Occurrence of Leu-Lys-bradykinin and histidine-rich peptide in high-molecular-weight kininogen isolated from horse plasma.

On incubation of purified horse plasma high-molecular-weight kininogen with purified plasma kallikrein, three new peptides, named fragment 1.2, fragment 1 and fragment 2, were released, in addition to the vasopeptide, bradykinin. Fragment 2 contained an extremely high level of histidine, in which eleven residues out of the total 48 residues were characterized. Thus the result proves the existence of the histidine-rich region in horse high-molecular-weight kininogen, which is similar to the region previously identified in bovine high-molecular-weight kininogen. Moreover, we have identified a new kinin derivative, Leu-Lys-bradykinin, in horse high-molecular-weight kininogen.