Kininogens are inhibitors of thiol proteases. HMW-kininogen plays an important role in blood coagulation by helping to position optimally prekallikrein and factor XI next to factor XII and inhibits the thrombin- and plasmin-induced aggregation of thrombocytes. The active peptide bradykinin that is released from HMW-kininogen shows a variety of physiological effects such as influence in smooth muscle contraction, induction of hypotension, natriuresis and diuresis, etc.