| Abstract: | A mutant of Saccharomyces cerevisiae deficient in phosphoglucoisomerase (EC 5.3.1.9) is described. It does not grow on glucose or sucrose but does grow on galactose or maltose. Addition of glucose to cultures growing on fructose, mannose, or acetate arrests further growth without altering viability; removal of glucose permits resumption of growth. Glucose causes accumulation of nearly 30 mumoles of glucose-6-phosphate per g (wet weight) of cells and suppresses synthesis of ribonucleic acid. Inhibition of growth by glucose does not appear to be due to a loss of adenosine triphosphate or inorganic orthophosphate. The mutant, however, utilizes glucose-6-phosphate produced intracellularly. Release of carbon dioxide from specifically labeled glucose suggests a C-l preferential cleavage. The kinetics of glucose-6-phosphate accumulation during glucose utilization in the mutant is not consistent with the notion that the utilization of glucose is controlled by glucose-6-phosphate. |
