New insights into a mutant of Saccharomyces cerevisiae having impaired sugar uptake and metabolism

Summary A regulatory mutant of Saccharomyces carlsbergensis unable to inactivate fructose-1,6-bisphosphatase was shown to have a normal response to the glucose signal as measured by trehalase and 6-phosphofructose-2-kinase activities. The level of fructose 2,6-bisphosphate, however, was found to be 4- to 5-fold lower than that found in the wild-type strain. A rapid and drastic depletion in ATP was confirmed. A partial revertant for growth on glucose which retained its inability to grow on fructose did not show normal levels of fructose 2,6-bisphosphate; however, ATP levels were restored. Trehalose-6-phosphate synthase activity was found in its phosphorylated, less active form. A high degree of phosphorylation at the level of enzymatic activity and of the sugar phosphorylating systems might be responsible for the impairment of control between hexose transport and metabolism, as well as for the absence of trehalose accumulation.Abbreviations F2,6P₂ fructose 2,6-bisphosphate - PFK1 6-phosphofructose-l-kinase - FBPasel fructose-1,6-bisphosphatase - PFK2 6-phosphofructose-2-kinase - PEP phosphoenolpyruvate