title: Three yeast proteins that specifically inhibit yeast proteases A, B, and C.
abstract: Baker's yeast was found to contain inhibitors of yeast proteases A and C. These two proteins were partially purified, characterized, and compared with the previously described inhibitor of protease B. The A and B inhibitors were very thermostable and were extracted from intact yeast cells at 9k C. The A inhibitor appeared to be a protein with a molecular weight of about 22,000 which could be dissociated into two monomers or chains, both of which had a molecular weight of approximately 11,000. The protease C (carboxypeptidase Y)-inhibitor complex was purified and then partially disociated on an ion-exchange column. The free protease C inhibitor was very unstable, possibly because of destruction by a contaminating protease. Each inhibitor was specific for its corresponding protease and each inhibition was competitive. Whereas proteases A, B, and C destroyed the B inhibitor, only protease B had a pronounced destructive effect on the protease A inhibitor. Pepstatin was found to be a selective inhibitor of protease A, whereas chymostatin and antipain specifically inhibited protease B.
mesh_terms: D002268:Carboxypeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002474:Cell-Free System; D002848:Chromatography, DEAE-Cellulose; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000032:analysis; D005656:Fungal Proteins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007976:Leupeptins; D008970:Molecular Weight; D010436:Pepstatins; D010447:Peptide Hydrolases / Q000378:metabolism; D011480:Protease Inhibitors; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D015003:Yeasts / Q000032:analysis
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D007976:Leupeptins; D010436:Pepstatins; D011480:Protease Inhibitors; D002268:Carboxypeptidases; D010447:Peptide Hydrolases