蚯蚓纤溶酶原激活剂(e-PA)小亚基活性中心的酶学性质及CD光谱的研究

蚯蚓纤溶酶原激活剂（ｅ－ＰＡ）具有多种底物特异性．对构成其的小亚基的活性中心的研究有利于阐述ｅ－ＰＡ的结构与功能的关系．利用胰蛋白酶的特异性抑制剂ＴＬＣＫ（Ｎ－α－ｐ－ｔｏｓｙｌ－Ｌ－ｌｙｓｉｎｅｃｈｌｏｒｏｍｅｔｈｙｌｋｅｔｏｎｅ）对小亚基进行抑制活性的研究，结果表明ＴＬＣＫ对酶促反应的抑制曲线与可逆抑制曲线相似，但在抑制剂存在下的最大反应速度与抑制剂不存在时的最大反应速度不同．结合小亚基在ＴＬＣＫ存在下的ＣＤ光谱变化，证明了小亚基分子表面存在两个活性位点，这两个活性位点对ＴＬＣＫ的敏感性不同，从而造成ＴＬＣＫ抑制行为的异常．推测不同的活性结构对应于不同的底物特异性．

The Enzymology Properties and the CD Spectra of the Active Centers of the Small Subunit of a Plasminogen Activator from Eisenia fetida (e PA)

A plasminogen activator from Eisenia fetida (e PA) has multiple substrate specificities.The knowledge on the active center of its subunits is important to understand the relationship between the function and the structure of e PA.Using TLCK,a specific trypsin inhibitor,the active centers were studied.There appeared reversible inhibition with TLCK,although the Vmax with TLCK,0 445 μmol·L -1 ·s -1 ,was smaller than that without TLCK,0 65 μmol·L -1 ·s -1 .It was confirmed by the difference of CD spectra under different concentrations of TLCK that there were two kinds of active centers,which had different sensitivities to TLCK,and were responsible for different substrate specificities.