Abstract
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.
Original language | English |
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Journal | Journal of Dairy Research |
Volume | 60 |
Issue number | 3 |
Pages (from-to) | 401-12 |
Number of pages | 12 |
ISSN | 0022-0299 |
Publication status | Published - Aug 1993 |
Keywords
- Amino Acid Sequence
- Amino Acids/analysis
- Animals
- Caseins/chemistry
- Cattle
- Chromatography, High Pressure Liquid
- Chymosin/metabolism
- Electrophoresis, Polyacrylamide Gel
- Hydrogen-Ion Concentration
- Hydrolysis
- Kluyveromyces/enzymology
- Mass Spectrometry
- Molecular Sequence Data
- Recombinant Proteins/metabolism
- Sequence Analysis, DNA
- Substrate Specificity
- Time Factors