【摘要】 报道了用定住诱变技术，改变无色杆菌蛋白酶Ⅰ的酶原加工位点，使其向左或向右移动，导致突变体成熟酶的肽链从N端延长或缩短若干氨基酸残基．所获突变体显示了低于野生酶的活性．突变体的园二色谱和荧光光谱研究表明，它们的结构发生了某些微小的改变．在不同的pH值、温度和不同浓度的SDS和盐酸胍条件下，也表现了低于天然酶的稳定性．在N端延长的突变体中，酶原加工位点越远离天然加工位点的突变体，显示了越低的活性和稳定性．缩短的突变体活性和稳定性最低．这些结果表明，天然成熟酶的N端可能比较靠近酶的活性中心，并参与构成活性中心附近的局部构象由此可见N端区在成熟酶的结构与功能方面的重要作用．更多还原

【Abstract】 Some APⅠ mutants have been obtained by site-directed mutagenesis. Their processingpositions for changing pro-APⅠ to mature APⅠ were shifted to the left or to the right of the original position of wild type, causing the peptide chains of the mature enzymes of mutants to be extended or to be shortened from their N-termini. Their structures and stabilities were studied byCD and fluorescence spectra etc. in this paper. The obtained results indicated that the structures ofthe enzyme mutants were alternated to some extent, and they also showed stability differencesfrom that of wild type APⅠ under the conditions of different pH values, temperatures and different concentrations of SDS and guanidine chloride. Among the mutants with the extended N-terminus, the farther from the natural processing position was the processing site of a mutant, the loweractivity and stablility it showed. The shortened one has the lowest activity and stability. The results suggested that the N-terminus of natural mature AP Ⅰ might be near from the active site andmake contributions in construction of the local con formation around the active site. It is evidentthat N-terminal region of the mature APⅠ plays an important role in its structure and function.更多还原