Separation and characterization of mares' milk alpha(s1)-, beta-, kappa-caseins, gamma-casein-like, and proteose peptone component 5-like peptides.
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.
Egito
A S
AS
Laboratoire des BioSciences de l'Aliment, UC885 INRA, Faculté des Sciences et Techniques, Université Henri Poincaré-Nancy 1, Vandoeuvre-lès-Nancy, France.
Miclo
L
L
López
C
C
Adam
A
A
Girardet
J M
JM
Gaillard
J L
JL
D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D002614:Chelating Agents / Q000737:chemistry* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D002852:Chromatography, Ion Exchange / Q000662:veterinary; D015180:Electrophoresis, Gel, Two-Dimensional / Q000662:veterinary; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D005260:Female; D006736:Horses / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008892:Milk / Q000737:chemistry*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D002364:Caseins; D002614:Chelating Agents; D010446:Peptide Fragments; C018135:proteose-peptone