title: Hormone processing and membrane-bound proteinases in yeast.
abstract: A search for maturating peptidases of the precursor protein of the mating hormone (pheromone) alpha-factor of Saccharomyces cerevisiae was performed using short model peptides representing those sequences of the precursor protein, where cleavage is thought to occur in vivo. This search was done in a mutant lacking several of the unspecific vacuolar peptidases. The chromogenic peptide Cbz-Tyr-Lys-Arg-4-nitroanilide led to the detection of a membrane-bound enzyme called proteinase yscF. Cleavage of the synthetic peptide derivative occurs after the basic amino acid pair, a proposed signal for hormone processing. Optimum pH for the reaction is 7.2. The enzyme does not cleave after single basic amino acid residues indicating that it is distinct from trypsin-like proteinases. Proteolytic activity is enhanced by Triton X-100. The enzyme is strongly inhibited by EGTA, EDTA and mercurials but insensitive to phenylmethylsulfonyl fluoride. The enzyme activity is strongly dependent on Ca2+ ions. In a mutant (kex2), which accumulates an over-glycosylated alpha-factor precursor, no proteinase yscF activity can be found. Membrane-bound peptidase activity possibly involved in removal of the arginyl and lysyl residues remaining at the carboxy terminus of the alpha-factor pheromone peptide after the initial cut of the precursor molecule could be identified by using the model peptides Cbz-Tyr-Lys-Arg and Cbz-Tyr-Lys.
mesh_terms: D000818:Animals; D002268:Carboxypeptidases / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism*; D008566:Membranes / Q000201:enzymology; D009842:Oligopeptides / Q000378:metabolism; D010675:Pheromones / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D010675:Pheromones; D011498:Protein Precursors; D002268:Carboxypeptidases; D010450:Endopeptidases