Critical protein involved in assembly of the contact system on cell membranes. HK is found in platelets, granulocytes, and endothelial cells and is a substrate for kallikrein. Cleavage by kallikrein releases bradykinin, a bioactive peptide that contributes to vessel patency. HK functions as an antithrombotic (inhibits thrombin-induced platelet activation), antiadhesive (prevents adhesion of neutrophils to artificial surfaces), and profibrinolytic (allows binding of prekallikrein and its activation. The slide show entitled Coagulation Pathways (All Components) shows how HK relates to the other coagulation factors. See also the slide show entitled Intrinsic Pathway-APTT.
