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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Synthetic iron-oxo 'diamond core' mimics structure of key intermediate in methane monooxygenase catalytic cycle
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Synthetic iron-oxo 'diamond core' mimics structure of key intermediate in methane monooxygenase catalytic cycle

机译：合成的铁-氧“钻石核”模拟甲烷单加氧酶催化循环中关键中间体的结构

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Molecular oxygen (O_2) is the principal oxidant used by aerobic organisms to carry out a wide range of metabolic reactions and transformations. The enzymes involved in these processes use a rich variety of different active sites to activate O_2, such as heme cofactors, mono- and binuclear nonheme iron centers, mono- and binuclear copper complexes, and heteronuclear heme iron/copper clusters (1). Typically, oxygen is activated in a tightly controlled manner to ensure that the formation of the key reactive species in the corresponding catalytic cycle occurs only when the target substrate is present, thereby suppressing potentially harmful side reactions in the enzyme active site (2). A particularly well studied example of an enzyme that follows this general strategy is provided by cytochrome P450 (3). As outlined in Fig. 1 Upper, binding of substrate to the heme-containing active site of cytochrome P450 causes dissociation of the Fe~(Ⅲ)-bound water ligand, thereby triggering the reduction of the iron center to the reactive Fe~(Ⅱ) state. The Fe" species binds and activates O_2 to generate an iron(Ⅳ)-oxo porphyrin radical intermediate. This highly potent oxidant then proceeds to incorporate one of the O atoms derived from molecular oxygen into a specific C—H bond of the substrate, in a process that yields the oxidized product and restores the resting Fe~(Ⅲ) state of the enzyme. High-valent intermediates have also been identified in the catalytic cycles of an increasing number of nonheme diiron enzymes (1, 4), such as methane monooxygenase (MMO) (2, 5). Found in methanotropic bacteria, MMO catalyzes the chemically challenging conversion of methane to methanol (Fig. 1 Lower), thereby reducing the amount of this greenhouse gas that is being released into the atmosphere by nearly 1 billion tons per year (6).
机译：分子氧（O_2）是有氧生物用于进行广泛的代谢反应和转化的主要氧化剂。这些过程中涉及的酶使用各种不同的活性位点来激活O_2，例如血红素辅因子，单核和双核非血红素铁中心，单核和双核铜络合物以及异核血红素铁/铜簇（1）。通常，以严格控制的方式激活氧气，以确保仅在存在目标底物时才在相应的催化循环中形成关键的反应性物种，从而抑制酶活性位点中可能有害的副反应（2）。细胞色素P450（3）提供了一个遵循这种普遍策略的经过特别研究的酶实例。如图1上部所示，底物与细胞色素P450含血红素的活性位点的结合导致结合Fe〜（Ⅲ）的水配体解离，从而触发了铁中心向反应性Fe〜（Ⅱ）的还原。 ）状态。 Fe”物种结合并激活O_2以生成铁（Ⅳ）-氧卟啉自由基中间体。然后，这种强氧化剂将来自分子氧的O原子之一掺入底物的特定CH键中。生成氧化产物并恢复该酶的静态Fe〜（Ⅲ）状态的过程，还已经在越来越多的非血红素二铁酶（1、4）的催化循环中发现了高价中间体，例如甲烷单加氧酶（MMO）（2，5）。在甲烷多变细菌中发现，MMO催化从化学上具有挑战性的甲烷到甲醇的转化（图1下），从而将释放到大气中的这种温室气体减少了近1％。每年十亿吨（6）。

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