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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．
One of the plasminogen activators (e-PA) purified from Eiseniafaetida showed three activities on the fibrin plate, denoted as CFPg, uCFPg and uCF, respectively. To better understand the relationship between various activities and fibrinolytic ability of e-PA, various changes in activity in the presence of SDS and various inhibitors were examined. The results showed that SDS could enhance CFPg activity and make e-PA more sensitive to some inhibitors; leupeptin, chymostatin, pepstatin, apro-tin, phenylmethylsulfonylfluoride (PMSF) and dithiothreitol Enhancing CFPg and uCFPg activity, E-64, a sulfhydryl inhibitor, enhances uCFPg and uCF activity. These phenomena suggest that e-PA can not simply be reduced to serine protease or thiol protease. In addition, plasminogen was used as a substrate to analyze the peptide bond specificity of e-PA degradation of native protein in vitro. The results showed that e-PA can cleave basic amino acids, small neutral amino acids and the carboxyl end of Met, At the same time, e-PA was able to cleave plasminogen into plasmin; this conclusion provides e-PA with the potential to become a biochemical basis for novel thrombolytic drugs.