title: Control of coagulation and fibrinolysis by plasma proteinase inhibitors.
abstract: The control of coagulation and fibrinolytic events appears to be primarily due to four plasma proteinase inhibitors, antithrombin III, C-1-esterase inhibitor, alpha-2-antiplasmin, and alpha-2-macroglobulin. Results to date indicate that antithrombin III controls the activity of both thrombin and Factor Xa, C-1-esterase inhibitor controls kallikrein and probably activated Hageman Factor (Factor XIIa), and alpha-2-antiplasmin controls plasmin activity. The role of alpha-2-macroglobulin is not clear since it does not appear to be a primary inhibitor of any of the above enzymes. However, it is probable that it serves two functions, first as a "transfer" agent for the rapid removal of proteinases from the circulation which have been first bound by antithrombin III, C-1-esterase inhibitor, or alpha-2-antiplasmin. The second function is probably that of a back-up inhibitor when the levels of the three important controlling plasma proteins become low. The role of other plasma inhibitors such as alpha-1-proteinase inhibitor, alpha-1-antichymotrypsin, and the inter-alpha-trypsin inhibitor in coagulation and fibrinolysis would appear to be minor since these proteins either do not inactivate enzymes involved in these systems or do so at a rate too slow to be of biological significance.
mesh_terms: D000933:Antifibrinolytic Agents / Q000378:metabolism; D000991:Antithrombins / Q000378:metabolism; D001777:Blood Coagulation / Q000187:drug effects*; D003174:Complement C1 Inactivator Proteins / Q000378:metabolism; D005342:Fibrinolysis / Q000187:drug effects*; D006801:Humans; D011480:Protease Inhibitors / Q000494:pharmacology*; D000511:alpha-Macroglobulins / Q000378:metabolism
chemical_list: D000933:Antifibrinolytic Agents; D000991:Antithrombins; D003174:Complement C1 Inactivator Proteins; D011480:Protease Inhibitors; D000511:alpha-Macroglobulins