Acid Sphingomyelinase (SMPD1) Antibody – Rabbit Polyclonal

The protein encoded by this gene is a lysosomal acid sphingomyelinase that converts sphingomyelin to ceramide. The encoded protein also has phospholipase C activity. Defects in this gene are a cause of Niemann-Pick disease type A (NPA) and Niemann-Pick disease type B (NPB). Multiple transcript variants encoding different isoforms have been identified. [provided by RefSeq, Jul 2010]

Function: Converts sphingomyelin to ceramide. Also has phospholipase C activities toward 1,2-diacylglycerolphosphocholine and 1,2-diacylglycerolphosphoglycerol. Isoform 2 and isoform 3 have lost catalytic activity.

Catalytic activity: Sphingomyelin + H2O = N-acylsphingosine + phosphocholine.

Subunit structure: Monomer.

Subcellular location: Lysosome.

Polymorphism: A common polymorphism arises from a variable number of hexanucleotide repeat sequence within the signal peptide region.

Involvement in disease: Niemann-Pick disease A (NPDA) [MIM:257200]: An early-onset lysosomal storage disorder caused by failure to hydrolyze sphingomyelin to ceramide. It results in the accumulation of sphingomyelin and other metabolically related lipids in reticuloendothelial and other cell types throughout the body, leading to cell death. Niemann-Pick disease type A is a primarily neurodegenerative disorder characterized by onset within the first year of life, mental retardation, digestive disorders, failure to thrive, major hepatosplenomegaly, and severe neurologic symptoms. The severe neurological disorders and pulmonary infections lead to an early death, often around the age of four. Clinical features are variable. A phenotypic continuum exists between type A (basic neurovisceral) and type B (purely visceral) forms of Niemann-Pick disease, and the intermediate types encompass a cluster of variants combining clinical features of both types A and B.Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.11 Ref.12 Ref.14 Ref.16 Ref.18 Ref.19 Ref.21 Ref.23 Ref.24 Ref.27 Ref.30 Ref.31Niemann-Pick disease B (NPDB) [MIM:607616]: A late-onset lysosomal storage disorder caused by failure to hydrolyze sphingomyelin to ceramide. It results in the accumulation of sphingomyelin and other metabolically related lipids in reticuloendothelial and other cell types throughout the body, leading to cell death. Clinical signs involve only visceral organs. The most constant sign is hepatosplenomegaly which can be associated with pulmonary symptoms. Patients remain free of neurologic manifestations. However, a phenotypic continuum exists between type A (basic neurovisceral) and type B (purely visceral) forms of Niemann-Pick disease, and the intermediate types encompass a cluster of variants combining clinical features of both types A and B. In Niemann-Pick disease type B, onset of the first symptoms occurs in early childhood and patients can survive into adulthood.Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.13 Ref.15 Ref.16 Ref.17 Ref.20 Ref.22 Ref.23 Ref.25 Ref.26 Ref.28 Ref.29 Ref.30 Ref.31 Ref.32

Miscellaneous: There are two types of sphingomyelinases: ASM (acid), and NSM (neutral).

Sequence similarities: Belongs to the acid sphingomyelinase family.Contains 1 saposin B-type domain.