Nicotinamide mononucleotide adenylyltransferase (NMNAT) (EC2.7.7.1) is a central enzyme in NAD+ biosynthesis, transferring the adenylyl moiety of ATP to nicotinamide mononucleotide (NMN) or nicotinic acid mononucleotide (NaMN) resulting in the formation of NAD+ or NaAD+ and the release of pyrophosphate. As this reaction is reversible, the enzyme may in principle be used to form ATP and NMN from NAD+ and pyrophosphate.
NMNAT2 is predominantly expressed in human pancreas, insulinoma as well as in the brain, especially in the cerebrum, cerebellum, occipital lobe, frontal lobe, temporal lobe and putamen. Immunofluorescence microscopy localized endogenous NMNAT2 to the Golgi apparatus in human cell line. Endogenous NMNAT2 seem to be a labile axon survival factor, because specific depletion of NMNAT2 is sufficient to induce Wallerian-like degeneration of uninjured axons which endogenous NMNAT1 and NMNAT3 cannot prevent. Thus endogenous NMNAT2 represents an exciting new therapeutic target for axonal disorders.