Christensen U, Müllertz S
Biochim Biophys Acta. 1977 Jan 11;480(1):275-81. doi: 10.1016/0005-2744(77)90340-0.
A method for determining initial velocities of the urokinase (EC 3.4.99.26) catalysed converstion of NH2-terminal lysine plasminogen to plasmin (EC 3.4.21.7) is presented. This reaction has been coupled with the hydrolysis of alpha-N-benzyoly-L-arginine ethyl ester, which is catalysed by plasmin, and its rate has been determined from the time course of the overall reaction. The proenzyme-enzyme conversion was found to obey the Michaelis-Menten rate equation. The following values of the kinetic parameters were obtained: the apparent Michaelis constant, Km = 40.7 +/- 6.2 muM; the catalytic constant, kc = 2.59+/-0.31 s(-1), and kc/Km = 6.36-10(4) +/- 0.24-10(4) M(-1)-s(-1).
本文介绍了一种测定尿激酶（EC 3.4.99.26）催化NH2末端赖氨酸纤溶酶原转化为纤溶酶（EC 3.4.21.7）初始速度的方法。该反应与纤溶酶催化的α-N-苄氧羰基-L-精氨酸乙酯水解反应偶联，并根据总反应的时间进程确定其速率。发现酶原-酶转化遵循米氏速率方程。获得了以下动力学参数值：表观米氏常数Km = 40.7 +/- 6.2 μM；催化常数kc = 2.59 +/- 0.31 s(-1)，以及kc/Km = 6.36×10(4) +/- 0.24×10(4) M(-1)-s(-1)。
