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

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• 作者：Scot Wherland ; Kentaro Miyazaki ; Israel Pecht
• 刊名：Biochemistry
• 出版年：2016
• 出版时间：May 31, 2016
• 年：2016
• 卷：55
• 期：21
• 页码：2960-2966
• 全文大小：397K
• 年卷期：0
• ISSN：1520-4995

文摘

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.