Production and characterization of reduced NAADP (nicotinic acid-adenine dinucleotide phosphate)

The pyridine nucleotide NAADP (nicotinic acid-adenine dinucleotide phosphate) has been shown to act as a Ca²⁺-releasing intracellular messenger in a wide variety of systems from invertebrates to mammals and has been implicated in a number of cellular processes. NAADP is structurally very similar to its precursor, the endogenous coenzyme NADP and while much is known about the reduced form of NADP, NADPH, it is not known whether NAADP can also exist in a reduced state. Here we report that NAADP can be reduced to NAADPH by endogenous cellular enzymes and that NAADPH is functionally inert at the NAADP receptor. These data suggest that NAADPH could represent a mechanism for rapidly inactivating NAADP in cells.