Intramolecular Electron Transfer in the Bacterial Two-Domain Multicopper Oxidase mgLAC,Biochemistry

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Intramolecular Electron Transfer in the Bacterial Two-Domain Multicopper Oxidase mgLAC
Biochemistry ( IF 2.9 ) Pub Date : 2016-05-17 00:00:00 , DOI: 10.1021/acs.biochem.6b00158
Scot Wherland ₁ , Kentaro Miyazaki ₂ , Israel Pecht ₃

Affiliation

The kinetics of the intramolecular electron transfer process in mgLAC, a bacterial two-domain multicopper oxidase (MCO), were investigated by pulse radiolysis. The reaction is initiated by CO₂^– radicals produced in anaerobic, aqueous solutions of the enzyme by microsecond pulses of radiation. A sequence of pulses of CO₂^– radicals enables examination of the reductive half-cycle of the MCO catalysis. This is done by titrations of the Type 1 (T1) Cu(II) site and monitoring of the time course and amplitude of its reoxidation by internal electron transfer (ET) to the Type 3 site. Comparison of the internal ET kinetics observed for mgLAC with those of other MCOs studied by pulse radiolysis shows that they exhibit distinct reactivities. One main cause for the different reactivities is the broad range of T1 copper redox potentials, from the moderate potential of bacterial enzymes to the high potential of fungal laccases, and this possibly also reflects evolutionary quaternary structural adaptation of the MCO family to the wide range of reducing substrates that they oxidize while maintaining efficient reduction of the common substrate, molecular oxygen.

中文翻译：

细菌两域多铜氧化酶mgLAC中的分子内电子转移

通过脉冲辐射分析研究了mgLAC（一种细菌两域多铜氧化酶（MCO））中分子内电子转移过程的动力学。该反应由CO发起₂^-在厌氧产生的自由基，通过辐射的微秒脉冲的酶的水溶液。一连串的CO ₂脉冲^–自由基能够检查MCO催化的还原性半循环。这是通过滴定1型（T1）Cu（II）位点并通过内部电子转移（ET）到3型位点监测其再氧化的时间过程和幅度来完成的。用mgLAC观察到的内部ET动力学与通过脉冲辐解研究的其他MCO的内部ET动力学比较表明，它们表现出不同的反应性。导致不同反应性的一个主要原因是T1铜氧化还原电位的范围很广，从中等程度的细菌酶电位到真菌漆酶的高电位，这也可能反映了MCO家族对大范围的M4家族的进化季结构适应性。还原它们氧化的底物，同时保持有效还原常见底物分子氧的效率。

更新日期：2016-05-17

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