Watahiki Y, Takada Y, Takada A
Thromb Res. 1987 Apr 1;46(1):9-18. doi: 10.1016/0049-3848(87)90202-7.
The kinetics of the activation of Glu-plasminogen (Glu-plg) and Lys-plasminogen (Lys-plg) by urokinase (UK) were studied in purified systems. The activation of plasminogen by UK in the purified systems followed Michaelis-Menten kinetics with a Michaelis constant (Km) of 1.45 microM and a catalytic rate constant (kcat) of 0.93/sec for Glu-plg as compared to 0.25 microM (Km) and 0.82/sec (kcat) for Lys-plg. In the presence of fibrin and fibrinogen or its plasmin degradation products (fragment D and fragment E), Km for Glu-plg hardly changed, whereas kcat for Glu-plg increased. Effect on increase in kcat was in the order of fibrin greater than fibrinogen greater than D greater than E. Fibrin, fibrinogen, D and E did not influence the activation of Lys-plg by UK. These results indicate that Glu-plg bound to fibrin, fibrinogen, D or E becomes easily activatable by UK. The activation of Lys-plg, however, is not influenced in the presence of fibrin, fibrinogen, D or E.
在纯化系统中研究了尿激酶（UK）激活谷氨酸纤溶酶原（Glu - plg）和赖氨酸纤溶酶原（Lys - plg）的动力学。在纯化系统中，UK激活纤溶酶原遵循米氏动力学，Glu - plg的米氏常数（Km）为1.45微摩尔，催化速率常数（kcat）为0.93/秒，而Lys - plg的Km为0.25微摩尔，kcat为0.82/秒。在存在纤维蛋白、纤维蛋白原或其纤溶酶降解产物（片段D和片段E）的情况下，Glu - plg的Km几乎不变，而Glu - plg的kcat增加。对kcat增加的影响顺序为纤维蛋白大于纤维蛋白原大于D大于E。纤维蛋白、纤维蛋白原、D和E不影响UK对Lys - plg的激活。这些结果表明，与纤维蛋白、纤维蛋白原、D或E结合的Glu - plg很容易被UK激活。然而，在存在纤维蛋白、纤维蛋白原、D或E的情况下，Lys - plg的激活不受影响。
