Induction of specific enzymes of the oxidative pentose phosphate pathway by glucono-Δ-lactone in Saccharomyces cerevisiae

Abstract

Growth of Saccharomyces cerevisiae on D-glucono-Δ -lactone (Δ gl) was found to be associated with a specific coordinate induction of the synthesis of two enzymes of the oxidative pentose phosphate pathway - 6-phosphogluconate dehydrogenase and 6-phosphogluconolactonase - together with that of a third enzyme, gluconokinase. The gnd1 mutation, responsible for an approximately 80% loss of 6-phosphogluconate dehydrogenase activity and the inability of the cells to grow on Δ gl, completely abolished the induction of all three enzymes, while the gnd2 mutation affected this only partially. One class of gnd1 revertants, selected for growth on Δ gl, was found to have recovered normal dehydrogenase activity and the ability to synthesize the three enzymes when induced by Δ gl. Another class of Δ gl-positive revertants possessed constitutively elevated levels of gluconokinase. In contrast, glucose-positive revertants of gnd1, with restored constitutive dehydrogenase activity, continued to remain deficient in induction of the three enzymes and also failed to grow on Δ gl. Induction of 6-phosphogluconate dehydrogenase activity was associated with increased transcription of the gene coding for the major isoenzyme; the transcript remained undetectable in the gnd1 mutant. Induction of these specific enzymes thus appears to be essential for growth of S. cerevisiae on Δgl.