Li Pengyun, Kuo Wen-Liang, Yousef Mohammed, Rosner Marsha Rich, Tang Wei-Jen
Ben May Institute for Cancer Research, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
Biochem Biophys Res Commun. 2006 May 19;343(4):1032-7. doi: 10.1016/j.bbrc.2006.03.083. Epub 2006 Mar 22.
Insulin degrading enzyme (IDE), a zinc metalloprotease, can specifically recognize and degrade insulin, as well as several amyloidogenic peptides such as amyloid beta (Abeta) and amylin. The disruption of IDE function in rodents leads to glucose intolerance and cerebral Abeta accumulation, hallmarks of type 2 diabetes and Alzheimer's disease, respectively. Using limited proteolysis, we found that human IDE (113kDa) can be subdivided into two roughly equal sized domains, IDE-N and IDE-C. Oligomerization plays a key role in the activity of IDE. Size-exclusion chromatography and sedimentation velocity experiments indicate that IDE-N is a monomer and IDE-C serves to oligomerize IDE-N. IDE-C alone does not have catalytic activity. It is IDE-N that contains the crucial catalytic residues, however IDE-N alone has only 2% of the catalytic activity of wild type IDE. By complexing IDE-C with IDE-N, the activity of IDE-N can be restored to approximately 30% that of wild type IDE. Fluorescence polarization assays using labeled insulin reveal that IDE-N has reduced affinity to insulin relative to wild type IDE. Together, our data reveal the modular nature of IDE. IDE-N is the catalytic domain and IDE-C facilitates substrate recognition as well as plays a key role in the oligomerization of IDE.
胰岛素降解酶（IDE）是一种锌金属蛋白酶，能够特异性识别并降解胰岛素，以及几种淀粉样生成肽，如β淀粉样蛋白（Aβ）和胰岛淀粉样多肽。啮齿动物体内IDE功能的破坏分别导致葡萄糖不耐受和脑内Aβ积累，这是2型糖尿病和阿尔茨海默病的标志。通过有限蛋白酶解，我们发现人IDE（113kDa）可大致分为两个大小相等的结构域，即IDE-N和IDE-C。寡聚化在IDE的活性中起关键作用。尺寸排阻色谱和沉降速度实验表明，IDE-N是单体，而IDE-C用于使IDE-N寡聚化。单独的IDE-C没有催化活性。关键的催化残基位于IDE-N中，然而单独的IDE-N仅具有野生型IDE 2%的催化活性。通过将IDE-C与IDE-N复合，IDE-N的活性可恢复至野生型IDE的约30%。使用标记胰岛素的荧光偏振分析表明，相对于野生型IDE，IDE-N对胰岛素的亲和力降低。总之，我们的数据揭示了IDE的模块化性质。IDE-N是催化结构域，IDE-C促进底物识别并在IDE的寡聚化中起关键作用。
