INDUCTION OF SPECIFIC ENZYMES OF THE OXIDATIVE PENTOSE-PHOSPHATE PATHWAY BY GLUCONO-DELTA-LACTONE IN SACCHAROMYCES-CEREVISIAE

Growth of Saccharomyces cerevisiae on D-glucono-delta-lactone (deltagl) 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 deltagl, 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 deltagl, was found to have recovered normal dehydrogenase activity and the ability to synthesize the three enzymes when induced by deltagl. Another class of deltagl-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 deltagl. 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 deltagl.