Saccharomyces carlsbergensis cells were found to store about 10% of the glucose taken up as glycogen during oscillatory glycolysis. 2. Under the same conditions and during all phases of carbohydrate limited growth, glycogen synthase (E.C. 2.4.1.11), in the absence of glucose 6-phosphate, had only 5--20% activity compared to the activity in the presence of 10 mM of the effector, indicative for the D-form of the enzyme. 3. Inorganic phosphate (intracellular concentration 19--23 mumoles/g yeast) strongly inhibited glycogen synthase both in the absence of glucose 6-phosphate and competitively to this effector. 4. In this yeast, the D-form of glycogen synthase had to be active to account for the high rate of glycogen synthesis. The resulting sensitivity to glucose 6-phosphate may lead to a pulsatory action of the enzyme during oscillatory glycolysis.
