MAMMALIAN HEME PEROXIDASE ACTIVE SITE REACTIVITY

描述：（改编自申请人摘要）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 其特征是利用过氧化氢氧化卤化物， 拟卤离子。 白细胞和外分泌液中的过氧化物酶 产生氧化的卤化物或拟卤化物物质作为防御机制 抵抗入侵的微生物 白细胞髓过氧化物酶氧化氯 离子也可能与炎症反应有关，而这种氧化 这一过程与动脉粥样硬化有关。 外分泌液过氧化物酶 例如乳过氧化物酶利用硫氰酸根离子作为生理 衬底 直到最近才发现血红素结构， 髓过氧化物酶和乳过氧化物酶。 这些结构是前所未有的， 血红素化合物，因为常见的血红素化合物的1-和5-位甲基基团 原卟啉IX被转化为羟甲基，并且这些部分 被酯化成蛋白质的谷氨酸和天冬氨酸残基。 的 髓过氧化物酶的X-射线结构揭示了第三个共价键， 在蛋氨酸残基和蛋白质之间形成锍离子， 2-卟啉的位置乙烯基。 基本反应性 这些不寻常的血红素物种的特性值得研究， 卟啉取代基可以决定酶催化性质，并且还 就已知的哺乳动物过氧化物酶的自杀底物抑制而言。 针对这一长期目标的具体目标包括： （1）金属卟啉配合物的化学合成， 含有羟甲基或乙烯基锍离子取代基， 包括从乳过氧化物酶分离的血红素的全合成;（2） 合成化合物的物理表征，特别是 取代基对氧化还原电位的影响，以及 存在的锍离子键与氯离子氧化， 髓过氧化物酶;（3）研究合成的 修饰B自杀的乳过氧化物酶的化合物和血红素肽 基质，以及相应的改性的结构表征 血红素;和（4）不寻常的血红素结构与形成的相关性， 一种独特的，可能是抗微生物的氧化硫氰酸盐中间体。

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.