title: Proteolysis of bovine alpha s2-casein by chymosin.
abstract: Proteolysis of bovine alpha s2-casein by chymosin (E. C. 3.4.23.4) in solution in 100 mM Na phosphate buffer, pH 6.5, at 30 degrees C was studied by reversed-phase (RP)-HPLC and urea-polyacrylamide gel electrophoresis (PAGE). Chymosin hydrolyzed alpha s2-casein in solution to eight peptides detectable by urea-PAGE. Peptides soluble in acetate buffer, pH 4.6, were isolated by RP-HPLC on a C18 column using an acetonitrile/water gradient and identified from their N-terminal amino acid sequence. The chymosin cleavage sites were at the bonds Phe88-Tyr89, Tyr95-Leu96, Gln97-Tyr98, Tyr98-Leu99, Phe163-Leu164, Phe174-Ala175 and Tyr179-Leu180. Chymosin cleavage sites were restricted to the hydrophobic regions of the molecule. The bond-type in alpha s2-casein cleaved by chymosin was in agreement with that found to be susceptible to chymosin in other caseins. The primary site of chymosin action on alpha s2-casein appeared to be at Phe88-Tyr89.
authors.affiliation: Center for Dairy Research, University of Wisconsin, Madison 53706.
authors.forename: P L
authors.initials: PL
authors.lastname: McSweeney
authors.forename: N F
authors.initials: NF
authors.lastname: Olson
authors.forename: P F
authors.initials: PF
authors.lastname: Fox
authors.forename: A
authors.initials: A
authors.lastname: Healy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D012085:Chymosin / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D002364:Caseins; D011994:Recombinant Proteins; D012085:Chymosin