Localisation and importance of the sugar part of human casein.

The study of glycopeptides obtained after enzymic digestions of human caseinoglycopeptide demonstrated the presence of several (up to 10) prosthetic sugar groups distributed throughout the peptide chain instead of only one in the case of cow and sheep kappa-caseinoglycopeptides. One of the glycopeptides allowed us to complete the C-terminal sequence of human caseinoglycopeptide previously published in part by others. The predicted secondary structure was in accordance with the high number of sugar groups situated all but one in beta-turns. A significant microheterogeneity seems to occur at the sugar level of human caseinoglycopeptide, which might thus present differences from one milk to another.