Ca2+ signalling: a new route to NAADP.

NAADP (nicotinic acid-adenine dinucleotide phosphate) is a derivative of NADP (nicotinamide-adenine dinucleotide phosphate), which differs by the presence of a nicotinic acid instead of a nicotinamide moiety. This small structural difference makes NAADP one of the most powerful second messengers known, able to mobilize intracellular Ca2+ in a wide range of cellular models, ranging from invertebrates to mammals. Despite this, our understanding of NAADP homoeostasis, metabolism and physiological action is still limited. A new report by Vasudevan and colleagues in this issue of the Biochemical Journal provides important new data by describing a new synthetic activity in sperm cells which may turn out to represent the most physiologically relevant route to this second messenger.