DECREASE IN GLYCOLYTIC FLUX IN SACCHAROMYCES-CEREVISIAE CDC35-1 CELLSAT RESTRICTIVE TEMPERATURE CORRELATES WITH A DECREASE IN GLUCOSE-TRANSPORT

The glycolytic flux was investigated in the thermosensitive Saccharomy ces cerevisiae adenylate cyclase mutant cdc35-1. Directly after a shif t to restrictive temperature. the specific CO2 production rate increas ed from about 250 nmol min(-1) (mg protein)(-1) to more than 400 nmol min(-1) (mg protein)(-1), but then the CO2 production gradually fell t o about 70 nmol min(-1) (mg protein)(-1) after 5 h. O-2 consumption at restrictive temperature continued at more or less the same rate as at permissive temperature. The temperature shift in the mutant resulted in an increase in the estimated intracellular cAMP concentration from about 1.1 mu M to 1.8 mu M. This indicates that high cAMP levels are n ot sufficient for cell cycle progression and high glycolytic activity. The decrease in glycolytic activity at restrictive temperature was no t paralleled by a similar decrease in the specific activity of any of the glycolytic enzymes, but correlated with a decrease in hexose trans port. A drop in intracellular concentrations of the early metabolites of glycolysis further indicated a defect in transport at restrictive t emperature. Our data suggest that glucose transport has a high control on glycolytic flux.