Carboxy-terminal processing of the mating pheromone α-factor of the yeast Saccharomyces cerevisiae has been assumed to be due to the action of carboxypeptidase yscα. [(1985) EMBO J. 4, 173–177]. Here it is shown that a mutant (kex1) defective in α-factor maturation is defective in carboxypeptidase yscα activity, indicating that the enzyme is indeed the processing catalyst. It is proposed that carboxypeptidase yscα is the product of the KEX1 gene.
