Interaction of one-chain and two-chain tissue plasminogen activator with intact and plasmin-degraded fibrin.
Interaction of one-chain and two-chain tissue plasminogen activator with intact and plasmin-degraded fibrin.
复制标题
单链和双链组织纤溶酶原激活剂与完整和纤溶酶降解的纤维蛋白的相互作用。
作者：
D. Higgins;G. Vehar
组织型纤溶酶原激活剂（T-PA）在体内纤维蛋白溶解中起着核心作用。尽管已知它与纤维蛋白结合，但从未直接测量每摩尔纤维蛋白单体（N）的分离常数（KD）和摩尔数量。在这项研究中，测量了单链形式和重组两链形式的结合，人类T-PA与纤维蛋白的结合。尽管与双链T-PA相比，单链T-PA多于纤维蛋白，但KD和N的纤维蛋白彼此之间的误差。 T-PA明显与用纤维蛋白消化的纤维蛋白原制成的凝块相比，与由完整的纤维蛋白原制成的凝块相比。额外的结合被证明是由于结合位点的新集合与解离常数的形成相比，其分离常数比完整纤维蛋白原制成的凝块上的结合位点更高2-4个数量级。 Epsilon-氨基辅实酸能够竞争完整和降解的纤维蛋白上存在的松散结合位点，但对T-PA与纤溶酶消化形成的新位点的结合几乎没有影响。纤维蛋白介导的纤维蛋白蛋白水解引起的结合增加表明，可以加速纤维蛋白溶解的阳性调节机制。
Tissue-type plasminogen activator (t-PA) plays a central role in fibrinolysis in vivo. Although it is known to bind to fibrin, the dissociation constant (Kd) and number of moles bound per mole of fibrin monomer (n) have never been measured directly. In this study, the binding of both the one-chain form and the two-chain form of recombinant, human t-PA to fibrin was measured. Although more one-chain t-PA than two-chain t-PA is bound to fibrin, the Kd's and n's were within experimental error of each other. Significantly more t-PA is bound to clots made from fibrinogen which has been digested with plasmin than to clots made from intact fibrinogen. The additional binding was shown to be due to the formation of new set(s) of binding site(s) with dissociation constants that are 2-4 orders of magnitude tighter than the binding site present on clots made from intact fibrinogen. epsilon-Aminocaproic acid was capable of competing for the loose binding site present on both intact and degraded fibrin but had little effect on the binding of t-PA to the new site(s) formed by plasmin digestion. This increase in binding caused by plasmin-mediated proteolysis of fibrin suggests a possible mechanism for a positive regulation capable of accelerating fibrinolysis.