Biogenic Manganese-Oxide Mineralization is Enhanced by an Oxidative Priming Mechanism for the Multi-Copper Oxidase, MnxEFG

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• 作者：Dr. Lizhi Tao ; Dr. Alexandr N. Simonov ; Dr. Christine A. Romano ; Dr. Cristina N. Butterfield ; Dr. Monika Fekete ; Prof. Bradley M. Tebo ; Prof. Alan M. Bond ; Prof. Leone Spiccia ; Assoc. Prof. Lisandra L. Martin and Prof. William H. Casey
• 刊名：Chemistry - A European Journal
• 出版年：2017
• 出版时间：January 26, 2017
• 年：2017
• 卷：23
• 期：6
• 页码：1346-1352
• 全文大小：2427K
• ISSN：1521-3765

文摘

In a natural geochemical cycle, manganese-oxide minerals (MnO_m>xm>) are principally formed through a microbial process, where a putative multicopper oxidase MnxG plays an essential role. Recent success in isolating the approximately 230 kDa, enzymatically active MnxEFG protein complex, has advanced our understanding of biogenic MnO_m>xm> mineralization. Here, the kinetics of MnO_m>xm> formation catalyzed by MnxEFG are examined using a quartz crystal microbalance (QCM), and the first electrochemical characterization of the MnxEFG complex is reported using Fourier transformed alternating current voltammetry. The voltammetric studies undertaken using near-neutral solutions (pH 7.8) establish the apparent reversible potentials for the Type 2 Cu sites in MnxEFG immobilized on a carboxy-terminated monolayer to be in the range 0.36–0.40 V versus a normal hydrogen electrode. Oxidative priming of the MnxEFG protein complex substantially enhances the enzymatic activity, as found by in situ electrochemical QCM analysis. The biogeochemical significance of this enzyme is clear, although the role of an oxidative priming of catalytic activity might be either an evolutionary advantage or an ancient relic of primordial existence.