锰或镍离子取代的氨基酰化酶性质的研究  

Study on properties of Mn^(2+) or Ni^(2+)substituted aminoacylase

作　　者：张英侠[1] 胡凌云[1] 王希成[2] 张彤[2] 周海梦[2] 

机构地区：[1]首都医学院基础部 [2]清华大学生物科学与技术系

出　　处：《清华大学学报（自然科学版）》1993年第6期85-90,共6页Journal of Tsinghua University(Science and Technology)

摘　　要：Ｎ－ａｃｙｌａｍｉｎｏａｃｉｄ ａｍｉｄｏ ｈｙｄｒｏｌａｓｅ（ＥＣ ３， ５， １， １４）是含锌金属酶，每摩 尔酶蛋白含两摩尔Ｚｎ２＋。本实验通过金属螯合剂ＥＤＴＡ对酶透析脱去酶中的锌离子， 生成不含金属离子的ａｐｏ－酶，再分别以 Ｍｎ２＋， Ｎｉ２＋离子对 ａｐｏ－酶重组，生成相 应的金属离子取代酶，研究了它们的活力与ｐＨ值的关系，热稳定性，游离的金属离子 对酶活性的影响，并通过荧光发射光谱考察了相应构象的变化。Aminoacylase (N-acylamino acid amido hydrolase, EC 3. 5. 1. 14) from pig kidney is a metalloenzyme which contains 2 moles of Zn (Ⅱ)per mole of protein. Zn2+ plays important roles in the catalysis process of enzyme. Having prepared Mn2+-substituted enzyme and Ni2+- substituted enzyme we investigated their pH-dependence and heat stability with N-chloroacetyl-DL-alanine as substrate, compared to the native enzyme. For Mn2+ or Ni2+-substituted enzymes the optimal pH is in 8. 3-8.4 range, whereas it is 7. 8 for native enzyme. Heat stability of Mn2+- substituted enzyme is almost the same as that of native enzyme, while Ni2+- substituted enzyme is less stable to heat. It was found that in the presence of excess Mn2+ ions, the activity of Mn2+-sub3tituted enzyme is 2 to 3 times higher than native enzyme. But after excess Mn2+ ions has been removed by gel filtration its activity becomes almost the same as the native enzyme. Ni2+-substituted enzyme is less active than native enzyme. The fluorescence emission spectra indicate that the emission intensity at 335nm of apo-enzyme is higher than native enzyme, while the emission intensity of Mn2+-substituted enzyme is between the apo-enzyme and native enzyme.

关 键 词：氨基酰化酶 锰 镍 猪肾 

分 类 号：Q55[生物学—生物化学]