Characterization of mare caseins. Identification of $\alpha_{{\bf S1}}$- and $\alpha_{{\bf S2}}$- caseins
Year: 2000
Type: article
Abstract: Whole mare (Mongolian and French breeds) casein was obtained from skim milk by isoelectric precipitation (pH 4.6) at 22 °C.In another series of experiments, equine caseins were fractionated after isoelectric precipitation at 4 °C, according to their sensitivity to temperature, on one hand, the pH of the resulting pellet was adjusted to 6.5 before centrifugation (45 000 g for 30 min) at 4 °C; on the resulting casein fraction which precipitated was named the cold precipitated (CP) fraction.On the other hand, the supernatant obtained from the centrifugation of skim milk at pH 4.6 and 4 °C was warmed to 30 °C before being centrifuged at 30 °C, 45 000 g, for 30 min.The resulting casein fraction which precipitated was named the thermally precipitated (TP) fraction.Equine caseins were then purified by high resolution gel chromatography on an anion-exchange column followed by reversed phase-high performance liquid chromatography.The casein fractions were analyzed by urea-and SDS-polyacrylamide gel electrophoresis, their amino acid compositions were determined and their first 15 N-terminal amino acids were sequenced.This analysis showed the presence of α slike caseins isolated from the CP fraction.α s1 -Like-casein showed 4 major double bands by electrofocusing with a pI range of 4.3-4.8.In the same conditions, α s2 -like casein showed 2 major bands with a pI range of 4.3-5.1.The TP fraction revealed the existence in equine milk of 6 subfractions of β-like caseins, occurring in the following ratios: 1:5:18:20:15:10, differing at least in their degree of phosphorylation (as shown also by the action of acid phosphatase).Since no evidence of the presence of κ-casein was found in equine milk, it is proposed that part of its functions in the milk of the Equidae could be assumed by the population of less phosphorylated β-caseins.mare milk / α s1 -casein / α s2 -casein / β-casein Résumé -Caractérisation des caséines du lait de jument.Identification des caséines α S1 et α S2 .La caséine entière de lait écrémé de juments issues de troupeaux de Mongolie et de France a été obtenue par précipitation isoélectrique (pH 4,6) à 22 °C.Par ailleurs, les caséines équines ont été Lait 80
Source: Le Lait
DOI: 10.1051/lait:2000121
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2107583708