title: Mutant defective in processing of an enzyme located in the lysosome-like vacuole of Saccharomyces cerevisiae.
abstract: Carboxypeptidase Y, a vacuolar enzyme in Saccharomyces cerevisiae, is synthesized as a larger precursor whose apparent molecular mass is approximately 67,000 daltons. We have characterized a recessive mutation, pep4-3, that prevents maturation of this precursor. The accumulated precursor does not possess enzymatic activity. We have shown that the precursor accumulating in the pep4-3 mutant is not produced in a doubly mutant strain that also bears a mutation in the carboxypeptidase Y structural gene that eliminates production of carboxypeptidase Y. We have also shown that a nonsense fragment of carboxypeptidase Y is processed. Although there is evidence that proteinase B can catalyze the conversion of the precursor to a mature form in vitro, nonsense mutations in the structural gene for proteinase B, PRB1, do not affect the levels of carboxypeptidase Y activity, and strains bearing these mutations produce a carboxypeptidase Y of apparently normal size. Hence, proteinase B is not essential for the maturation of carboxypeptidase Y precursor in vivo. The pep4-3 mutation affects at least five vacuolar enzymes. This suggests that there is a processing event common to all of these enzymes.
mesh_terms: D016282:Aspartic Acid Endopeptidases; D002268:Carboxypeptidases / Q000096:biosynthesis*; D043402:Cathepsin A; D010450:Endopeptidases / Q000378:metabolism; D009154:Mutation; D009940:Organoids / Q000201:enzymology*; D011498:Protein Precursors / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases; D014617:Vacuoles / Q000201:enzymology*
chemical_list: D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; D002268:Carboxypeptidases; D010450:Endopeptidases; D043402:Cathepsin A; C499283:PRC1 protein, S cerevisiae; C022633:serine carboxypeptidase; D012697:Serine Endopeptidases; C023302:yeast proteinase B; C022325:aspartic proteinase A; C499267:PEP4 protein, S cerevisiae; D016282:Aspartic Acid Endopeptidases