Multiple forms of the catalytic centre, Cuz, in the enzyme nitrous oxide reductase from Paracoccus pantotrophus
Multiple forms of the catalytic centre, Cuz, in the enzyme nitrous oxide reductase from Paracoccus pantotrophus
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DOI：
10.1042/bj20020055
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发表时间：
2002-06-15
影响因子：
4.1
通讯作者：
Thomson, AJ
中科院分区：
文献类型：
--
作者：
Rasmussen, T;Berks, BC;Thomson, AJ
一氧化二氮还原酶在一个独特的四核铜位置催化一氧化二氮还原为二氮，称为铜-z，它有一个中心的无机硫化物配体。与厌氧制备相比，在从泛养副球藻制备一氧化二氮还原酶的过程中，与氧气的有限孵育导致了催化中心的氧化还原性质的改变。而厌氧纯化的酶有一个催化中心，在中点电位E-m=+60 mV时，与标准氢电极(n=1)相比，该中心执行一个电子步骤，在类似的实验条件下，改变的中心没有发生氧化还原变化。这个“氧化还原固定”中心的光谱性质类似于铜-z的还原氧化还原活性形式的光谱，尽管一些跃迁的位置和强度在光学光谱中发生了变化。这些观察结果被解释为两种形式的催化中心。称为铜-z和铜-z*。这些形式之间的结构关系尚不清楚。EPR和磁性圆二色谱表明，两者都具有基本的Cu4S结构。奇怪的是。尽管催化中心没有发生可检测到的氧化还原变化，但好氧酶制剂的稳态活性略有增加。
Nitrous oxide reductase catalyses the reduction of nitrous oxide to dinitrogen at a unique tetranuclear copper site, called Cu-z, which has a central inorganic sulphide ligand. Limited incubation with oxygen during the preparation of nitrous oxide reductase from Paracoccus pantotrophus results in changed redox properties of the catalytic centre by comparison with anaerobic preparations. While the anaerobically purified enzyme has a cataltic centre which performs a single electron step at a midpoint potential of E-m = +60 mV versus the standard hydrogen electrode (n = 1) the altered centre shows no redox change under similar experimental conditions. Spectroscopic properties of this 'redox fixed' centre are similar to spectra of the reduced redox active' form of Cu-z, although the positions and intensities of a number of transitions are changed in the optical spectrum. These observations are interpreted in terms of two forms of the catalytic centre. called Cu-z and Cu-z*. The structural relationship between these forms is unclear. EPR and magnetic circular dichroism spectra suggest that the basic Cu4S structure is common to both. Curiously. steady-state activity of the aerobic enzyme preparation is slightly increased despite the fact the catalytic centre does not undergo detectable redox changes.