Structure, Regulation and Mechanism of the Action of Oxidizing Enzyme

拟议的项目是在美国国家科学基金会项目下进行的研究的直接延续和扩展，利用了该调查的结果。该项目的一个方面集中在已知存在于哺乳动物线粒体中的两种形式的单胺氧化酶（MAO）对神经毒性胺MPTP （N-甲基-4-苯基-1,2,3,6-四氢吡啶）及其结构类似物的氧化，以及MPTP类似物的吡啶氧化产物对MAO A和B的可逆抑制。这些叔胺引起了生化学家、药理学家和神经生物学家的极大兴趣，因为在人类、亚人类灵长类动物和某些其他物种中，它们引起的神经系统疾病与帕金森患者的症状基本相同。它们的神经毒性作用的表达是由这些四氢吡啶被一种或两种形式的脑MAO的4电子氧化引起的。对MAO A和MAO B对这些叔胺的快速氧化的结构要求的研究揭示了这些酶的特异性的完全意想不到的方面，并且已经获得了关于它们的催化性质的重要新信息。更多种类的结构类似物仍有待用这些不同的酶形式进行测试。该计划的另一个方面进一步探讨了由MAO形成的吡啶化合物引起的神经元死亡的机制。众所周知，它们通过阻断辅酶q对黄素蛋白NADH脱氢酶的再氧化来抑制线粒体的呼吸作用。该计划下的结构-功能研究将极大地增加我们对MPP+类似物与NADH脱氢酶相互作用要求的理解。我们计划扩展我们最近的实验，这些实验已经证明了NADH脱氢酶的经典抑制剂（鱼藤酮、匹利西丁和巴比妥酸盐）在同一位点结合并与MPP+及其类似物竞争。将这些研究扩展到MPP+及其同系物的光亲和类似物，预计将确定NADH脱氢酶复合体分子的哪些亚基靠近Q还原位点。

The proposed project is a direct continuation and expansion of studies conducted under NSF project exploiting findings in that investigation. One aspect of the project centers on the oxidation of the neurotoxic amine MPTP (N- methyl-4-phenyl-1,2,3,6- tetrahydropyridine) and of its structural analogs by the two forms of monoamine oxidase )MAO), which are known to exist in mammalian mitochondria, and the reversible inhibition of MAO A and B by the pyridinium oxidation products of MPTP analogs. These tertiary amines are of profound interest to biochemists, pharmacologists, and neurobiologists because in humans, subhuman primates, and certain other species they induce neurological conditions essentially identical with those seen in Parkinson patients. Expression of their neurotoxic action is initiated by the 4-electron oxidation of these tetrahydropyridines by either or both forms of brain MAO. A study of the structural requirements of MAO A and MAO B for rapid oxidation of these tertiary amines has revealed completely unexpected facets of the specificities of these enzymes and has already yielded major new information concerning their catalytic properties. Many more classes of structural analogs remain to be tested with these different enzyme forms. Another aspect of the program explores further the mechanism of neuronal death caused by the pyridinium compounds formed by MAO. It is known that they inhibit the respiration of mitochondria by blocking the reoxidation of the flavoprotein NADH dehydrogenase by Coenzyme Q. m Structure-function studies under this proposed program should greatly increase our understanding of the requirements for the interaction of MPP+ analogs with NADH dehydrogenase. We plan to expand our recent experiments which have demonstrated that the classical inhibitors of NADH dehydrogenase (rotenone, piericidin, and barbiturates) bind at the same site and compete with MPP+ and its analogs. Extension of these studies to photoaffinity analogs of MPP+ and congeners is expected to establish which of the subunits of the complex NADH dehydrogenase molecular are close to the Q reduction site.