Heterogeneity and Composition of k-Casein from Bovine Colostrum

抄録

The heterogeneity and chemical composition were investigated in k-casein from colostrum. The acid casein was obtained from four different Holstein cow colostra. The yield of acid casein from colostrum was higher than that from normal milk. k-Casein from colostrum was prepared by the gel filtration method of Yaguchi et al. The gel filtration profiles differed among the four colostrum acid caseins.
Colostrum k-casein was fractionated on a DEAE-cellulose column into one nonadsorbed and six adsorbed fractions with increasing salt concentration. Six adsorbed fractions had the same molecular weight and stabilizing ability for α_s1 -casein in the presence of calcium ion. The amino acid composition and the phosphorus content of the adsorbed fractions were iden-tical, but fractions eluted with high salt concentrations had more carbohydrates (galactose, sialic acid, glucosamine, galactosamine). Colostrum k-casein was characterized by a higher content of carbohydrate moiety in comparison with normal k-casein. Also glucosamine which has not been found in normal k-casein was detected in colostrum K-casein. The k-casein com-ponent from colostrum contained at least one molecule of carbohydrate, though the carbo-hydrate-free component was detected in normal k-casein.