NAD+ 500 mg

What NAD+ (nicotinamide adenine dinucleotide) is

NAD+, in full nicotinamide adenine dinucleotide, is a coenzyme present in all living cells. It is neither a peptide nor a protein – the molecule consists of two nucleotides joined by a bridge of two phosphate groups. One nucleotide carries nicotinamide (the amide of nicotinic acid, i.e. vitamin B3), the other adenine. The molecular formula is C₂₁H₂₇N₇O₁₄P₂ and the molecular weight is 663.43 g/mol.

The substance was described by Arthur Harden and William Young as early as 1906 during experiments with yeast extracts; its structure was elucidated in the 1930s by Hans von Euler-Chelpin. Today NAD+ is one of the best-studied cofactors in biochemistry and appears in practically every textbook on cell metabolism.

The NAD+ and NADH redox pair

The main role of NAD+ in the cell is electron transfer. The molecule exists in two forms that convert into each other: the oxidised form NAD+ accepts electrons and becomes the reduced form NADH, which can pass them on in turn. The reaction takes place on the nicotinamide ring; the rest of the molecule serves for recognition by the enzyme.

This redox pair links the main metabolic pathways. NAD+ is consumed in glycolysis and the citric acid cycle, while the resulting NADH passes electrons to the respiratory chain in the inner mitochondrial membrane. The NAD+/NADH ratio is therefore one of the indicators used in cell studies to assess a cell's energy state.

NAD+ as a substrate: sirtuins, PARP and CD38

Besides its role as an electron carrier, NAD+ has a second function: some enzymes consume it as a substrate, cleaving the molecule in the process. They include three groups that appear most often in the literature:

• Sirtuins (SIRT1 to SIRT7) – remove acetyl groups from proteins and consume one molecule of NAD+ in every reaction. Their activity is thus directly tied to its availability in the cell.
• PARP enzymes – involved in repairing damaged DNA. With extensive damage they consume NAD+ in large amounts.
• CD38 – an ectoenzyme that cleaves NAD+ and is described in the literature as one of the factors affecting its levels in tissues.

It is this second function that explains why NAD+ appears in research on cellular ageing: the coenzyme pool is finite and several enzyme systems compete for it.

The salvage pathway and the precursors NMN and NR

Cells do not mainly make NAD+ from scratch but recycle it through the so-called salvage pathway from nicotinamide, which is produced precisely in sirtuin and PARP reactions. The key, rate-limiting step is the enzyme NAMPT. A smaller part is made de novo from the amino acid tryptophan.

Precursors that are often used in research enter the same pathway:

• NMN (nicotinamide mononucleotide) – produced by NAMPT and the immediate precursor of NAD+.
• NR (nicotinamide riboside) – converted to NMN by the enzymes NRK1 and NRK2.

The difference between NAD+ and its precursors is therefore where they enter the pathway. NAD+ is the final molecule that enzymes actually use; NMN and NR are intermediates from which the cell still has to make it.

NAD+ in ageing research

A repeatedly published observation is that NAD+ concentrations decline with age in many tissues. The explanation under discussion combines lower NAMPT activity, higher consumption by PARP enzymes as DNA damage accumulates and rising CD38 activity. These observations come mainly from cell cultures and animal models; their transferability to humans remains a matter of debate, and good-quality clinical data are still scarce.

In longevity research, NAD+ is therefore studied together with other substances involved in cell metabolism.

Reconstitution and storage

Lyophilized NAD+ is hygroscopic, meaning it readily absorbs moisture from the air. Before opening a chilled vial, let it come to room temperature so that water does not condense on the powder. Add the solvent slowly down the side of the vial and let the contents dissolve with gentle swirling, not shaking.

A 500 mg vial gives a solution with a concentration of 100 mg/ml after adding 5 ml of solvent. Our reconstitution calculator works out exact conversions for other volumes, draws in microlitres and dilutions using C1V1 = C2V2.

Store the powder dry and dark, long term at −20 °C. Keep the solution at 2–8 °C; if you will not use it within weeks, divide it into aliquots and freeze them to avoid repeated thawing. The article how to store peptides summarises the details. For reconstitution we offer bacteriostatic water.