Figure 2.

(a) Synthesis of bradykinin. The activated form of Hageman factor promotes the conversion of prekallikrein to kallikrein. In rat, both plasma and tissue kallikrein catalyse the formation of bradykinin. In humans, however, plasma kallikrein generates bradykinin using high molecular weight kininogens and tissue kallikrein generates kallidin using low molecular weight kininogens. (b) Basic amino acid sequence of bradykinin and precursors. Arrows designate the peptide bonds cleaved by: 1 kininase-I; 2 angiotensin converting enzyme (kininase-II); 3 neutral endopeptidase; 4 aminopeptidase.