Biotechnological production of reduced and oxidized NAD+ precursors

Dysregulation of nicotinamide adenine dinucleotide (NAD⁺) homeostasis by increased activity of NAD⁺ consumers or reduced NAD⁺ biosynthesis plays an important role in the onset of prevalent, often age-related, diseases, such as diabetes, neuropathies or nephropathies. To counteract such dysregulation, NAD⁺ replenishment strategies can be used. Among these, administration of vitamin B₃ derivatives (NAD⁺ precursors) has garnered attention in recent years. However, the high market price of these compounds and their limited availability, pose important limitations to their use in nutritional or biomedical applications. To overcome these limitations, we have designed an enzymatic method for the synthesis and purification of (1) the oxidized NAD⁺ precursors nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), (2) their reduced forms NMNH and NRH, and (3) their deaminated forms nicotinic acid mononucleotide (NaMN) and nicotinic acid riboside (NaR). Starting from NAD⁺ or NADH as substrates, we use a combination of three highly overexpressed soluble recombinant enzymes; (a) a NAD+ pyrophosphatase, (b) an NMN deamidase, and (c) a 5'-nucleotidase, to produce these six precursors. Finally, we validate the activity of the enzymatically produced molecules as NAD⁺ enhancers in cell culture.

The chemistry of the vitamin B3 metabolome

The functional cofactors derived from vitamin B3 are nicotinamide adenine dinucleotide (NAD⁺), its phosphorylated form, nicotinamide adenine dinucleotide phosphate (NADP⁺) and their reduced forms (NAD(P)H). These cofactors, together referred as the NAD(P)(H) pool, are intimately implicated in all essential bioenergetics, anabolic and catabolic pathways in all forms of life. This pool also contributes to post-translational protein modifications and second messenger generation. Since NAD⁺ seats at the cross-road between cell metabolism and cell signaling, manipulation of NAD⁺ bioavailability through vitamin B3 supplementation has become a valuable nutritional and therapeutic avenue. Yet, much remains unexplored regarding vitamin B3 metabolism. The present review highlights the chemical diversity of the vitamin B3-derived anabolites and catabolites of NAD⁺ and offers a chemical perspective on the approaches adopted to identify, modulate and measure the contribution of various precursors to the NAD(P)(H) pool.