O2-tolerant CO dehydrogenase via tunnel redesign for the removal of CO from industrial flue gas

Ni???Fe carbon monoxide dehydrogenases (CODHs) are nearly diffusion-limited biocatalysts that oxidize CO. Their O2 sensitivity, however, is a major drawback for industrial applications. Here we compare the structures of a fast CODH with a high O2 sensitivity (ChCODH-II) and a slower CODH with a lower O2 sensitivity (ChCODH-IV) (Ch, Carboxydothermus hydrogenoformans). Some variants obtained by simple point mutations of the bottleneck residue (A559) in the gas tunnel showed 61???148-fold decreases in O2 sensitivity while maintaining high turnover rates. The variant structure A559W showed obstruction of one gas tunnel, and molecular dynamics supported the locked position of the mutated side chain in the tunnel. The variant was exposed to different gas mixtures, from simple synthetic gas to sophisticated real flue from a steel mill. Its catalytic properties remained unchanged, even at high O2 levels, and the efficiency was maintained for multiple cycles of CO detoxification/regeneration

Structure of recombinant formate dehydrogenase from Methylobacterium extorquens (MeFDH1)

Abstract Formate dehydrogenase (FDH) is critical for the conversion between formate and carbon dioxide. Despite its importance, the structural complexity of FDH and difficulties in the production of the enzyme have made elucidating its unique physicochemical properties challenging. Here, we purified recombinant Methylobacterium extorquens AM1 FDH (MeFDH1) and used cryo-electron microscopy to determine its structure. We resolved a heterodimeric MeFDH1 structure at a resolution of 2.8 Å, showing a noncanonical active site and a well-embedded Fe-S redox chain relay. In particular, the tungsten bis-molybdopterin guanine dinucleotide active site showed an open configuration with a flexible C-terminal cap domain, suggesting structural and dynamic heterogeneity in the enzyme