Probing Electron Transfer in the Manganese‐Oxide‐Forming MnxEFG Protein Complex using Fourier Transformed AC Voltammetry: Understanding the Oxidative Priming Effect

MnxG, a multicopper oxidase, is an enzyme from the marine Bacillus species, which produces manganese oxide minerals through the aerobic oxidation of dissolved Mn2+ − a key process in global manganese geochemical cycling. When isolated in an active form as a part of the MnxEFG protein complex, the enzymatic activity of MnxG is substantially enhanced by mild oxidative priming. Herein, the mechanism for this effect is probed by using direct current (dc) and Fourier transformed alternating current (ac) voltammetric analysis of the MnxEFG complex and the catalytically inactive MnxEF subunit immobilised on a carbon electrode. Analysis of these ac voltammetric data reveals a significant enhancement in the rate of electron transfer in the Type 2 Cu sites upon oxidative priming of the enzyme, which is attributed to the improved catalytic activity of MnxG in the MnxEFG protein complex.