Soeda S, Ohki H, Shimeno H, Nagamatsu A
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Fukuoka University, Japan.
Biochim Biophys Acta. 1989 Nov 9;999(1):29-35. doi: 10.1016/0167-4838(89)90025-3.
We have previously demonstrated that the heparin-binding site of plasminogen is located in Val442-plasminogen region (kringle 5 domain plus light (B) chain) (Soeda, S., Kakiki, M., Shimeno, H., and Nagamatsu, A. (1987) Biochim. Biophys. Acta 916, 279-287). The chemical modification of Val442-plasminogen with a lysine reagent, pyridoxal 5'-phosphate (PLP), and sodium borohydride resulted in the incorporation of 8-10 PLP moieties per molecule of the zymogen. This PLP-labeled zymogen had no affinity for a heparin-Sepharose column, whereas the non-labeled one bound to the column. Modification in the presence of heparin decreased the extent of labeling by 1-2 mol of PLP per mol of Val442-plasminogen. To further examine the binding site of plasminogen to heparin, functionally active A and B chains were separated from Lys-plasmin after mild reduction and S-carboxymethylation. Only B chain possessed affinity for heparin-Sepharose. Furthermore, plasmin(ogen) bound to heparin was protected from alpha 2-antiplasmin inhibition. These results indicate that one or two lysine residues located in the catalytic region (B chain) of plasmin(ogen) are essential to heparin binding, and that the binding of plasminogen to heparin or heparin-like substance in extracellular matrix environments may be important for the localization and activation of plasminogen and for the prolongation of the resultant plasmin activity.
我们之前已经证明，纤溶酶原的肝素结合位点位于Val442-纤溶酶原区域（kringle 5结构域加轻链（B链））（Soeda, S., Kakiki, M., Shimeno, H., and Nagamatsu, A. (1987) Biochim. Biophys. Acta 916, 279-287）。用赖氨酸试剂吡哆醛5'-磷酸（PLP）和硼氢化钠对Val442-纤溶酶原进行化学修饰，导致每分子酶原掺入8-10个PLP部分。这种PLP标记的酶原对肝素-琼脂糖柱没有亲和力，而未标记的酶原则与该柱结合。在肝素存在下进行修饰，使每摩尔Val442-纤溶酶原的标记程度降低1-2摩尔PLP。为了进一步研究纤溶酶原与肝素的结合位点，在轻度还原和S-羧甲基化后，从赖氨酸-纤溶酶中分离出功能活性的A链和B链。只有B链对肝素-琼脂糖有亲和力。此外，与肝素结合的纤溶酶（原）受到α2-抗纤溶酶抑制的保护。这些结果表明，位于纤溶酶（原）催化区域（B链）的一个或两个赖氨酸残基对肝素结合至关重要，并且纤溶酶原与细胞外基质环境中的肝素或类肝素物质的结合对于纤溶酶原的定位和激活以及所产生的纤溶酶活性的延长可能很重要。
