Carbohydrates of bovine κ-casein

Abstract

SummaryComparison of the carbohydrates of κ-casein with those of the glycopeptides released by the action of rennin on whole milk showed that there are consistent differences between them, which are due to the presence of carbohydrates in para-κ-casein. d-Mannose, d-galactose, 2-acetamido-2-deoxy-d-galactose and N-acetyl neuraminic acid were invariably present in κ-casein. N-acetyl neuraminic acid was located almost entirely on the glycopeptides whereas the greater proportion of d-mannose was attached to the para-κ-casein. d-Galactose and 2-acetamido-2-deoxy-d-galactose were detected in both para-κ-casein and the glycopeptides. In the glycopeptides there are usually about 2 molecules of d-galactose to 1 molecule of 2-acetamido-2-deoxy-d-galactose. Carbohydrates are attached to only a proportion of para-κ-casein molecules. Carbohydrates could not be detected in αs- and β-casein.