蚯蚓体内一种纤溶酶原激活剂(e-PA)的部分性质研究

从赤子爱胜蚓（Ｅｉｓｅｎｉａｆａｅｔｉｄａ）中纯化出的一种纤溶酶原激活剂（ｅ－ＰＡ）在纤维蛋白平板上可表现出三种活性，分别记为：ＣＦＰｇ，ｕＣＦＰｇ和ｕＣＦ．为更好了解各种活性与ｅ－ＰＡ的纤溶能力的关系，考察了在ＳＤＳ和不同抑制剂存在下各种活性的变化．结果表明，ＳＤＳ可以增强ＣＦＰｇ活性且使得ｅ－ＰＡ变得对一些抑制剂更敏感；ｌｅｕｐｅｐｔｉｎ，ｃｈｙｍｏｓｔａｔｉｎ，ｐｅｐｓｔａｔｉｎ，ａｐｒｏ－ｔｉｎｉｎ，ｐｈｅｎｙｌｍｅｔｈｙｌｓｕｌｆｏｎｙｌｆｌｕｏｒｉｄｅ（ＰＭＳＦ）和ｄｉｔｈｉｏｔｈｒｅｉｔｏｌ（ＤＴＴ）对ｕＣＦ没有影响；ｐｅｐ－ｓｔａｔｉｎ能增强ＣＦＰｇ和ｕＣＦＰｇ活性，Ｅ－６４（一种巯基抑制剂）能增强ｕＣＦＰｇ和ｕＣＦ活性．这些现象说明不能简单将ｅ－ＰＡ归结为丝氨酸蛋白酶或巯基蛋白酶．此外又以纤溶酶原为底物，分析了ｅ－ＰＡ在体外降解天然蛋白质的肽键特异性，结果表明：ｅ－ＰＡ可以切割碱性氨基酸，小的中性氨基酸及Ｍｅｔ的羧基端，同时ｅ－ＰＡ确能将纤溶酶原切割为纤溶酶；这一结论为ｅ－ＰＡ有可能成为新型溶栓药物提供了生化基础．

Characterization of a Plasminogen Activator from Eisenia faetida

A plasminogen activator from Eisenia faetida (e PA)shows three kinds of fibrinolysis activities on fibrin plates.They are designated as CFPg(complete fibrinolysis in plasminogen rich plate),uCFPg(uncompleted fibrinolysis in plasminogen rich plate)and uCF(uncompleted fibrinolysis in plasminogen free plate).To investigate these different activities,SDS and some inhibitors are used to study their influence on the activities.SDS can activated CFPg and render e PA more sensitive to some inhibitors.Leupeptin,chymostatin,pepstatin,aprotinin,phenylmethylsulfonyl fluoride(PMSF)and dithiothreitol(DTT)have no effect on uCF.Pepstatin can stimulate CFPg and uCFPg while E 64,a kind of thiol inhibitor,can stimulate uCFPg and uCF.All of these results make it more difficult to sort out e PA as a serine protease or a thioprotease.Furthermore,the specificity of peptide bond using plasminogen as substrate is that e PA can cleave the carboxyl side of basic amino acids,small neutral amino acids and Met residue.Specifically,e PA can cleave plasminogen to produce plasmin,which is the biochemical base for e PA's use for thrombolysis.