Urano T, Sator de Serrano V, Gaffney P J, Castellino F J
Department of Chemistry, University of Notre Dame, Indiana 46556.
Biochemistry. 1988 Aug 23;27(17):6522-8. doi: 10.1021/bi00417a049.
The activation of human [Glu1]plasminogen [( Glu1]Pg) by human recombinant (rec) two-chain tissue plasminogen activator (t-PA) is inhibited by Cl-, at physiological concentrations, and stimulated by epsilon-aminocaproic acid (EACA), as well as fibrin(ogen). Chloride functions as a result of its binding to [Glu1]Pg, with a Ki of approximately 9.0 mM, thereby rendering [Glu1]Pg a less effective substrate for two-chain rec-t-PA. EACA stimulates the activation in Cl-(-)containing solutions, with a Ka of approximately 4.0 mM, primarily by reversal of the Cl-(-)inhibitory effect. Fibrinogen appears to exert its stimulatory properties mainly through effects on the enzyme, two-chain rec-t-PA, with a Ka of approximately 3.7 microM in activation systems containing physiological levels of Cl-. Analysis of the results of this paper reveals that normal plasma components, Cl- and fibrinogen, exert major regulatory roles on the ability of [Glu1]Pg to be activated by two-chain rec-t-PA, in in vitro systems. The presence of Cl- inhibits the stimulation of [Glu1]Pg activation that would normally occur in the presence of fibrinogen, a result of possible importance to the observation that some degree of systemic fibrinogenolysis accompanies therapeutic use of tissue plasminogen activator.
在生理浓度下，氯离子（Cl⁻）可抑制人重组双链组织型纤溶酶原激活剂（t-PA）对人[Glu1]纤溶酶原[（Glu1）Pg]的激活作用，而ε-氨基己酸（EACA）以及纤维蛋白（原）则可刺激该激活作用。氯离子发挥作用是因其与[Glu1]Pg结合，解离常数（Ki）约为9.0 mM，从而使[Glu1]Pg成为双链重组t-PA的一种效果较差的底物。EACA在含Cl⁻的溶液中刺激激活作用，解离常数（Ka）约为4.0 mM，主要是通过逆转Cl⁻的抑制作用。在含有生理水平Cl⁻的激活系统中，纤维蛋白原似乎主要通过对酶（双链重组t-PA）的作用发挥其刺激特性，解离常数（Ka）约为3.7 μM。本文结果分析表明，在体外系统中，正常血浆成分Cl⁻和纤维蛋白原对[Glu1]Pg被双链重组t-PA激活的能力发挥主要调节作用。Cl⁻的存在抑制了通常在纤维蛋白原存在时会发生的[Glu1]Pg激活刺激作用，这一结果对于观察到组织型纤溶酶原激活剂治疗使用时伴有一定程度的全身性纤维蛋白原溶解现象可能具有重要意义。
