Sphingomyelin phosphodiesterase 4 (neutral sphingomyelinase 3, nSMase3, nSMase-3, SMPD4, KIAA1418)

Function

• catalyzes hydrolysis of membrane sphingomyelin to form phosphorylcholine & ceramide
• activated by phosphatidylserine & tumor necrosis factor (TNF)
• inhibited by scyphostatin

Sphingomyelin + H2O <--> N-acylsphingosine + choline phosphate

Cofactor: Mg+2

Kinetic parameters

• Optimum pH is 7.0

Compartment

• endoplasmic reticulum membrane
• Golgi apparatus membrane

Alternative splicing

named isoforms=5

Expression

• widely expressed
• highest levels in heart & skeletal muscle

More general terms

• sphingomyelinase, sphinogomyelin phosphodiesterase
• membrane protein

Database

• UniProt: http://www.uniprot.org/uniprot/Q9NXE4.html