Separation and characterization of mares' milk alpha(s1)-, beta-, kappa-caseins,gamma-casein-like,and proteose peptone component 5-like peptides |
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Authors: | Egito A S Miclo L López C Adam A Girardet J M Gaillard J L |
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Affiliation: | Laboratoire des BioSciences de l'Aliment, UC885 INRA, Faculté des Sciences et Techniques, Université Henri Poincaré-Nancy 1, Vandoeuvre-lès-Nancy, France. |
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Abstract: | The equine alpha(s1)- and beta-caseins (CN) were purified by chromatography on DEAE-cellulose and by reversed-phase HPLC. The alpha(s1)-, beta-, and kappa-CN were characterized either by monodimensional urea-PAGE or sodium dodecylsulfate (SDS)-PAGE or by bidimensional electrophoresis. Kappa-casein was characterized after electrophoresis by glycoprotein-specific staining. To identify alpha(s1)-CN without ambiguity, internal sequences were determined after trypsin or chymosin digestion of purified alpha(s1)-CN. These sequences, that could be estimated to correspond to 62% of the full protein, presented strong identities with regions of alpha(s1)-CN primary structures of other species. In particular, 51, 48, 43, and 40% identities were obtained with corresponding regions of sow, dromedary, cow, and human alpha(s1)-CN, respectively. On the other hand, trace amounts of equine gamma-CN-like and proteose peptone component 5-like peptides were found in the whole CN. They were identified by microsequencing and corresponded to beta-CN peptides generated by plasmin action on the whole CN. The equine alpha(s1), beta-, and kappa-CN were separated by bidimensional electrophoresis in numerous isoelectric variants with apparent isoelectric points distributed between pH 4.4 to 6.3, 4.4 to 5.9, and 3.5 to 5.5, respectively. The beta- and kappa-CN displayed a more acidic character in the mare than in the cow. |
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Keywords: | bidimensional electrophoresis equine casein mare's milk plasmin) |
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