NMNAT2 catalyzes the formation of NAD+ from nicotinamide mononucleotide (NMN) and ATP. Can also use the deamidated form nicotinic acid mononucleotide (NaMN) as a substrate but with lower efficiency. Also catalyzes the reverse reaction, i.e. the pyrophosphorolytic cleavage of NAD+. Highly expressed in brain, in particular in cerebrum, cerebellum, occipital lobe, frontal lobe, temporal lobe and putamen. Also found in the heart, skeletal muscle, pancreas and islets of Langerhans. Has been shown to correlate with Alzheimer's disease in APPswe/PS1dE9 transgenic mice and delayed wallerian degeneration in cultured superior cervical ganglia (SCGs) from morphological changes, microtubule destruction and neurofilament degradation.