Metabolic imbalance in a Saccharomyces cerevisiae mutant unable to grow on fermentable hexoses.

A mutant of Saccharomyces cerevisiae unable to grow on fermentable hexoses has been studied. The mutant grew normally on galactose or maltose. It was also able to grow on a medium containing glucose or fructose with a 25-fold excess of D-xylose. Assay of the glycolytic enzymes in vitro did not show differences between the parental and the mutant strains. Upon addition of fructose, metabolites up to triose phosphates accumulated and the ATP dropped to low levels. It is proposed that an imbalance between the initial and final segments of glycolysis that depletes the cell of ATP produces the observed phenotype.