Activities and cellular localization of yeast proteases and their inhibitors

We have found that proteases A, B and C of Saccharomyces cerevisiae are localized in the vacuole. The corresponding inhibitors of these three proteases are present in the extravacuolar cytosol. The compartmentation of the yeast proteases suggests that their function is primarily the intravacuolar digestion of proteins. Yearst cells were grown under various conlitions, and it was found that culture conditions which either induce biochemical differentiation of cells or which do not allow growth result in the enhancement of proteolytic activities.