acid sphingomyelinase
sphingomyelin phosphodiesterase 1

alkaline sphingomyelinase
ectonucleotide pyrophosphatase/phosphodiesterase 7

neutral sphingomyelinase 3
sphingomyelin phosphodiesterase 4

SMPD2
sphingomyelin phosphodiesterase 2

SMPD3
sphingomyelin phosphodiesterase 3