SHEEP KAPPA-CASEIN PEPTIDES INHIBIT PLATELET-AGGREGATION

The C-terminal part(residues 106-171) of sheep K-casein, called casein oglycopeptide (CGP), inhibits thrombin- and collagen-induced platelet aggregation in a dose-dependent manner (mean inhibitory concentration (IC50) 215 mu M and 100 mu M, respectively). An enzymatic hydrolysate of CGP was fractionated by reverse phase high performance liquid chrom atography: three peptides KDQDK (residues 112-116), TAQVTSTEV (residue s 163-171) and QVTSTEV (residues 165-171) completely inhibited thrombi n-induced platelet aggregation. CGP at a concentration near its IC50 h ad a very long life when incubated in human or guinea-pig plasma. An e x vivo experiment showed that 17% of CGP was found 60 min after its i. v. bolus injection in guinea-pig. By hydrophobic cluster analysis, hum an fibrinogen and sheep K-casein peptides, inhibitors of platelet aggr egation, were compared and we observed similarities for their C-termin al parts and for their short peptides (RGDF and KDQDK).