Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP)

Nicotinic acid adenine dinucleotide phosphate, also known as NAADP⁺, is a nucleotide very similar to NADP, with the nicotinamide replaced with a niacin molecule. NAADP is one of the most potent Calcium signalling messenger molecules, causing release of calcium from intracellular stores.

Bifunctional ectoenzymes of the CD38 family is believed to synthesize NAADP⁺ from NADP⁺ (by exchange of nicotinamide for niacin under acidic conditions). However whether the so called base exchange reaction is responsible for NAADP generation in vivo, is questionable and remains to be proven. NAADP is believed to be hydrolysed in two selective mechanism. 1. Hydrolysis by CD38 and 2'phosphatase cleavage be a Ca2+ sensitive phosphatase. Theoretically pyrophosphatase also have the capability to hydrolyse NAADP.