Nicotinamide adenine dinucleotide as a photocatalyst

Abstract

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 O2 reduction, H2O 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−1 and 1692.3, respectively, for light-driven biocatalytic trans-hydrogenation.

Bioinspired NADH Regeneration Based on Conjugated Photocatalytic Systems

“…Interestingly, the oxidized form, NAD + , was recently reported to serve as a molecular photocatalyst itself for photocatalytic redox reactions benefiting from the π–π* electronic transition of nicotinamide and adenine in the molecular structure. [ 95 ] The direct photoactivation of oxidoreductases can be achieved using NAD + as photocatalyst, which exhibits systematic simplicity and high efficiency. For completing NADH regeneration and photoenzymatic reaction in an economic and sustainable manner, there are still several challenges to overcome in this field.…”

Nature is the Cure: Engineering Natural Redox Cofactors for Biomimetic and Bioinspired Catalysis

“…Interestingly, this system efficiently performs the asymmetric reduction of C=C bonds coupled with biocatalytic water oxidation, and the results compare well with biotransformations performed in whole cells (99 % ee, 80 % yield for N‐methyl maleimide, Scheme , b). Interestingly, it was recently reported that, in addition to its wide‐ranging biological roles, NAD + can act as a photocatalyst and perform new light‐induced redox reactions among which O 2 reduction, H 2 O oxidation and nanoparticles generation through metal reduction …”

“…Interestingly, it was recently reported that, in addition to its wide-ranging biological roles, NAD + can act as a photocatalyst and perform new light-induced redox reactions among which O 2 reduction, H 2 O oxidation and nanoparticles generation through metal reduction. [34] A strategy for the regeneration of synthetic nicotinamide cofactors was devised using two enzymes and a biomimetic nicotinamide analogue, which shuttles between both enzymatic cycles. [35] The first enzyme is an engineered double mutant form of SsGDH, a glucose dehydrogenase from Sulfolobus solfataricus, while the second enzyme is TsER, an enoate reductase from Thermus scotoductus.…”

Water-Soluble Anthraquinone Photocatalysts Enable Methanol-Driven Enzymatic Halogenation and Hydroxylation Reactions

“… 8 − 10 Furthermore, combining photocatalysis with biocatalysis offers new possibilities for organic synthesis ranging from new regeneration approaches for cofactor-dependent enzymes, 11 − 25 photoenzymatic cascades, 26 and “new to nature” reactions catalyzed by photoexcited enzymes. 27 − 32 Yet, the combination of photocatalysis with biocatalysis is not always unproblematic due to issues of photobleaching 33 and formation of reactive oxygen species. 34 − 36 …”