Genetical and Biochemical Studies of Glucosephosphate Isomerase Deficient Mutants in Saccharomyces cerevisiae

Abstract

A number of glucose-negative mutants of Saccharomyces cerevisiae were isolated and shown to contain very low activities of glucosephosphate isomerase. Mutants almost totally lacking this enzyme (less than 1% of wild-type activity) grew on fructose if provided with a small quantity of glucose. Larger amounts of glucose led to the accumulation of glucose 6-phosphate and growth inhibition. These mutants did not grow on galactose. Other mutants with low enzyme activities (about 1% of wild type) grew on fructose alone and also on galactose. The mutant characters were determined in both cases by single gene mutations which were mapped on chromosome II and, presumably, identify a structural gene locus for the enzyme.