Wu H L, Chang B I, Wu D H, Chang L C, Gong C C, Lou K L, Shi G Y
Biochemistry Department, Medical College, National Cheng-Kung University, Tainan, Taiwan Republic of China.
J Biol Chem. 1990 Nov 15;265(32):19658-64.
Glu1-, Lys77-, miniplasminogens, kringle 1-3, kringle 1-5A, and kringle 1-5R were able to bind with fibrin, while microplasminogen and kringle 4 did not bind significantly. Kringle 1-5A, but not kringle 1-3, effectively inhibited the binding of Glu1-, Lys77-, and miniplasminogens with fibrin. Miniplasminogen also inhibited the binding of Glu1-plasminogen with fibrin. The binding of kringle 1-3 with fibrin was blocked by mini- or Glu1-plasminogen. It is therefore evident that there are two fibrin-binding domains in plasminogen and that the one in kringle 5 is of higher affinity than that in kringle 1-3. CNBr cleavage products of fibrinogen effectively enhanced the activation of Glu1-, Lys77-, or miniplasminogens, but not microplasminogen, by tissue-type plasminogen activator. Kringle 1-5, but not kringle 1-3, dose-dependently inhibited the enhancement by fibrinogen degradation products of Glu1-plasminogen activation by the activator. Lysine and epsilon-aminocaproic acid could inhibit the binding of plasminogens and plasminogen derivatives with fibrin and block the enhancement effect of fibrinogen degradation products on plasminogen activation. The data clearly illustrate that the binding of plasminogen with fibrin, mainly determined by kringle 5, is essential for effective activation by tissue-type plasminogen activator. However, the presence of kringle 1-4 in the plasminogen molecule is required for the full enhancing effect since the kcat/Km of miniplasminogen activation in the presence of fibrinogen degradation products was 8.2 microM-1 min-1 which is significantly less than 52.0 microM-1 min-1 of Glu1-plasminogen.
谷氨酸-1、赖氨酸-77、微型纤溶酶原、kringle 1-3、kringle 1-5A和kringle 1-5R能够与纤维蛋白结合，而微纤溶酶原和kringle 4则无明显结合。Kringle 1-5A而非kringle 1-3能有效抑制谷氨酸-1、赖氨酸-77和微型纤溶酶原与纤维蛋白的结合。微型纤溶酶原也能抑制谷氨酸-1纤溶酶原与纤维蛋白的结合。kringle 1-3与纤维蛋白的结合被微型或谷氨酸-1纤溶酶原阻断。因此，很明显纤溶酶原中有两个纤维蛋白结合结构域，且kringle 5中的结合结构域比kringle 1-3中的具有更高的亲和力。纤维蛋白原的溴化氰裂解产物能有效增强组织型纤溶酶原激活剂对谷氨酸-1、赖氨酸-77或微型纤溶酶原的激活作用，但对微纤溶酶原无效。Kringle 1-5而非kringle 1-3能剂量依赖性地抑制纤维蛋白原降解产物对激活剂激活谷氨酸-1纤溶酶原的增强作用。赖氨酸和ε-氨基己酸能抑制纤溶酶原及纤溶酶原衍生物与纤维蛋白的结合，并阻断纤维蛋白原降解产物对纤溶酶原激活的增强作用。这些数据清楚地表明，主要由kringle 5决定的纤溶酶原与纤维蛋白的结合对于组织型纤溶酶原激活剂的有效激活至关重要。然而，纤溶酶原分子中kringle 1-4的存在对于充分增强作用是必需的，因为在存在纤维蛋白原降解产物的情况下，微型纤溶酶原激活的kcat/Km为8.2 μM-1 min-1，显著低于谷氨酸-1纤溶酶原的52.0 μM-1 min-1。
