Effect of glucose on the activity and the kinetics of the maltose-uptake system and of α-glucosidase in Saccharomyces cerevisiae

Abstract

1. 1. During incubation of maltose-grown Saccharomyces cerevisiae cells in nutrient medium with glucose, the maltose-uptake system was almost completely inactivated within 90 min. During this deadaptation, the Km of the maltose-uptake system increased from 4 to 50 mM. 2. 2. The activity of α-glucosidase ( glucohydrolase, EC 3.2.1.20) remained rather constant during incubation of maltose-grown cells in a nutrient medium with glucose. 3. 3. The presence of maltose in the nutrient medium with glucose did not protect the maltose-uptake system against inactivation. The inactivation was scarcely affected by partial inhibition of glycolysis or by anaerobiosis during deadaptation. Incubation with ethanol did not inactivate the uptake system. Cycloheximide in the medium with glucose led to a two-fold slower inactivation either by inhibiting the protein synthesis or by interfering with the glucose metabolism. 4. 4. A rapid recovery of the maltose-uptake system occurred when inactivated cells were incubated in a maltose nutrient medium; protein synthesis appeared to be a prerequisite for the recovery process.