Production and characterization of CO₂ reducing and tungsten-containing formate dehydrogenase of Cupriavidus necator H16

Formate dehydrogenases, such as MeFDH1 from Methylorubrum extorquens, efficiently convert CO₂ to formate using the tungsto-bis-metallopterin guanine dinucleotide cofactor, aiding in CO₂ emission reduction. This study characterizes a similar enzyme, tungsten-containing formate dehydrogenase from Cupriavidus necator H16, expressed in M. extorquens. CnFDW, with α and β subunits, shows high formate-forming activity (k_cat = 120 s⁻¹) using reduced ethyl viologen as an electron donor. Tungstate presence is crucial for activity, although inactive apo-CnFDW is synthesized without it. HR-ICP-MS analysis revealed a maximal tungsten content of 0.56 mol/mol enzyme, indicating 44% of enzymes lack the cofactor. CnFDW exhibited optimal formate production at 30 °C and pH 6.0, with high oxygen tolerance in the absence of formate. Docking studies suggest steric hindrance in cofactor binding reduces its activity and W content compared to MeFDH1, positioning CnFDW as a promising candidate for CO₂-to-formate conversion.