The effect of mutation on two forms of phosphoglucomutase in Saccharomyces

The Saccharomyces haploid stock 8050B is a galactose fermenter which was found by chromatography on CM-cellulose and electrophoresis on agar gel to contain a major and a minor form of phosphoglucomutase (d-glucose-1,6-diphosphate:d-glucose-1-phosphate phosphotransferase, EC 2.7.5.1). Mutations in the Ga₅ locus of this stock reduced the phosphoglucomutase activity in extracts 4–5-fold and rendered the cells unable to ferment galactose. The reduction in enzyme activity of the mutants was shown to be due to the fact that the synthesis of the major phosphoglucomutase component was blocked, although the minor component was not affected. The two phosphoglucomutases are probably the products of different genes.