Casein. VIII. Isolation of a Glycopeptide from an Enzymic Hydrolysate of κ-Casein

K-Casein was hydrolyzed with Pronase P and the resultant hydrolysate was fractionated on Sephadex G-50. A glyeopeptide was isolated which contained approximately 64% total carbohydrate (hexose, hexosamine, sialic acid) and no detectable amount of phosphorus. Calculations based on the amino acid composition of the glycopeptide gave a minimal molecular weight of 11,000. The glycopeptide had no N-terminal amino acid and carboxypeptidase liberated only serine. On the basis of a molecular weight of 11,000, the peptide contained 39 amino acid residues (11 threoninc, 7 serine) and 6, 14, and 16 residues of sialic acid, hexose, and hexosamine, respectively.