The structural Basis of NMN synthesis catalyzed by NadV from Haemophilus ducreyi

NMN is a precursor in the biosynthesis of NAD⁺, a molecule that plays a crucial role within cells. Supplementation with NMN can elevate NAD⁺ levels in the blood, improving symptoms of diabetes, neurodegenerative diseases, and cancer, as well as providing anti-aging benefits. Escherichia coli was engineered to heterologously express nicotinamide phosphoribosyltransferase (Nampt), enabling the recombinant E. coli to synthesize NAD derivatives from nicotinamide. The 3D structure of Nadv complexed with NAM and NMN was determined to explore the molecular mechanism by which Nadv catalyzes NMN synthesis. NAM binds at two sites: one at the catalytic site and one at the allosteric binding site, while NMN binds exclusively at the catalytic site. In both structural models, a loop between β15 and β16 is missing, likely due to its high flexibility, leading to diffuse electron density. Compared with other resolved Nampt structures, an additional 12-amino-acid loop was identified after α-helix 12 near the catalytic site. This study lays the groundwork for the engineering of Nadv, facilitating its efficient application in biological synthesis of NMN.