Goldstein J, Matsueda G R, Shaw S Y
Macromolecular Structure, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08540, USA.
Thromb Haemost. 1996 Sep;76(3):429-38.
Chimeric 59D8-SK was designed to confer fibrin-selectivity to streptokinase by fusion of the Fab fragment of anti-fibrin antibody 59D8 to the N-terminus of streptokinase (SK: Ile1-Lys414). It was expressed in a mouse hybridoma cell line and purified by affinity chromatography on a 59D8-antigen column. Chimeric 59D8-SK is a disulfide-linked heterodimer composed of an antibody light chain (Mr 27,000) and a N-glycosylated chimeric heavy chain (M(r) 90,000). The fibrin targeting by 59D8 increased plasma clot lysis by 2-fold, but connecting 59D8 to SK has provided 59D8-SK several unique properties: (i) 59D8-SK activated human Glu-plasminogen with a significant lag period that coincided with limited proteolysis of 59D8-SK similar to that observed for wild-type SK. In a kinetic study, both gave very similar kinetic parameters for the activation of Glu-plasminogen even though 59D8-SK was N-glycosylated in its SK portion; (ii) 59D8-SK was relatively inactive in human plasma, compared to SK, but it became activated in the presence of clots; (iii) 59D8-SK lysed clots slowly but completely whereas SK lysed clots rapidly but incompletely. Even though the mechanism behind these new properties is not fully understood, they are characteristics of a second-generation plasminogen activator.
嵌合蛋白59D8-SK的设计是通过将抗纤维蛋白抗体59D8的Fab片段融合到链激酶（SK：Ile1-Lys414）的N端，使链激酶具有纤维蛋白选择性。它在小鼠杂交瘤细胞系中表达，并通过59D8抗原柱上的亲和层析进行纯化。嵌合蛋白59D8-SK是一种由抗体轻链（分子量27,000）和N-糖基化嵌合重链（分子量90,000）组成的二硫键连接的异二聚体。59D8对纤维蛋白的靶向作用使血浆凝块溶解增加了2倍，但将59D8连接到SK上赋予了59D8-SK一些独特的特性：（i）59D8-SK激活人Glu-纤溶酶原时存在明显的延迟期，这与59D8-SK的有限蛋白水解相一致，类似于野生型SK的情况。在一项动力学研究中，尽管59D8-SK的SK部分进行了N-糖基化，但两者在激活Glu-纤溶酶原时给出了非常相似的动力学参数；（ii）与SK相比，59D8-SK在人血浆中相对无活性，但在有凝块存在时会被激活；（iii）59D8-SK缓慢但完全地溶解凝块，而SK快速但不完全地溶解凝块。尽管这些新特性背后的机制尚未完全了解，但它们是第二代纤溶酶原激活剂的特征。
