Aritomi M, Watanabe N, Ohishi R, Gomi K, Kiyota T, Yamamoto S, Ishida T, Maruyama I
Institute for Life Science Research, Asahi Chemical Industry, Fuji City, Japan.
Thromb Haemost. 1993 Sep 1;70(3):418-22.
Recombinant human soluble thrombomodulin (rhs-TM), having no transmembrane domain or chondroitin sulfate, was expressed in Chinese hamster ovary cells. Interactions between rhs-TM, thrombin (Th), protein C (PC) and antithrombin III (ATIII) were studied. Equilibrium between rhs-TM and Th had no detectable time lag in clotting inhibition (Kd = 2.6 nM) or PC activation (Kd = 22 nM), while ATIII inhibited Th at a bimolecular rate constant = 5,200 M-1s-1 (Kd < 0.2 nM). A mixture of ATIII, Th and rhs-TM showed that ATIII reacted with Th slower than rhs-TM, whose presence did not affect the reaction between ATIII and Th. In a mixture of rhs-TM, ATIII and PC, the repeated addition of Th caused the repeated activation of PC; which was consistent with the simulation based on the assumption that rhs-TM is recycled as a Th cofactor. From these results, we concluded that upon inhibition of the rhs-TM-Th complex by ATIII, rhs-TM is released to recombine with free Th and begins to activate PC, while the Th-ATIII complex does not affect rhs-TM-Th equilibrium.
重组人可溶性血栓调节蛋白（rhs-TM），无跨膜结构域或硫酸软骨素，在中国仓鼠卵巢细胞中表达。研究了rhs-TM、凝血酶（Th）、蛋白C（PC）和抗凝血酶III（ATIII）之间的相互作用。rhs-TM与Th之间的平衡在凝血抑制（Kd = 2.6 nM）或PC激活（Kd = 22 nM）方面没有可检测到的时间滞后，而ATIII以双分子速率常数= 5200 M-1s-1抑制Th（Kd < 0.2 nM）。ATIII、Th和rhs-TM的混合物表明，ATIII与Th的反应比rhs-TM慢，rhs-TM的存在不影响ATIII与Th之间的反应。在rhs-TM、ATIII和PC的混合物中，重复添加Th会导致PC的重复激活；这与基于rhs-TM作为Th辅因子被循环利用这一假设的模拟结果一致。从这些结果中，我们得出结论，当ATIII抑制rhs-TM-Th复合物时，rhs-TM被释放以与游离的Th重新结合并开始激活PC，而Th-ATIII复合物不影响rhs-TM-Th平衡。
