What is NAD+?

NAD+ (nicotinamide adenine dinucleotide, oxidised form) is a fundamental biochemical coenzyme found in every living cell. It exists in two forms: NAD+ (oxidised) and NADH (reduced), which cycle continuously as they carry electrons in cellular metabolism.

Beyond its role as an electron carrier, NAD+ serves as an essential substrate for several classes of enzymes, including sirtuins (SIRT1-7), poly-ADP-ribose polymerases (PARPs), and CD38. These enzymes consume NAD+ as part of their catalytic activity, linking NAD+ availability to cellular signalling and maintenance pathways.

For UK research laboratories, NAD+ serves as a reference biochemical for studies examining cellular energy metabolism, mitochondrial function, enzyme kinetics, and the role of NAD+-dependent signalling in cellular ageing processes.

NAD+ operates through the following mechanisms in research models:

Redox Carrier — NAD+ accepts electrons from metabolic pathways including glycolysis, the citric acid cycle, and fatty acid oxidation, becoming NADH. NADH then donates electrons to the mitochondrial electron transport chain for ATP production.

Sirtuin Substrate — NAD+ is an essential co-substrate for sirtuin deacetylases (SIRT1-7). These enzymes remove acetyl groups from proteins in an NAD+-dependent manner, linking cellular energy status to protein acetylation and gene expression.

PARP Substrate — Poly-ADP-ribose polymerases (PARPs) consume NAD+ to synthesise ADP-ribose polymers on target proteins involved in DNA repair, genomic stability, and cellular stress responses.

CD38 Substrate — CD38 is an NAD+-consuming ectoenzyme that generates calcium-mobilising second messengers and regulates extracellular NAD+ levels.

Cellular Energy Sensing — The NAD+/NADH ratio serves as a key indicator of cellular energy status, influencing metabolic enzyme activity, gene expression, and signalling pathways that respond to energy availability.

NAD+ is employed across multiple research domains in UK laboratories:

Cellular Energy Metabolism — Biochemical assays measure NAD+/NADH ratios in cell extracts to assess metabolic state and mitochondrial function. Enzyme kinetics studies examine NAD+-dependent dehydrogenases and oxidoreductases.

Sirtuin Research — In vitro deacetylase assays use NAD+ as the essential co-substrate for studying sirtuin enzyme activity, inhibition, and regulation. Cellular models examine NAD+ availability and sirtuin-mediated gene expression.

Ageing Research — Cellular models examine NAD+ levels in the context of chronological ageing, with measurements of NAD+ decline, sirtuin activity, and mitochondrial function in aged cells.

DNA Repair Studies — PARP activity assays measure NAD+ consumption as a readout of DNA damage response. Cellular models examine the relationship between NAD+ availability and DNA repair capacity.

Comparative Biochemistry — NAD+ is used as a reference in studies comparing NAD+ precursors (nicotinamide riboside, NMN, nicotinamide) for their effects on cellular NAD+ levels and NAD+-dependent processes.

NAD+ is supplied as a lyophilised powder. Standard laboratory preparation:

• Sterile water or buffer recommended for reconstitution (avoid bacteriostatic water if benzyl alcohol interferes with downstream assays)
• Typical concentrations: 10–100 mM depending on assay requirements
• Solubility: NAD+ is highly soluble in aqueous solutions
• Light sensitivity: Protect from prolonged light exposure
• pH: Maintain solutions at pH 6.0–8.0; NAD+ is unstable at extreme pH
• Storage: Use fresh for most applications; avoid multiple freeze-thaw cycles

• Lyophilised powder: −20°C, desiccated, protected from light
• Reconstituted solution: −20°C for short-term; −80°C for extended storage
• Stability: Lyophilised powder stable for months at −20°C; reconstituted solution stable for 1–2 weeks at −20°C
• Avoid: Repeated freeze-thaw cycles; prolonged exposure to light, heat, or alkaline pH