Catabolite inactivation of gluconeogenic enzymes in mutants of yeast deficient in proteinase B.

Strains of Saccharomyces cerevisiae bearing nonsense mutations in the structural gene for proteinase B (EC 3.4.22.9) have been examined for the ability to make the transition from growth on acetate to growth on glucose and for the ability to inactivate three glucoeogenic enzymes during the transition because proteinase B has been proposed by others to be responsible for the inactivation of the three enzymes during the growth transition. The mutant strains make the growth transition normally. Catabolite inactivation of hexosediphosphatase (D-fructose-1,6-biphosphate 1-phosphohydrolase, EC 3.1.3.11), malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37), and phosphoenolpyruvate carboxykinase (ATP) [ATP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.49] occurred in prb1 mutants with kinetics similar to those seen in wild-type strains. We infer that proteinase B activity is not essential for the process of catabolite inactivation.