Synthesizes the second messengers cyclic ADP-ribose and nicotinate-adenine dinucleotide phosphate, the former a second messenger for glucose-induced insulin secretion. Also has cADPr hydrolase activity. Regulates osteoclastic bone resorption, probably via production of cyclic ADP-ribose and triggering of a cytosolic calcium ion signal through ryanodine receptor activation. H2O + NAD(+) = ADP-D-ribose + H(+) + nicotinamide NADP(+) + nicotinate = nicotinamide + nicotinate-adenine dinucleotide phosphate Spleen, liver, heart, thymus, thyroid gland, ileum, colon, cerebellum, salivary gland, adrenal gland, jejunum, islets of Langerhans and osteoclasts. Belongs to the ADP-ribosyl cyclase family.