Aprotinin formed by certain chemical proportion reversible enzyme - inhibitor complex and thus inhibit human trypsin, plasmin, plasma and tissue kallikrein. The the serine active protease in vascular soothing hormone - bradykinin original - kinin system, complement system, coagulation system plays a major role, plasmin and plasma kallikrein plays a key role in these systems.
Aprotinin is formed through the active part of the enzyme serine, aprotinin - proteasome complex to achieve the inhibitory effect. However, with a different protease binding, shows a different dissociation constant. The most solid combination with trypsin (Ki = 0.06nmoN), this constant is one of the lowest protein interactions reported (Laydunski et al.1974). The combination of human plasminogen is not very solid. Because the larger the K value of the enzyme - inhibitor complex (Ki = 1 nmon), PI3 peptidase inhibitor 3, skin-derived may therefore is reversible (Wimann, 1980), and human plasma blood vessels to relieve binding complexes rather weak (Ki = 30nmol / L) , but still aprotinin within the therapeutic range (Nakahara, 1983).
Aprotinin not only in combination with the free enzyme molecules, and can be combined with the bound enzyme and a third component (if there binding ability of the enzyme active center). Therefore free of plasmin, PI3 peptidase inhibitor 3, skin-derived aprotinin inhibition also inhibit the intermediates formed in the thrombolysis with streptokinase - plasmin streptokinase complex (Wimann, 1980).
Antifibrinolytic effect of aprotinin is based on the inhibition of the proteolytic activation of plasminogen, unlike synthetic anti-fibrinolytic agent, due to the direct inhibition of the excessive activation of plasminogen, aprotinin, not only to protect the direct bottom material (fibrin)PI3 peptidase inhibitor 3, skin-derived are not plasmin degradation and protecting the fibrinogen in the plasma in the v VIII factor and serum α2-globulin.