Identification of C-terminal peptides of bovine beta-casein that enhance proliferation of rat lymphocytes.

A casein polypeptidic fraction, obtained from a pepsin-chymosin digestion of caseins, showed a mitogenic effect on primed lymph node (LN) cells and unprimed spleen cells of rats. A biologically active C-terminal sequence of bovine beta-casein (residues 192-209) was characterized. The corresponding synthetic peptide had a stimulatory effect on primed LN cells but failed to enhance proliferation of spleen cells. We prepared two chymosin digests (PA and PB) of bovine beta-casein which contained, respectively, 80% and 95% of the sequence including residues 193-209. They induced a significant proliferative response in both LN and spleen cells. It is therefore possible that other active peptides in the PA preparation may be involved in mitogenic activity.