Investigations by Protein Film Electrochemistry ofAlternative Reactions of Nickel-Containing Carbon Monoxide Dehydrogenase.

Protein film electrochemistry hasbeen used to investigate reactionsof highly active nickel-containing carbon monoxide dehydrogenases(CODHs). When attached to a pyrolytic graphite electrode, these enzymesbehave as reversible electrocatalysts, displaying CO2reductionor CO oxidation at minimal overpotential. The O2sensitivityof CODH is suppressed by adding cyanide, a reversible inhibitor ofCO oxidation, or by raising the electrode potential. Reduction ofN2O, isoelectronic with CO2, is catalyzed byCODH, but the reaction is sluggish, despite a large overpotential,and results in inactivation. Production of H2and formateunder highly reducing conditions is consistent with calculations predictingthat a nickel-hydrido species might be formed, but the very low ratessuggest that such a species is not on the main catalytic pathway. [ABSTRACT FROM AUTHOR]