Preparation and fractionation of goat kappa-casein: analysis of the glycan and peptide components.

Whole goat kappa-casein was prepared by chromatography of whole casein on hydroxyapatite. Chromatography of whole kappa-casein on DEAE-cellulose separated 5 fractions. All of them were sensitive to chymosin. Their amino acid and carbohydrate composition, phosphate content and molecular weight were determined. Galactose, N-acetylgalactosamine, N-acetyl and N-glycolyl neuraminic acids were identified in whole kappa-casein. It appears that goat kappa-casein, like cow, buffalo and ewe kappa-caseins, is composed of several fractions having identical peptide chains and differing in their carbohydrate contents. The main fraction, devoid of carbohydrate, was treated with chymosin. The para-kappa-casein and caseinomacropeptide were isolated. Their amino acid composition and phosphate content were determined.