Comparative study of methods for the isolation and purification of bovine κ-casein and its hydrolysis by chymosin
| Autor: | John Stephen Ayers, Tim Coolbear, Kate P. Coolbear, David Francis Elgar |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
chemistry.chemical_classification
Gel electrophoresis Chromatography Hydrolysis Caseins General Medicine Fractionation Reversed-phase chromatography Hydrogen-Ion Concentration High-performance liquid chromatography Peptide Fragments Enzyme chemistry Casein Animals Cattle Animal Science and Zoology Chymosin Chromatography High Pressure Liquid Food Science |
| Zdroj: | Journal of Dairy Research. 63:61-71 |
| ISSN: | 1469-7629 0022-0299 |
| DOI: | 10.1017/s002202990003154x |
| Popis: | Summaryκ-Casein was purified from a single batch of whole acid casein (κ-A variant) using different methods in order to compare their merits in producing a purified material with a carbohydrate and phosphate heterogeneity representative of the whole κ-casein complement in milk. Ion-exchange methods of purification gave products of higher purity than precipitation techniques involving final purification by ethanol fractionation, but all methods resulted in κ-caseins of apparently similar heterogeneity and chemical composition. The purified κ-caseins were hydrolysed with chymosin and the derived macropeptides isolated. These were all virtually identical as determined by reversed-phase chromatography and gel electrophoresis. Some observations on chymosin hydrolysis of κ-casein were made. In addition to formation of the major para-κ-casein (Glu1–Phe105) and macropeptide (Met106–Val169), chymosin hydrolysis at pH 6·6 also resulted in two minor para-κ-caseins with N-termini corresponding to Phe18and Ser33of κ-casein. At pH 5·5 and 4·5 para-κ-casein was rapidly hydrolysed into at least six fragments, one of which had an N-terminus corresponding to Trp76of κ-casein. At pH 6·6, 5·5 and 4·5 the κ-casein macropeptide was stable to chymosin, but at pH 2·3 it was hydrolysed by chymosin into fragments with N-termini corresponding to Met106, He125, Ala138, Val139, Thr145and Glu147of κ-casein. |
| Databáze: | OpenAIRE |
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