This multiunctional enzyme catalyses both the removal of nicotinamide from NADP+, forming 2′-phospho-cyclic ADP-ribose, and the addition of nicotinate to the cyclic product, forming NAADP+, a calcium messenger that can mobilize intracellular Ca2+ stores and activate Ca2+ influx to regulate a wide range of physiological processes. In addition, the enzyme also catalyses EC 3.2.2.6, ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase.