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以前认为血浆中抗纤溶酶(anti-plasmin,AP)主要有α_2-巨球蛋白(α_2-MG)和α_1-抗胰蛋白酶(α_1-AT)。1976～1977年从血浆分离出α_2-抗纤溶酶(α_2-AP)。它是血浆中主要抗纤溶物质。近年在日本、荷兰、美国发现3例有严重出血症状的遗传性α_2-AP缺乏症,证实了纤溶抑制物在保护血凝块不被溶解以维持止血机制中的重要作用。纤溶酶形成后立即与α_2-AP结合。当大部分纤溶酶原(PG)被激活,饱和了α_2-AP之后,过多的纤溶酶才被α_2-MG灭活。至于α_1-AT,除非加入外源纤溶酶,否则不与血浆中纤溶酶发生作用。在纯系统中,抑制纤溶酶作用的血浆成分尚有内-α-抗胰蛋白酶(inter-α-AT)、抗凝血酶Ⅲ-肝素复合物及C_1-酯酶抑制物。
Plasma anti-plasmin (α-2-MG) and α 1-antitrypsin (α 1 -AT) were previously thought to be the major anti-plasmin molecules in plasma. From 1976 to 1977, α_2-anti-plasmin (α_2-AP) was isolated from plasma. It is the main anti-fibrinolytic substance in blood plasma. In recent years in Japan, the Netherlands and the United States, 3 cases of hereditary α_2-AP deficiency with severe bleeding symptoms were found, demonstrating the important role of fibrinolysis inhibitors in protecting blood clots from being dissolved to maintain the hemostatic mechanism. Plasmin is bound to α_2-AP immediately after its formation. When most of the plasminogen (PG) is activated, the excess of plasmin is inactivated by α_2-MG after saturation of α_2-AP. As for the α_1-AT, plasminogen is not involved in the plasma unless an exogenous plasmin is added. In pure systems, plasmin that inhibits plasmin also has inter-α-AT, antithrombin Ⅲ-heparin complexes, and C 1-esterase inhibitors.