Plasma inhibitors of the components of the fibrinolytic pathway in man

The effect of highly purified inhibitor of the first component of complement (CāINH), alpha2 macroglobulin (alpha2M), and alpha1 antitrypsin on the components of the fibrinolytic pathway in human plasma has been examined. CāINH was the only factor active upon the Hageman factor fragments functioning at the initial step of the fibrinolytic pathway, alpha2M was the only factor active against the plasminogen activator and the most active inhibitor of plasmin. The inhibition of plasmin by alpha2M appeared stoichiometric with one molecule of alpha2M inhibiting two molecules of plasmin. All three plasma inhibitors were active against plasmin.