Jörg M, Binder B R
Thromb Res. 1985 Aug 1;39(3):323-31. doi: 10.1016/0049-3848(85)90228-2.
Kinetics of plasminogen activation by purified activated plasma kallikrein have been studied in a purified system using Glu-plasminogen as a substrate. A synthetic paranitroanilide substrate was used for quantification of the formed plasmin. In that system kallikrein cleaved plasminogen with a Km value of 0.56 microM, a kcat of 1.6 X 10(-4) s-1 and a catalytic efficiency kcat/Km of 2.7 X 10(-4) s-1 microM-1. Addition of CNBr fibrinogen fragments resulted in an increase of Km to 1.18 microM, an increase of kcat to 5.1 X 10(-4) s-1 and an increase in the catalytic rate constant kcat/Km to 4.3 X 10(-4) s-1 microM-1. Addition of purified high molecular weight kininogen had no effect on the kinetics of plasminogen activation whether or not stimulating fibrinogen fragments were present. A stimulating effect of fibrinogen fragments could also be shown for the cleavage of the low molecular weight paranitroanilide substrate H-D-Pro-Phe-Arg-pNA by kallikrein; in that system the kcat for substrate cleavage by kallikrein increased from 200 s-1 to 280 s-1, while the Km value remained unchanged. From these data it can be concluded that based on enzyme kinetic studies plasminogen activator activity of purified plasma kallikrein is about 1/1000 of that of high molecular weight urokinase and is only slightly influenced by addition of stimulating fibrinogen fragments. Addition of high molecular weight kininogen does not affect plasminogen activator activity of purified plasma kallikrein.
在一个以Glu - 纤溶酶原为底物的纯化系统中，研究了纯化的活化血浆激肽释放酶激活纤溶酶原的动力学。使用一种合成的对硝基苯胺底物来定量生成的纤溶酶。在该系统中，激肽释放酶裂解纤溶酶原时，Km值为0.56微摩尔，kcat为1.6×10⁻⁴秒⁻¹，催化效率kcat/Km为2.7×10⁻⁴秒⁻¹微摩尔⁻¹。添加CNBr纤维蛋白原片段导致Km增加至1.18微摩尔，kcat增加至5.1×10⁻⁴秒⁻¹，催化速率常数kcat/Km增加至4.3×10⁻⁴秒⁻¹微摩尔⁻¹。无论是否存在刺激纤维蛋白原片段，添加纯化的高分子量激肽原对纤溶酶原激活的动力学均无影响。激肽释放酶对低分子量对硝基苯胺底物H - D - Pro - Phe - Arg - pNA的裂解也可显示出纤维蛋白原片段的刺激作用；在该系统中，激肽释放酶裂解底物的kcat从200秒⁻¹增加至280秒⁻¹，而Km值保持不变。从这些数据可以得出结论，基于酶动力学研究，纯化的血浆激肽释放酶的纤溶酶原激活剂活性约为高分子量尿激酶的1/1000，并且仅受到刺激纤维蛋白原片段添加的轻微影响。添加高分子量激肽原不会影响纯化的血浆激肽释放酶的纤溶酶原激活剂活性。
