Electron transport system on complex flavoprotein

黄嘌呤氧化酶和黄嘌呤脱氢酶是复杂的金属黄素蛋白，似乎代表同一基因产物的不同形式。哺乳动物的酶最初是以脱氢酶的形式存在的，但在提取或纯化过程中会转化为氧化酶。该酶由两个相同的亚基组成，催化尿酸代谢的最后两步，此外，还参与活性氧基的产生。亚基的相对分子质量约为15万，每个亚基含有一个钼杂多酚、两个铁硫中心和一个FAD。在催化反应中，电子在辅助因子之间传递。因此，这种酶本身就含有电子传递系统。因此，它可能是了解线粒体和微粒体中电子传递系统的一个很好的模型。我们的目标之一是更详细地了解酶反应的催化机理和控制机理。在一定的时间内，我们制作了…1)鸡肝黄嘌呤脱氢酶的结构分析[FASE B J.9995-1003,1995；[J Biol.Chem.270,2818-2826,1995]，2)新型抑制剂-8-(3-甲氧基-4-苯基亚磺基苯基)吡唑并[1，5-a]-1，3，5-三嗪-4-酸酯一水合物对乳酶催化作用的机理分析[J.Biol.Chem.，270,7816-7821,1995]，3)硫代丙酮酸硫转移酶结构与功能关系的分析[J Biol.Chem，270,16230-16235,1995；J.Biol.Chem.，271,27395-27401,1996]，4)利用重组DNA技术和酶分析在杆状病毒中表达野生型和突变型黄嘌呤氧化酶，以及5)使用重组DNA技术表达野生型和突变型超氧化物歧化酶并分析结构-功能关系：[Frontiers of Reactive Off Species in Biology and Medicine，Elsevier Science Publisher，B.V.，Amusteram，135-136,1994]。较少

Xanthine oxidase and xanthine dehydrogenase are complex metalloflavoproteins that appear to represent alternate forms of the same gene product. The mammalian enzyme exists originally as a dehydrogenase, but it converts to an oxidase during extraction or purification prosedues. The enzyme is formed with two identical subunits, catalyzes the final two step in uric acid metabolism and, in addition, participates also the production of active oxigen species. The molecular weight of subunit is about 150,000, and each contains one molybdopterin, two iron sulfur centers and one FAD.During the catalytic reaction the electrons are transfed between the co-factors. Thus the enzyme contains the electron transport system in itself. Therefor it might be a good model for understanding of electron transfort system in mitochondria and in microsome. One of our gole is to understand the catalytic mechanism and contral mechanism on the enzyme reaction in further detail.Within a given period of time, we mak … More ed up the following studies : 1) analysis of the structure of chickin liver xanthine dehydrogenase which has never been known to convert to an oxidase : [FASEB J.9,995-1003,1995 ; J.Biol.Chem.270,2818-2826,1995], 2) analysis of the mechanism of inhibition by a new inhibitor, sodium-8-(3-methyoxy-4-phenylsulfinylphenyl) pyrazolo [1,5-a]-1,3,5-triazine-4-olate monohydrate, to the catalytic action of milk enzyme : [J.Biol.Chem., 270,7816-7821,1995], 3) analysis of the structure-function relationship of mercaptopyruvate sulfurtransferase which thought to play a role on incorpolation of sulfur into the iron-sulfur protein : [J.Biol.Chem., 270,16230-16235,1995 ; J.Biol.Chem., 271,27395-27401,1996], 4) the expression of wild-type and mutant-type xanthine oxidases in bacurovirus using recombinant DNA technology and the enzymetic analysis and 5) the expression of wild-type and mutant-type superoxide dismutases using recombinant DNA technology and analysis of the structure-function relationship : [Frontiers of reactive oxygen species in biology and medicine, Elsevier Scientific Publishers, B.V., Amusterdam, 135-136,1994]. Less