Three parameters participating in the specific control of proteolytic processes in intact yeast cells are discussed: (1) different substrate specificity of the yeast proteinases A and B, and carboxypeptidase Y when tested with yeast enzymes as substrate, (2) three types of macro- molecular inhibitors from yeast specifically inhibiting the three pro- teinases, (3) subcellular localization of the proteinases in the vacu- oles and of the inhibitors in the cytosol. Mechanisms of a selective proteolysis of single enzymes or a group of enzymes dependent on chan- ges in the physiological conditions...