Biogenic manganese-oxide mineralization is enhanced by an oxidative priming mechanism for the multi-copper oxidase, MnxEFG

Lizhi Tao, Alexandr Simonov, Christine A. Romano, Cristina N. Butterfield, Monika Fekete, Bradley M. Tebo, Alan M Bond, Leone Spiccia, Lisandra L Martin, William H Casey

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7 Citations (Scopus)

Abstract

In a natural geochemical cycle, manganese-oxide minerals (MnOx) 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 MnOx mineralization. Here, the kinetics of MnOx 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.

Original languageEnglish
Pages (from-to)1346-1352
Number of pages7
JournalChemistry - A European Journal
Volume23
Issue number6
DOIs
Publication statusPublished - 26 Jan 2017

Keywords

  • direct protein electrochemistry
  • Fourier transformed AC voltammetry
  • manganese oxide mineralization
  • multi-copper oxidase activity
  • quartz crystal microbalance

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