Nicotinamide adenine dinucleotide as a photocatalyst.

Nicotinamide adenine dinucleotide (NAD) is a key redox compound in all living cells responsible for energy transduction, genomic integrity, life-span extension, and neuromodulation. Here, we report a new function of NAD as a molecular photocatalyst in addition to the biological roles. Our spectroscopic and electrochemical analyses reveal light absorption and electronic properties of two π-conjugated systems of NAD. Furthermore, NAD exhibits a robust photostability under UV-Vis-NIR irradiation. We demonstrate photocatalytic redox reactions driven by NAD, such as O reduction, HO oxidation, and the formation of metallic nanoparticles. Beyond the traditional role of NAD as a cofactor in redox biocatalysis, NAD executes direct photoactivation of oxidoreductases through the reduction of enzyme prosthetic groups. Consequently, the synergetic integration of biocatalysis and photocatalysis using NAD enables solar-to-chemical conversion with the highest-ever-recorded turnover frequency and total turnover number of 1263.4 hour and 1692.3, respectively, for light-driven biocatalytic trans-hydrogenation.