Kininogen: Proteins and Enzymes

Kininogen, also known as 2-thiol proteinase inhibitor, is a multi-functional protein. The high molecule weight (HMW) form of kininogen is synthesized as a precursor protein (amino acid residues 1 to 644). The mature chain (residues 19 to 644) is further processed into the heavy chain (residues 19 to 380) and the light chain (residues 390 to 644) with release of the active peptide bradykinin. The heavy chain consists of three cystatin-like domains, which inhibit cysteine proteases. The light chain consists of a His-rich domain, which is associated with clotting activity.