Regulation of Myeloperoxidase Catalysis by Nitric Oxide

一氧化氮对髓过氧化物酶催化的调节

• 批准号: 6638730
• 负责人: HUSAM M ABU-SOUD
• 金额: $ 30.2万
• 依托单位: WAYNE STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-15 至 2005-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6638730
• 关键词: ascorbate; biological signal transduction; chemical kinetics; chemical structure function; computer simulation; conformation; disease /disorder model; dogs; enzyme induction /repression; enzyme model; heme; immunoregulation; intermolecular interaction; laboratory mouse; laboratory rat; model design /development; myeloperoxidase; nitric oxide; oxidation reduction reaction; peritonitis; peroxidases; peroxynitrites; respiratory function; spectrometry; stop flow technique; superoxides

Myeloperoxidase (MPO) is abundant hemoprotein present in neutrophils and monocytes which plays an essential role in immune surveillance and host defense mechanisms. It also is implicated in the pathogenesis of atherosclerosis and other inflammatory disorders. Upon phagocyte activation, MPO is secreted into both the extracellular milieu and the phagolysosome where it uses hydrogen peroxide (H2O2) produced during a respiratory burst as co-substrate. Activated intermediates, Compounds I and II, are sequentially formed which generate cytotoxic oxidants and diffusible radical species. Despite the potential significance of MPO to both human health and disease, little is known about the factors that influence MPO catalytic activity and function. In this proposal we focus on the potential role of nitric oxide (NO, nitrogen monoxide) and physiological reductants like ascorbate (Vitamin C) in the regulation of MPO activity, conformation and function. MPO and inducible nitric oxide synthase (NOS) are both stored and secreted in primary granules of activated leukocytes, and NO is known to react with the iron center of hemoproteins at near diffusion-controlled rates. However, the potential interactions between NO and the distal heme moiety of MPO are essentially unexplored. Similarly, ascorbate and other physiological reductants function in regulation the redox state of tissues. However, their role in modulating MPO catalysis through heme reduction has not been explored. The overall goal of this proposal is to identify the biochemical mechanisms through which NO and physiological reductants like ascorbate modulate MPO catalytic activity, conformation and function. We will examine the role of NO in modulating MPO activity and function and develop a comprehensive kinetic model for the interaction of nitrogen oxides with MPO. In parallel, we will examine the potential role of peroxidases in serving as a catalytic sink for NO, modulating its bioavailability and function. We will test the hypothesis that MPO-nitrosyl complexes serve as a novel mechanism for catalyzing formation of nitrosothiol adducts both in vitro and in vivo. Finally, we will explore the role of physiological reductants in reducing MPO-Fe(III) to the inactive form MPO- Fe(II), as well as characterize the role of heme reduction on MPO structure and function. Studies of MPO catalytic mechanisms and function are essential to a more fundamental understanding of the factors which govern MPO-dependent processes in human health and disease.

髓过氧化物酶（MPO）是存在于中性粒细胞和单核细胞中的丰富的血蛋白，在免疫监测和宿主防御机制中起着至关重要的作用。 它也与动脉粥样硬化和其他炎症性疾病的发病机理有关。 吞噬细胞激活后，将MPO分泌到细胞外环境和吞噬体中，它使用过氧化氢（H2O2）在呼吸爆发期间作为co肌层造期产生的氢（H2O2）。 活化的中间体，化合物I和II是依次形成的，产生细胞毒性氧化剂和可扩散的自由基物种。 尽管MPO对人类健康和疾病具有潜在的意义，但对影响MPO催化活性和功能的因素知之甚少。在此提案中，我们关注一氧化氮（NO，一氧化氮）和生理还原剂（如抗坏血酸（维生素C））在MPO活性，构象和功能的调节中的潜在作用。 MPO和诱导型一氧化氮合酶（NOS）既存储和分泌在活化白细胞的原代颗粒中，no已知与接近扩散控制速率的铁中心反应。 但是，NO和MPO的远端血红素部分之间的潜在相互作用基本上没有探索。 同样，抗坏血酸和其他生理还原剂在调节组织的氧化还原状态中起作用。 但是，尚未探索它们在通过血红素减少的调节MPO催化中的作用。 该提案的总体目标是确定生物化学机制，通过这种机制，没有抗坏血酸（如抗坏血酸）调节MPO催化活性，构象和功能。我们将研究NO在调节MPO活性和功能中的作用，并开发出一种全面的动力学模型，以使氮氧化物与MPO的相互作用。 同时，我们将研究过氧化物酶在无催化下水道中的潜在作用，从而调节其生物利用度和功能。 我们将检验以下假设：MPO-硝基酶复合物是在体外和体内催化硝基硫醇加合物形成的新机制。最后，我们将探讨生理还原剂在将MPO-FE（III）降低到非活性形式MPO-FE（II）中的作用，并表征血红素还原对MPO结构和功能的作用。 对MPO催化机制和功能的研究对于对控制人类健康和疾病中MPO依赖过程的因素的更基本了解至关重要。