Redox Characterization of the Complex Molybdenum Enzyme Formate Dehydrogenase from .

The oxygen-tolerant and molybdenum-dependent formate dehydrogenase FdsDABG from is capable of catalyzing both formate oxidation to CO and the reverse reaction (CO reduction to formate) at neutral pH, which are both reactions of great importance to energy production and carbon capture. FdsDABG is replete with redox cofactors comprising seven Fe/S clusters, flavin mononucleotide, and a molybdenum ion coordinated by two pyranopterin dithiolene ligands. The redox potentials of these centers are described herein and assigned to specific cofactors using combinations of potential-dependent continuous wave and pulse EPR spectroscopy and UV/visible spectroelectrochemistry on both the FdsDABG holoenzyme and the FdsBG subcomplex. These data represent the first redox characterization of a complex metal dependent formate dehydrogenase and provide an understanding of the highly efficient catalytic formate oxidation and CO reduction activity that are associated with the enzyme.