Induction of the glyoxylate cycle in Tetrahymena

Abstract The activities of glyoxylate cycle enzymes and the incorporation of acetate-C 14 into metabolic intermediates during the induction of stationary phase in growing cultures of Tetrahymena pyriformis GL were determined. The specific activities of the glyoxylate cycle enzymes, isocitrate lyase and malate synthase, doubled in the stationary cells; at the same time, the activities of acetyl-coenzyme A synthase and malate dehydrogenase did not change significantly. The ratio of radioactivity in malate and aspartate to that in citrate and glutamate changed from 0.45 in log-phase suspensions to 1.5 in suspensions of induced stationary phase cells. The increased cellular capacity for glyconeogenesis from acetate could be accounted for by the increased metabolic role of the glyoxylate cycle.