Bajzár L, Fredenburgh J C, Nesheim M
Department of Medicine, Queen's University, Kingston, Ontario, Canada.
J Biol Chem. 1990 Oct 5;265(28):16948-54.
The effect of human activated protein C (APC) on fibrinolysis was studied in a cell-free system by continuously monitoring the thrombin-induced formation and subsequent tissue-type plasminogen activator-induced degradation of fibrin. In systems comprising dialyzed human plasma, APC shortens the time for lysis to occur in a concentration-dependent, saturable manner. Half-maximal activity occurs at an APC concentration of 10 nM. The effect is mediated by enhanced plasminogen activation and is dependent upon ionized calcium. The effect is lost when plasma adsorbed with barium citrate is utilized in place of unadsorbed plasma. The effect can be reconstituted, however, from components recovered from the barium citrate precipitate. Fractionation of the barium citrate adsorbable proteins with polyethylene glycol (PEG) provides two fractions, one of which is obtained by precipitation at 5% PEG, and the other of which is obtained from the 5% PEG supernatant by further precipitation at 40% PEG. The latter fraction contains Factor X and presumably the other vitamin K-dependent clotting factors. Both of these fractions together, but neither of them alone, fully reconstitute barium-adsorbed plasma, such that APC-enhanced fibrinolysis occurs as in non-adsorbed plasma. These fractions also are sufficient to provide for an APC effect in a system in which purified plasminogen and fibrinogen are used in place of barium citrate-adsorbed plasma. Thus, an effect of APC on tissue-type plasminogen activator-induced fibrinolysis exists which is Ca2(+)-dependent and requires two or more, as yet unidentified, components that can be precipitated from human plasma by barium citrate.
通过持续监测凝血酶诱导的纤维蛋白形成以及随后组织型纤溶酶原激活剂诱导的纤维蛋白降解，在无细胞系统中研究了人活化蛋白C（APC）对纤维蛋白溶解的影响。在包含透析人血浆的系统中，APC以浓度依赖性、可饱和的方式缩短了发生溶解的时间。在APC浓度为10 nM时出现半数最大活性。该效应由增强的纤溶酶原激活介导，并且依赖于离子钙。当使用用柠檬酸钡吸附的血浆代替未吸附的血浆时，该效应消失。然而，该效应可以从柠檬酸钡沉淀物中回收的成分中重建。用聚乙二醇（PEG）对柠檬酸钡可吸附蛋白进行分级分离可得到两个级分，其中一个通过在5% PEG下沉淀获得，另一个通过在40% PEG下进一步沉淀从5% PEG上清液中获得。后一级分含有因子X以及大概其他维生素K依赖性凝血因子。这两个级分一起，但单独任何一个都不能完全重建钡吸附血浆，从而使得APC增强的纤维蛋白溶解如在未吸附血浆中一样发生。这些级分也足以在使用纯化的纤溶酶原和纤维蛋白原代替柠檬酸钡吸附血浆的系统中提供APC效应。因此，存在APC对组织型纤溶酶原激活剂诱导的纤维蛋白溶解的效应，该效应是Ca2(+)依赖性的，并且需要两个或更多个尚未鉴定的成分，这些成分可通过柠檬酸钡从人血浆中沉淀出来。
