Chapter 6:Multiheme Peroxidases
Chapter 6:Multiheme Peroxidases
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第 6 章：多血红素过氧化物酶
DOI：
10.1039/9781782622628-00113
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Einsle
中科院分区：
文献类型：
--
作者：
Brausemann;Seidel;Einsle
活性氧的解毒是生长在微氧或有氧栖息地的任何生物的主要任务。由于其三重基态，双氧自由基在动力学上是稳定的，但它很容易与含有未配对电子的化合物反应。O2到H2O的四电子还原是有氧呼吸的驱动力，但是由于不需要的基于自由基的化学反应，单电子和双电子还原的中间体超氧化物和过氧化物构成了对细胞的实质性威胁。因此，进化已经产生了一系列酶，这些酶减少、切割或不成比例地使用这些活性氧，在该过程中几乎使用了所有的生物可利用的金属离子。对于过氧化物，血红素辅因子已被证明是非常有用的，除了在本卷其他地方讨论的具有良好特征的单功能过氧化物酶之外，本章重点介绍了一种仅在原核生物中发现的解决方案，即CcpA家族的二血红素过氧化物还原酶。1自然界已经发现了各种处理过氧化氢的方法，最常见的是过氧化氢酶，它可以使O2 2不成比例地形成O2和H2O。该过程需要还原H2O2以产生水和结合到氧化血红素基团的远端轴向位置的氧原子。然后第二个H2O2分子被氧化，从而在完全催化反应中，
The detoxification of reactive oxygen species is a major task for any organism growing in a microaerobic or aerobic habitat. With its triplet ground state, the diradical dioxygen is kinetically stable, but it reacts readily with compounds that contain unpaired electrons. The four-electron reduction of O2 to H2O is the driving force of aerobic respiration, but the one-and two-electron reduced intermediates superoxide and peroxide constitute a substantial threat for the cell due to unwanted radical-based chemistry. Consequently, evolution has brought forth a series of enzymes that reduce, cleave or disproportionate such reactive oxygen species, employing almost the complete range of bioavailable metal ions in the process. For peroxides, the heme cofactor has proven highly useful, and beside the well-characterized monofunctional peroxidases discussed elsewhere in this volume, the present chapter highlights a solution found exclusively in prokaryotes, the diheme peroxide reductases of the CcpA family. 1 Nature has found various ways for disposing of hydrogen peroxide, most commonly in catalases that elegantly disproportionate O2 2À to form O2 and H2O. This process requires the reduction of H2O2 to yield water and an oxygen atom bound to the distal axial position of the oxidized heme group. A second molecule of H2O2 then is oxidized, so that in a complete catalytic