MAMMALIAN HEME PEROXIDASE ACTIVE SITE REACTIVITY

哺乳动物血红素过氧化物酶活性位点反应性

• 批准号: 6180818
• 负责人: HAROLD M. GOFF
• 金额: $ 17.15万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6180818
• 关键词: active sites; chemical synthesis; chloride ion; enzyme activity; heme; lactoperoxidase; mass spectrometry; metalloporphyrins; myeloperoxidase; nuclear magnetic resonance spectroscopy; oxidation; peroxidases; sulfur compounds; thiocyanates

DESCRIPTION: (adapted from applicant's abstract) Mammalian heme peroxidase enzymes are distributed in various tissues, but the common reactivity feature is utilization of hydrogen peroxide for oxidation of halide or pseudo-halide ions. Peroxidases in leucocytes and in the exocrine fluids generate oxidized halide or pseudo-halide species as a defense mechanism against invading microbes. Leucocyte myeloperoxidase oxidation of chloride ion may also be associated with an inflammatory response, and this oxidative process has been implicated in atherogenesis. Exocrine fluid peroxidases such as lactoperoxidas utilize thiocyanate ion as the physiological substrate. Only very recently hav the heme structures been identified for myeloperoxidase and lactoperoxidase. The structures are unprecedented for heme compounds, in that the 1- and 5-position methyl groups of the common protoporphyrin IX are converted to hydroxymethyl groups, and these moieties are esterified to glutamate and aspartate residues of the protein. The X-ray structure of myeloperoxidase reveals a third covalent linkage to the protein with sulfonium ion formation between a methionine residue and the 2-position vinyl group of the porphyrin. The fundamental reactivity properties of these unusual heme species merit investigation in terms of how the porphyrin substituents may dictate enzyme catalytic properties, and also in terms of known suicide substrate inhibition of the mammalian peroxidases. The specific objectives directed toward this long-term goal include the following: (1) chemical synthesis of metalloporphyrin complexes that contain either the hydroxymethyl or the vinyl sulfonium ion substituents, to include total synthesis of the heme isolated from lactoperoxidase; (2) physical characterization of the synthetic compounds with particular regard to substituents effects on redox potentials, and a correlation of the presence of the sulfonium ion linkage with chloride ion oxidation by myeloperoxidase; (3) investigation of the susceptibility of the synthetic compounds and the heme peptides of lactoperoxidase to modification b suicide substrates, with corresponding structural characterization of modified hemes; and (4) correlation of the unusual heme structures with formation of a unique, presumably antimicrobial oxidized thiocyanate intermediate.

描述：（改编自申请人的摘要）哺乳动物血红素过氧化物酶 酶分布在各种组织中，但共同的反应性 特征是利用过氧化氢来氧化卤化物或 伪卤离子。 白细胞中的过氧化物酶和外分泌液中的过氧化物酶 产生氧化的卤化物或伪卤化物作为防御机制 反对入侵微生物。 白细胞骨髓过氧化物酶的氯化物氧化 离子也可能与炎症反应有关，这种氧化性 过程与动脉粥样硬化有关。 外分泌液过氧化物酶 例如乳酸氧化剂利用硫氰酸酯离子作为生理 基材。 只有最近才确定血红素结构 骨髓过氧化物酶和乳糖氧化酶。 这些结构是前所未有的 血红素化合物，是共同的1和5位甲基 原源性IX转化为羟基甲基，这些部分 酯化为蛋白质的谷氨酸和天冬氨酸残基。 这 骨髓过氧化物酶的X射线结构揭示了与 蛋白质在蛋氨酸残基和 卟啉的2位乙烯基。 基本反应性 这些不寻常的血红素物种的特性值得研究 卟啉取代基可能决定酶催化特性，还可以决定 根据已知的自杀底物抑制哺乳动物过氧化物酶的抑制。 针对这个长期目标的具体目标包括 以下：（1）金属卟啉复合物的化学合成 包含羟甲基或乙烯基磺硫离子取代基的 包括从乳糖氧化酶分离的血红素的总合成； （2） 具有特定方面的合成化合物的物理表征 取代基对氧化还原电势的影响，以及 通过通过氯离子氧化的磺基离子连接的存在 髓过氧化物酶； （3）调查合成的敏感性 乳酸氧化酶的化合物和血红素肽以修饰B自杀 底物，具有相应的修饰的结构表征 hemes; （4）不寻常的血红素结构与形成 一种独特的，大概是抗菌氧化的硫代盐中间体。