The effect of highly purified inhibitor of the first component of complement (CāINH), α2 macroglobulin (α2M), and α1 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, α2M was the only factor active against the plasminogen activator and the most active inhibitor of plasmin. The inhibition of plasmin by α2M appeared stoichiometric with one molecule of α2M inhibiting two molecules of plasmin. All three plasma inhibitors were active against plasmin.
Alan D. Schreiber, Allen P. Kaplan, K. Frank Austen