Electrocatalysis of a Europium‐Dependent Bacterial Methanol Dehydrogenase with Its Physiological Electron‐Acceptor Cytochrome cGJ

We report the first electrochemical study of a lanthanoid‐dependent methanol dehydrogenase (Eu‐MDH) from the acidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV with its own physiological cytochrome cGJ electron acceptor. Eu‐MDH harbours a redox active 2,7,9‐tricarboxypyrroloquinoline quinone (PQQ) cofactor which is non‐covalently bound but coordinates trivalent lanthanoid elements including Eu3+. Eu‐MDH and the cytochrome were co‐adsorbed with the biopolymer chitosan and cast onto a mercaptoundecanol (MU) monolayer modified Au working electrode. Cyclic voltammetry of cytochrome cGJ reveals a well‐defined quasi‐reversible FeIII/II redox couple at +255 mV vs. NHE at pH 7.5 and this response is pH independent. The reversible one‐electron response of the cytochrome cGJ transforms into a sigmoidal catalytic wave in the presence of Eu‐MDH and its substrates (methanol or formaldehyde). The catalytic current was pH‐dependent and pH 7.3 was found to be optimal. Kinetic parameters (pH dependence, activation energy) obtained by electrochemistry show the same trends as those obtained from an artificial phenazine ethosulfate/dichlorophenol indophenol assay. Current asset: The electrochemical study of a lanthanoid‐dependent methanol dehydrogenase (Eu‐MDH) from the acidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV with its own physiological cytochrome cGJ electron acceptor is reported. The reversible one‐electron response of cytochrome cGJ transforms into a sigmoidal catalytic wave in the presence of Eu‐MDH and its substrates methanol (see figure) or formaldehyde.