The bradykinin (BK) fragment (1-5) (RPPGF) is among the most stable of naturally occurring metabolites. It may be used as a marker for BK production in vivo. It is known that an intact Arg residue in the C-terminus is required for biological activities. BK 1-5 is the minimal peptide that inhibited α-thrombin-induced platelet aggregation and secretion and calcium mobilization. It also prevented α-thrombin from cleaving the thrombin receptor peptide, NATLDPRSFLLR, between arginine and serine. Such antithrombin activities of BK 1-5 may contribute to the cardioprotective nature of kinins.
