We report the first electrochemical study of al anthanoid-dependent methanold ehydrogenase (Eu-MDH) from the acidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV with its own physiological cytochrome c GJ electron acceptor.E u-MDH harbours ar edox active 2,7,9-tricarboxypyrroloquinoline quinone( PQQ) cofactor which is non-covalently bound but coordinates trivalent lanthanoid elements including Eu 3 + .E u-MDH and the cytochromew ere co-adsorbed with the biopolymerc hitosan and cast onto am ercaptoundecanol (MU) monolayer modified Au working electrode.C yclic voltammetry of cytochrome c GJ reveals aw ell-definedq uasi-reversible Fe III/II redox couple at + 255 mV vs. NHEa tp H7.5 and this response is pH independent. The reversible one-electronr esponseo ft he cytochrome c GJ transformsi nto as igmoidal catalytic wave in the presence of Eu-MDH and its substrates (methanol or formaldehyde). The catalyticc urrentw as pH-dependent and pH 7.3 was found to be optimal. Kinetic parameters (pHd ependence,a ctivation energy) obtained by electrochemistry show the same trends as those obtained from an artificial phenazine ethosulfate/dichlorophenol indophenol assay.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.