Jakubowski H V, Owen W G
Department of Biochemistry, University of Iowa, Iowa City 52242.
J Biol Chem. 1989 Jul 5;264(19):11117-21.
The endothelial cell surface membrane protein thrombomodulin binds thrombin with high affinity and acts as both a cofactor for protein C activation and an inhibitor of fibrinogen hydrolysis. We have previously shown that bovine thrombomodulin is a competitive inhibitor of fibrinogen binding to thrombin but has no effect on thrombin activity toward tripeptide substrates or antithrombin III. Hence, thrombomodulin and fibrinogen may share macromolecular specificity sites on thrombin which are distinct from the active site. In this investigation, we have studied the interaction of thrombin-thrombomodulin with fibrinogen and various thrombin derivatives. We show that fibrinogen is a competitive inhibitor of thrombomodulin binding to thrombin, with a Kis = 10 microM. Thrombin derivatives (bovine (pyridoxal phosphate)4-thrombin and human thrombin Quick I), which bind fibrinogen with much reduced affinity, are shown to also interact with thrombomodulin with greatly reduced affinity. These results are consistent with the hypothesis that thrombomodulin and fibrinogen share macromolecular specificity sites on thrombin.
内皮细胞表面膜蛋白血栓调节蛋白以高亲和力结合凝血酶，既是蛋白C活化的辅因子，也是纤维蛋白原水解的抑制剂。我们之前已经表明，牛血栓调节蛋白是纤维蛋白原结合凝血酶的竞争性抑制剂，但对凝血酶对三肽底物或抗凝血酶III的活性没有影响。因此，血栓调节蛋白和纤维蛋白原可能在凝血酶上共享与活性位点不同的大分子特异性位点。在本研究中，我们研究了凝血酶-血栓调节蛋白与纤维蛋白原及各种凝血酶衍生物的相互作用。我们发现纤维蛋白原是血栓调节蛋白结合凝血酶的竞争性抑制剂，Kis = 10 microM。与纤维蛋白原结合亲和力大大降低的凝血酶衍生物（牛（磷酸吡哆醛）4-凝血酶和人凝血酶Quick I），也显示与血栓调节蛋白的相互作用亲和力大大降低。这些结果与血栓调节蛋白和纤维蛋白原在凝血酶上共享大分子特异性位点的假设一致。
