Song A, Liu J N, Yu R R, Cui D F, Zhou T M, Cui H R, Zhu D X
Department of Biochemistry, Nanjing University, PRC.
Sci China B. 1992 Aug;35(8):966-73.
In view of the similarity of the charge distribution between fibrin A alpha 148-161 and A chain 149-157 of urokinase, the latter might compete with fibrin A alpha 148-161 when single chain pro-urokinase is converted to double chain urokinase. To test this, the stretch of urokinase A chain 135-157 was separated from the low molecular weight urokinase, a competitive binding between this stretch and fibrin to tPA kringle-2 was shown by radio-binding assay. The inhibition of the stretch on the fibrin stimulated activation of plasminogen was demonstrated in the caseinolytic system. The synthesized novapeptide urokinase A chain 149-157 (R-peptide) showed a significant inhibition on the activation of plasminogen in the presence of fibrin. By contrasting finely with R-peptide, a synthesized novapeptide in which Arg154 and Arg156 were replaced by Asp (D-peptide) did not show any inhibition effect on the fibrin stimulated activation of plasminogen by tPA. These results suggest that the positively charged residues in the stretch 149-157 of urokinase are crucial for the inhibition of fibrin binding with the kringle domain of urokinase.
鉴于纤维蛋白Aα148 - 161与尿激酶A链149 - 157之间电荷分布的相似性，当单链尿激酶原转化为双链尿激酶时，后者可能会与纤维蛋白Aα148 - 161竞争。为了验证这一点，将尿激酶A链135 - 157片段从低分子量尿激酶中分离出来，通过放射结合试验表明该片段与纤维蛋白对组织型纤溶酶原激活物kringle - 2存在竞争性结合。在酪蛋白溶解系统中证实了该片段对纤维蛋白刺激的纤溶酶原激活具有抑制作用。合成的九肽尿激酶A链149 - 157（R - 肽）在有纤维蛋白存在的情况下对纤溶酶原的激活表现出显著抑制作用。与R - 肽形成鲜明对比的是，一种将Arg154和Arg156替换为Asp的合成九肽（D - 肽）对组织型纤溶酶原激活物介导的纤维蛋白刺激的纤溶酶原激活没有任何抑制作用。这些结果表明，尿激酶149 - 157片段中的带正电荷残基对于抑制纤维蛋白与尿激酶kringle结构域的结合至关重要。
