The first step in the synthesis of nicotinamide adenine dinucleotide (NAD+) is the formation of nicotinate ribonucleotide from nicotinate and PRPP. Nicotinate (also called niacin) is derived from tryptophan. Humans can synthesis the required amount of nicotinate if the supply of tryptophan in the diet is adequate. However, an exogenous supply of nicotinate is required if dietary intake of tryptophan is low. A dietary deficiency of tryptophan and nicotinate can lead to pellagra, a disease characterized by dermatitis, diarrhea and dementia. An AMP moiety is then transferred from ATP to nicotinate ribonucleotide to form desamido-NAD+. The final step is the transfer of the amide group of glutamine to the nicotinate carboxyl group to form NAD+.
|NAD Home||Introduction||Example I: Alcohol Dehydrogenase||Example II: Glyceraldehyde-3-Phosphate Dehydrogenase||Example III: Lactate Dehydrogenase||References|