NAD and Cellular Energy: What a Coenzyme Is and Is Not
NAD is stocked alongside research peptides but it is not a peptide, and treating it as one leads to avoidable errors in handling and in experimental design.
What it is
Nicotinamide adenine dinucleotide is a dinucleotide: two nucleotides joined through their phosphate groups. It is a small molecule, not an amino acid polymer, and it has no sequence, no termini and no secondary structure.
Two distinct roles
The first is as a redox carrier. NAD+ accepts a hydride to become NADH, and the couple shuttles reducing equivalents through glycolysis, the citric acid cycle and oxidative phosphorylation. In this role it is recycled, not consumed — the pool cycles.
The second role is as a consumed substrate. Sirtuins, PARPs and CD38 cleave NAD+ and use it up, releasing nicotinamide. This is why NAD+ availability is discussed as a limiting factor in some model systems in a way that a purely catalytic cofactor would not be: one set of enzymes recycles it and another set destroys it.
The indexed literature is at PubMed.
Handling differences from peptides
NAD+ is considerably more water-soluble than most peptides and dissolves readily without the pH manipulation that a hydrophobic sequence needs. It is, however, chemically unstable in alkaline solution, where the nicotinamide-ribose bond hydrolyses. Preparing stocks in a basic buffer — an approach that suits acidic peptides — is the wrong instinct here.
It is also light-sensitive in solution, and NADH more so than NAD+. Amber vessels and prompt use are sensible precautions.
Assay note
Because NAD+ and NADH differ in absorbance at 340 nm, the redox state of a preparation can be checked spectrophotometrically without a dedicated assay. That is a useful quick sanity check on material that has been stored in solution.
Related compounds
NAD is grouped with mitochondrial and cellular compounds alongside MOTS-c and SS-31, which are genuine peptides with unrelated mechanisms — see SS-31 and cardiolipin. Products: NAD 500mg and NAD 1000mg.
ExoLabz supplies compounds for laboratory research use only. Nothing on this page is medical advice or a suggestion of human or veterinary use. Certificates of analysis are published on this site.
