Proteolytic specificity of chymosin on bovine alpha s1-casein.
The proteolytic specificity of chymosin (EC 3.4.23.4) on bovine alpha s1-casein at 30 degrees C in phosphate buffer, pH 6.5 and at pH 5.2 in the presence of 5% (w/v) NaCl was investigated. Peptides (pH 4.6-soluble) were isolated by reversed-phase HPLC and identified from their amino acid sequence; the identity of some peptides was confirmed by mass spectrometry and/or amino acid composition. The small peptides produced at pH 6.5 were Arg1-Phe23, Phe24-Phe28, Phe24-Leu40(?), Phe150-Phe153, Phe150-Leu156, Tyr154-Tyr159, Tyr154-Trp164, Asp157-Trp164 and Tyr165-Trp199. The same peptides, except Tyr154-Trp164, were produced at pH 5.2 in the presence of NaCl and, in addition, the peptides Arg1-Leu11, Phe24-Phe32, Lys102-Leu142, Ala143-Leu149 and Tyr165-Phe179. The rates of production of individual peptides differed under the two conditions studied but Arg1-Phe23 and Tyr165-Trp199 were the first and second peptides produced under both conditions. Pathways are proposed to interpret the proteolysis of alpha s1-casein in solution under the conditions of this study.
Center for Dairy Research, University of Wisconsin-Madison 53706.
P L
PL
McSweeney
N F
NF
Olson
P F
PF
Fox
A
A
Healy
P
P
Højrup
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002364:Caseins / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D012085:Chymosin / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007716:Kluyveromyces / Q000201:enzymology; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D013997:Time Factors
D000596:Amino Acids; D002364:Caseins; D011994:Recombinant Proteins; D012085:Chymosin