Fifty-nine mutants with reduced ability to cleave the chymotrypsin substrate N-acetyl-DL-phenylalanine P-naphthyl ester have been isolated in S. cerevisiae. All have reduced levels of one o r more of the three well-characterized proteinases in yeast. All have reduced levels of proteinase C (carboxypeptidase Y). These mutations define 16 complementation groups. HREE proteinases that have been ch...