Biooxidation of aromatic aldehydes by aldehyde dehydrogenase from Sphingobium sp. using synthetic nicotinamide cofactor biomimetics

An aldehyde dehydrogenase SpALDH2 from Sphingobium sp. has been discovered with the unprecedented ability to utilize oxidized nicotinamide cofactor biomimetics (NCBs_ox). Among eight NCBs_ox tested, 3-carbamoyl-1-(4-carboxybenzyl) pyridin-1-ium (p-BANA⁺) enabled 96.8% conversion of syringaldehyde, comparable to NAD⁺. SpALDH2 exhibited a k_cat/K_M of 21.418 mM⁻¹ min⁻¹ with p-BANA⁺, nearly 500-fold higher than with other NCBs_ox. Molecular docking and interaction analyses suggested that hydrogen bonding and pi–pi stacking between the para-carboxyl group of p-BANA⁺ and key active-site residues contribute to its superior compatibility. These results support SpALDH2 as a promising catalyst for NCBs_ox-mediated oxidation.