title: Proteolytic activity of proteinases on macropeptide isolated from kappa-casein.
abstract: Proteolytic activities of chymosin, bovine pepsin, Mucor miehei rennet, Cryphonectria parasitica (formerly Endothia parasitica) rennet, trypsin, and chymotrypsin on kappa-casein macropeptide were measured. Macropeptide solutions (10 mg/ml of .05 M, pH 6.6 phosphate buffer) were incubated with the enzymes at 37 degrees C for various times, and their reactions were stopped by adding .025 ml of pepstatin (1 mg/ml of methanol). Peptides released from kappa-casein macropeptide were then fractionated using reverse-phase HPLC. At the pH of milk (pH 6.6), kappa-casein macropeptide was resistant to enzymic action by chymosin, bovine pepsin, and M. miehei and C. parasitica rennets. Bovine pepsin hydrolyzed kappa-casein macropeptide at pH 3. kappa-Casein macropeptide was readily hydrolyzed at pH 6.6 by trypsin and chymotrypsin. Possible physiological functions of the kappa-casein macropeptide are discussed in light of these findings.
authors.affiliation: Department of Nutrition and Food Sciences, Utah State University, Logan 84322-8700.
authors.forename: K M
authors.initials: KM
authors.lastname: Shammet
authors.forename: R J
authors.initials: RJ
authors.lastname: Brown
authors.forename: D J
authors.initials: DJ
authors.lastname: McMahon
mesh_terms: D002240:Carbohydrate Sequence; D002364:Caseins / Q000378:metabolism*; D012085:Chymosin / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D002364:Caseins; D010455:Peptides; C025350:rennet; D010450:Endopeptidases; D002918:Chymotrypsin; D014357:Trypsin; D012085:Chymosin