Has in vitro nucleotide phosphodiesterase activity with nucleoside triphosphates, such as ATP. 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. Binds 2 Zn(2+) per subunit. Monomer. N-glycosylated. Belongs to the acid sphingomyelinase family.