analog, 3-O-methyl-D-glucose, inhibited growth of yeast on non-fermentable C sources. The sugar was phosphorylated by the yeast and also in vitro by a commercial preparation of yeast hexokinase. The chromatographic behavior 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 apparently is due to interference with the derepression of several enzymes necessary to grow on non-fermentable C 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.