Minor components of reduced bovine kappa-casein

Bovine kappa-casein reduced with 2-mercaptoethanol was fractionated on a DEAE-cellulose column to one nonadsorbed, five major adsorbed and two minor adsorbed fractions. The properties of the nonadsorbed and five major adsorbed fractions were reported in our previous paper (4). In this paper, the characteristics of two minor adsorbed fractions (P-X and P-Y) were reported. Gel electrophoretic patterns of these fractions were similar to kappa-casein. These fractions had the same amino acid composition and the same phosphorus content as the major components. P-X contained one residue each of N-acetylneuraminic acid, galactose and galactosamine, and P-Y two residues each. Furthermore, these fractions showed the stabilizing ability for alpha s1-casein in the presence of calcium ion. These results indicate that P-X and P-Y are minor components of reduced bovine kappa-casein.