The GO annotation for this family indicates that it is a single-pass membrane protein, and it appears to be found in mitochondrial membranes. Sphingolipids play important roles in regulating cellular responses, and although mitochondria contain sphingolipids, direct regulation of their levels in mitochondria or mitochondria-associated membranes is mostly unclear. Sphingomyelin phosphodiesterases catalyse the hydrolysis of sphingomyelin to ceramide and phosphocholine, and these metabolites are involved in signalling pathways.

1: A deletion in the gene encoding sphingomyelin phosphodiesterase 3 (Smpd3) results in osteogenesis and dentinogenesis imperfecta in the mouse. Aubin I, Adams CP, Opsahl S, Septier D, Bishop CE, Auge N, Salvayre R, Negre-Salvayre A, Goldberg M, Guenet JL, Poirier C; Nat Genet. 2005;37:803-805. PMID:16025116

2: Identification and characterization of murine mitochondria-associated neutral sphingomyelinase (MA-nSMase), the mammalian sphingomyelin phosphodiesterase 5. Wu BX, Rajagopalan V, Roddy PL, Clarke CJ, Hannun YA; J Biol Chem. 2010;285:17993-18002. PMID:20378533