Kinetics of reciprocal pro-urokinase/plasminogen activation - Stimulation by a template formed by the urokinase receptor bound to poly(D-lysine)
Kinetics of reciprocal pro-urokinase/plasminogen activation - Stimulation by a template formed by the urokinase receptor bound to poly(D-lysine)
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DOI：
10.1111/j.1432-1033.1997.00316.x
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发表时间：
1997-04-15
期刊：
影响因子：
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通讯作者：
Petersen, LC
中科院分区：
文献类型：
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作者：
Petersen, LC
纤溶酶原和前尿激酶纤溶酶原激活物（pro-uPA）这两种酶原构成相互激活的系统，因为由uPA催化的纤溶酶原激活产生的纤溶酶可以将pro-uPA激活为uPA。两种这样的酶原，当混合时，将经历自催化、相互激活，导致蛋白水解活性的产生。作为相互酶原激活的一个例子，纤溶酶原/pro-uPA系统进行了分析的动力学模型，它描述了在活化的酶的进展。该模型详细描述了纤溶酶和uPA的进展曲线。它解释了不同浓度的酶原的影响，也解释了反应混合物中纤溶酶底物和抑制剂的影响。该模型假设无显著酶原活性。然而，它并不排除一个非常低的初始蛋白水解活性，当pro-uPA被完全激活时获得的最大0.01%，可以归因于一个真正的pro-uPA活性。uPA受体（uPAR）与pro-uPA/uPA的结合可能影响相互激活反应的单独步骤，或者它可能诱导显著的pro-uPA活性。为了区分这些可能性，研究了重组可溶性（残基1-277）形式的uPAR，uPAR-（1-277）-肽对相互的pro-uPA/纤溶酶原激活的影响。uPAR-（1-277）-肽减弱了酶原的相互激活，结果表明这是由于pro-uPA/uPAR-（1-277）-肽复合物对纤溶酶激活的可及性降低。uPAR-（1-277）-肽在聚（D-赖氨酸）的存在下，引起20倍的相互酶原激活增强。对单独活化步骤的动力学分析表明，这是由于uPA/uPAR-（1-277）-肽对纤溶酶原活化的三倍刺激与前uPA/uPAR-（1-277）-肽对纤溶酶活化的六倍刺激相结合。结果表明，聚D-赖氨酸为纤溶酶原/纤溶酶和uPAR-（1-277）-肽复合物与pro-uPA/uPA之间的催化有利的相互作用提供了模板。没有迹象表明uPAR（1-277）-肽诱导的pro-uPA活性显著增强。
The two zymogens, plasminogen and pra-urokinase plasminogen activator (pro-uPA), constitute a system of reciprocal activation, since plasmin, generated by uPA-catalysed plasminogen activation, can activate pro-uPA to uPA. Two such zymogens, when mixed, will undergo autocatalytic, reciprocal activation resulting in generation of proteolytic activity. As an example of reciprocal zymogen activation, the plasminogen/pro-uPA system was analysed in terms of a kinetic model which describes the progression in activated enzymes. This model gave a detailed description of the progress curves in plasmin and uPA. It accounted for the effects of varying the concentration of the zymogens, and also for the effects of plasmin substrates and inhibitors in the reaction mixture. The model assumes non-significant zymogen activity. It did not, however, exclude that a very low initial proteolytic activity, accounting far maximally 0.01% of that obtained when pro-uPA is fully activated, could be attributed to a genuine pro-uPA activity. Binding of the uPA receptor (uPAR) to pro-uPA/uPA might affect separate steps of the reciprocal activation reaction, or it might induce a significant pro-uPA activity. To distinguish between these possibilities the effect of a recombinant soluble (residues 1-277) form of uPAR, uPAR-(1-277)-peptide, on reciprocal pro-uPA/plasminogen activation was studied. uPAR-(1-277)-peptide attenuated reciprocal zymogen activation, and the results suggested that this was due to a decreased accessibility of the pro-uPA/uPAR-(1-277)-peptide complex to activation by plasmin. The uPAR-(1-277)-peptide in the presence of poly(D-lysine) caused a 20-fold enhancement of reciprocal zymogen activation. Kinetic analysis of separate activation steps revealed that this was due to a threefold stimulation of plasminogen activation by uPA/uPAR-(1-277)-peptide combined with a sixfold stimulation of plasmin's activation of pre-uPA/uPAR-(1-277)-peptide. The results suggested that poly(D-lysine) provided a template for a catalytically favourable interaction between plasminogen/plasmin and the uPAR-(1-277)-peptide complex with pro-uPA/uPA. There was no indication of a significant uPAR(1-277)-peptide-induced enhancement of pro-uPA activity.