Nicotinic acid adenine dinucleotide phosphate
![](/Images/godic/202501/29/NAADP+.svg5427.png")
![Ball-and-stick model of the NAADP molecule](/Images/godic/202501/29/Nicotinic_acid_adenine_dinucleotide_phosphate_anion_ball5427.png")
![Cell stimuli select different Ca2+ stores by synthesising different second messengers. Shown for comparison are the ER-targeting messengers, IP3 and cADPR.](/Images/godic/202501/29/NAADP_Overview5427.png")
![Speculative pathways for NAADP synthesis and degradation. ADP-ribosyl cyclase (ARC) family members (such as CD38) can synthesise NAADP via the base-exchange reaction (NicAcid, Nicotinic Acid; NiAm, nicotinamide). NAADP may be broken down to NAAD via a Ca2+-sensitive phosphatase, or to 2-phosphoadenosine diphosphoribose (ADPRP) by CD38 itself. For simplicity, enzyme topology has been ignored (see below).](/Images/godic/202501/29/NAADP_metabolism5427.png")
Nicotinic acid adenine dinucleotide phosphate, (NAADP), is a Ca-mobilizing second messenger synthesised in response to extracellular stimuli. Like its mechanistic cousins, IP3 and cyclic adenosine diphosphoribose (Cyclic ADP-ribose), NAADP binds to and opens Ca channels on intracellular organelles, thereby increasing the intracellular Ca concentration which, in turn, modulates sundry cellular processes (see Calcium signalling). Structurally, it is a dinucleotide that only differs from the house-keeping enzyme cofactor, NADP by a hydroxyl group (replacing the nicotinamide amino group) and yet this minor modification converts it into the most potent Ca-mobilizing second messenger yet described. NAADP acts across phyla from plants to man.