Has in vitro nucleotide phosphodiesterase activity with nucleoside triphosphates, such as ATP (PubMed:26792860). Has in vitro activity with p-nitrophenyl-TMP. Has lower activity with nucleoside diphosphates, and no activity with nucleoside monophosphates. Has in vitro activity with CDP-choline, giving rise to CMP and phosphocholine. Has in vitro activity with CDP-ethanolamine. Does not have sphingomyelin phosphodiesterase activity (By similarity). Binds 2 Zn(2+) per subunit. Requires micromolar levels of Zn(2+) for activity. Inhibited by millimolar levels of Zn(2+). Detected in blood serum (at protein level). N-glycosylated. Belongs to the acid sphingomyelinase family.