Loss of sporulation ability in a yeast mutant with low proteinase a levels

Intracellular proteolytic enzymes are assumed to play key roles in the regulation of vegetative growth and of differentiation, i.e., sporulation, of Saccharomyces cerevisiae [l-7]. Up to now, two endoproteinases (A, B), two carboxypeptidases (S, Y) and three aminopeptidases have been identified in this organism (reviewed in [2,7]). Despite the recent isolation of mutants lacking carboxypeptidase Y or proteinase B activity, however, so far no abnormalities in the growth or sporulation behaviour of proteinasedeficient yeast cells have been described [8,9]. Some properties of a mutant with low proteinase A activity and defective in sporulation are reported here.