Suenson E, Thorsen S
Department of Clinical Chemistry, Rigshospitalet, University of Copenhagen, Denmark.
Biochemistry. 1988 Apr 5;27(7):2435-43. doi: 10.1021/bi00407a029.
Plasmin-catalyzed modification of the native plasma zymogen Glu1-plasminogen to its more reactive Lys78 form has been shown to be enhanced in the presence of fibrin. The aim of the present work has been to characterize the influence of fibrinopeptide release, fibrin polymerization, and plasmin cleavage of fibrin on the rate of Lys78-plasminogen formation. 125I-Labeled Glu1- to Lys78-plasminogen conversion was catalyzed by performed Lys78-plasmin, or by plasmin generated during plasminogen activation with tissue plasminogen activator or urokinase. The two forms of plasminogen were quantitated following separation by polyacrylamide gel electrophoresis in acetic acid/urea. Plasmin generated by plasminogen activator was monitored by a fixed-time amidolytic assay. The rate of Lys78-plasminogen formation was correlated, in separate experiments, to the simultaneous, plasmin-catalyzed cleavage of 125I-labeled fibrinogen or fibrin to fragments X, Y, and D. The radiolabeled components were quantitated after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results show that the formation of both bathroxobin-catalyzed des-A-fibrin and thrombin-catalyzed des-AB-fibrin leads to marked stimulation of Lys78-plasminogen formation, whereas inhibition of fibrin polymerization, with Gly-Pro-Arg-Pro, abolishes the stimulatory effect. The rate of Lys78-plasminogen formation varies markedly in the course of fibrinolysis. The apparent second-order rate constant of the reaction undergoes a transient increase upon transformation of fibrin to des-A(B) fragment X polymer and decreases about 10-fold to the level observed during fibrinogenolysis upon further degradation to soluble fragments Y and D.(ABSTRACT TRUNCATED AT 250 WORDS)
纤溶酶催化天然血浆酶原Glu1-纤溶酶原转变为其反应性更强的Lys78形式，已证实在纤维蛋白存在时会增强。本研究的目的是确定纤维蛋白肽释放、纤维蛋白聚合以及纤溶酶对纤维蛋白的裂解作用对Lys78-纤溶酶原形成速率的影响。用已形成的Lys78-纤溶酶，或用组织纤溶酶原激活剂或尿激酶激活纤溶酶原过程中产生的纤溶酶催化125I标记的Glu1-纤溶酶原向Lys78-纤溶酶原的转化。通过在乙酸/尿素中进行聚丙烯酰胺凝胶电泳分离后，对两种形式的纤溶酶原进行定量。通过固定时间酰胺水解测定法监测纤溶酶原激活剂产生的纤溶酶。在单独的实验中，将Lys78-纤溶酶原形成速率与同时进行的、纤溶酶催化的125I标记的纤维蛋白原或纤维蛋白裂解为片段X、Y和D相关联。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分离后，对放射性标记成分进行定量。结果表明，巴曲酶催化的去A-纤维蛋白和凝血酶催化的去AB-纤维蛋白的形成均导致Lys78-纤溶酶原形成的显著刺激，而用甘氨酰-脯氨酰-精氨酰-脯氨酸抑制纤维蛋白聚合则消除了这种刺激作用。在纤维蛋白溶解过程中，Lys78-纤溶酶原形成速率有显著变化。当纤维蛋白转化为去A（B）片段X聚合物时，反应的表观二级速率常数会短暂增加，而在进一步降解为可溶性片段Y和D时，会降至纤维蛋白原溶解过程中观察到的水平的约十分之一。（摘要截取自250字）
