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Proton-coupled electron transfer mechanisms of the copper centres of nitrous oxide reductase from Marinobacter hydrocarbonoclasticus - An electrochemical study.
Bioelectrochemistry ( IF 5 ) Pub Date : 2020-02-16 , DOI: 10.1016/j.bioelechem.2020.107483
Cíntia Carreira 1 , Margarida M C Dos Santos 2 , Sofia R Pauleta 3 , Isabel Moura 4
Affiliation  

Reduction of N2O to N2 is catalysed by nitrous oxide reductase in the last step of the denitrification pathway. This multicopper enzyme has an electron transferring centre, CuA, and a tetranuclear copper-sulfide catalytic centre, "CuZ", which exists as CuZ*(4Cu1S) or CuZ(4Cu2S). The redox behaviour of these metal centres in Marinobacter hydrocarbonoclasticus nitrous oxide reductase was investigated by potentiometry and for the first time by direct electrochemistry. The reduction potential of CuA and CuZ(4Cu2S) was estimated by potentiometry to be +275 ± 5 mV and +65 ± 5 mV vs SHE, respectively, at pH 7.6. A proton-coupled electron transfer mechanism governs CuZ(4Cu2S) reduction potential, due to the protonation/deprotonation of Lys397 with a pKox of 6.0 ± 0.1 and a pKred of 9.2 ± 0.1. The reduction potential of CuA, in enzyme samples with CuZ*(4Cu1S), is controlled by protonation of the coordinating histidine residues in a two-proton coupled electron transfer process. In the cyclic voltammograms, two redox pairs were identified corresponding to CuA and CuZ(4Cu2S), with no additional signals being detected that could be attributed to CuZ*(4Cu1S). However, an enhanced cathodic signal for the activated enzyme was observed under turnover conditions, which is explained by the binding of nitrous oxide to CuZ0(4Cu1S), an intermediate species in the catalytic cycle.

中文翻译:

破损海事杆菌的一氧化二氮还原酶铜中心的质子耦合电子转移机理-电化学研究。

N2O还原为N2是在反硝化途径的最后一步中由一氧化二氮还原酶催化的。这种多铜酶具有一个电子转移中心CuA和一个四核硫化铜催化中心“ CuZ”,以CuZ *(4Cu1S)或CuZ(4Cu2S)的形式存在。通过电位法研究了这些金属中心在Marinobacter烃裂质一氧化二氮还原酶中的氧化还原行为,这是首次通过直接电化学研究。在pH 7.6下,通过电位计估计的CuA和CuZ(4Cu2S)的还原电位相对于SHE分别为+275±5 mV和+65±5 mV。由于Lys397的质子化/去质子化的pKox为6.0±0.1,pKred为9.2±0.1,质子耦合电子传递机制决定了CuZ(4Cu2S)的还原电位。CuA的还原潜力 带有CuZ *(4Cu1S)的酶样品中的Cn在两个质子耦合电子转移过程中受配位组氨酸残基的质子化控制。在循环伏安图中,确定了两个对应于CuA和CuZ(4Cu2S)的氧化还原对,未检测到可归因于CuZ *(4Cu1S)的其他信号。但是,在周转条件下观察到了活化酶的增强的阴极信号,这可以通过一氧化二氮与催化循环中的中间物种CuZ0(4Cu1S)的结合来解释。没有检测到可归因于CuZ *(4Cu1S)的其他信号。但是,在周转条件下观察到了活化酶的增强的阴极信号,这可以通过一氧化二氮与催化循环中的中间物种CuZ0(4Cu1S)的结合来解释。没有检测到可归因于CuZ *(4Cu1S)的其他信号。但是,在周转条件下观察到了活化酶的增强的阴极信号,这可以通过一氧化二氮与催化循环中的中间物种CuZ0(4Cu1S)的结合来解释。
更新日期:2020-02-20
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