Mechanistic Studies of Alkyl Hydroperoxide Reductase and Related Redox Systems

过氧化氢是人体免疫系统用来杀死感染性生物的毒素， 越来越多的证据表明，它也是真核生物信号传导中常见的第二信使。在 肿瘤坏死因子、表皮生长因子和胰岛素是被认为是激素的三个例子。 通过过氧化氢发出信号过氧化氢酶和谷胱甘肽过氧化物酶一直被认为是主要的 然而，在过去的几年里，一个独特的，高度丰富的家族， 过氧化物还原酶（Peroxiredoxins，Prxs）已经从相对默默无闻发展成为一种重要的酶， 氧化还原生物学研究的焦点。真核生物Prxs的过氧化物酶活性多年来一直被忽视， 因为那些在真核生物中高度表达的Prx很容易被过氧化物灭活。我们有 在十多年的时间里，我发展了Prx酶学方面的专业知识， 细菌（例如鼠伤寒沙门氏菌AhpC）。这些Prx是抗生素开发的目标，因为 它们在保护细菌免受人体免疫系统侵害方面所起的作用。2003年，我们的结构和 对S.鼠伤寒AhpC使我们发现了对 过氧化物，其对于在所有真核生物中高度表达的Prx的子集是保守的。我们进一步 他提出了"闸门假说"，解释了这种对失活的敏感性如何实际上有利于 过氧化氢被用作信号分子的生物体， 的Prx可以在适当的条件下关闭，以允许过氧化物的受控爆发 程度.鉴于Prxs在病原体防御和人类细胞中对抗氧化应激的重要性， 压力和细胞调节，我们建议在这里扩大我们的研究计划，既继续我们的 完善的工作，以阐明催化的基本结构和生物化学方面的 各种已知的Prxs（特定目标1，2和4），并通过开发一种新的系统生物学方法， 了解Prxs和其他过氧化物酶对真核生物中过氧化物稳态的相对贡献 具体目标3）。 氧化损伤被认为在衰老、癌症的发展和许多疾病中是重要的。 退化性疾病此外，控制增殖的细胞信号传导过程中的损伤， 分化和凋亡与许多疾病状态有关。增强对Prxs的理解 因此，它们在细胞信号传导和抗氧化保护中的作用将具有重要意义 用于预防人类疾病。此外，Prxs在保护人类病原体免受 免疫系统的杀伤暗示Prx是开发新治疗剂的靶点， 防治传染病。

Hydrogen peroxide is a toxin used by the human immune system to kill infectious organisms, and increasing evidence is accumulating that it is also a common second messenger in eukaryotic signaling. In humans, tumor necrosis factor, epidermal growth factor and insulin are three examples of hormones thought to signal via hydrogen peroxide. Catalase and glutathione peroxidase have long been viewed as the major nzymes degrading peroxide in cells, however, over the past few years, a distinct, highly abundant family of peroxide-reducing enzymes, peroxiredoxins (Prxs), have moved from relative obscurity to become a major Focus of redox biology research. The peroxidase activity of eukaryotic Prxs was overlooked for many years, because those Prxs that are highly expressed in eukaryotes are easily inactivated by peroxide. We have developed expertise in Prx enzymology over more than a decade of characterizing of Prxs from pathogenic bacteria (e.g. Salmonella typhimurium AhpC). These Prxs are targets for antibiotic development because of the role they play in protecting the bacteria from the human immune system. In 2003, our structural and functional studies on S. typhimurium AhpC led us to discover the structural basis for the sensitivity toward peroxides that is conserved for a subset of Prxs that are highly expressed across all eukarya. We further proposed the "floodgate hypothesis" for how this sensitivity to inactivation would actually be beneficial in organisms where hydrogen peroxide is being used as a signaling molecule, so that the antioxidant properties of the Prxs could be switched off under appropriate conditions to allow for a controlled burst in peroxide levels. Given the importance of Prxs both in pathogen defense and in human cells for combating oxidative stress and for cellular regulation, we propose here to expand our research program by both continuing our well-established work to elucidate the fundamental structural and biochemical aspects of catalysis by the variety of known Prxs (Specific Aims 1, 2, and 4) and by developing a novel systems biology approach to understand the relative contributions of Prxs and other peroxidases to peroxide homeostasis in eukaryotic cells (Specific Aim 3). Oxidative damage is thought to be important in aging, in the development of cancer and in many degenerative diseases. Moreover, impairments in cell signaling processes controlling proliferation, differentiation and apoptosis are associated with many disease states. An enhanced understanding of Prxs and the roles they play in both cell signaling and antioxidant protection will thus have important implications for the prevention of human diseases. In addition, the role of Prxs in protecting human pathogens against killing by the immune system implicates Prxs as targets for the development of new therapeutic agents to combat infectious diseases.