Abstract
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.