Reversible Interconversion of CO₂ and Formate by a Molybdenum-Containing Formate Dehydrogenase

Abstract

CO₂ and formate are rapidly, selectively, and efficiently interconverted by tungsten-containing formate dehydrogenases that surpass current synthetic catalysts. However, their mechanism of catalysis is unknown, and no tractable system is available for study. Here, we describe the catalytic properties of the molybdenum-containing formate dehydrogenase H from the model organism Escherichia coli (<i>Ec</i>FDH-H). We use protein film voltammetry to demonstrate that <i>Ec</i>FDH-H is a highly active, reversible electrocatalyst. In each voltammogram a single point of zero net current denotes the CO₂ reduction potential that varies with pH according to the Nernst equation. By quantifying formate production we show that electrocatalytic CO₂ reduction is specific. Our results reveal the capabilities of a Mo-containing catalyst for reversible CO₂ reduction and establish <i>Ec</i>FDH-H as an attractive model system for mechanistic investigations and a template for the development of synthetic catalysts