PSAP The lysosomal degradation of sphingolipids takes place by the sequential action of specific hydrolases. Some of these enzymes require specific low-molecular mass, non-enzymic proteins: the sphingolipids activator proteins (coproteins). Defects in PSAP are the cause of combined saposin deficiency (CSAPD); also known as prosaposin deficiency. CSAPD is due to absence of all saposins, leading to a fatal storage disorder with hepatosplenomegaly and severe neurological involvement. Defects in PSAP saposin-B region are the cause of leukodystrophy metachromatic due to saposin-B deficiency (MLD- SAPB). MLD-SAPB is an atypical form of metachromatic leukodystrophy. It is characterized by tissue accumulation of cerebroside-3-sulfate, demyelination, periventricular white matter abnormalities, peripheral neuropathy. Additional neurological features include dysarthria, ataxic gait, psychomotr regression, seizures, cognitive decline and spastic quadriparesis. Defects in PSAP saposin-C region are the cause of atypical Gaucher disease (AGD). Affected individuals have marked glucosylceramide accumulation in the spleen without having a deficiency of glucosylceramide-beta glucosidase characteristic of classic Gaucher disease, a lysosomal storage disorder. Defects in PSAP saposin-A region are the cause of atypical Krabbe disease (AKRD). AKRD is a disorder of galactosylceramide metabolism. AKRD features include progressive encephalopathy and abnormal myelination in the cerebral white matter resembling Krabbe disease. Defects in PSAP saposin-D region are found in a variant of Tay-Sachs disease (GM2-gangliosidosis). 3 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Chromosomal Location of Human Ortholog: 10q22.1
Cellular Component:  azurophil granule membrane; extracellular region; extracellular space; intracellular membrane-bounded organelle; late endosome; lysosomal lumen; lysosomal membrane; lysosome; plasma membrane
Molecular Function:  beta-galactosidase activity; enzyme activator activity; G protein-coupled receptor binding; ganglioside GM1 binding; ganglioside GM2 binding; ganglioside GM3 binding; ganglioside GP1c binding; ganglioside GT1b binding; lipid binding; phospholipid binding; protease binding; protein binding; protein homodimerization activity
Biological Process:  cellular response to organic substance; cochlea development; corneocyte development; cornified envelope assembly; G protein-coupled receptor signaling pathway; galactosylceramide catabolic process; ganglioside GM1 transport to membrane; glycosphingolipid metabolic process; lipid transport; lysosomal transport; micturition; myelination; negative regulation of hydrogen peroxide-induced cell death; neuromuscular process controlling balance; neutrophil degranulation; platelet degranulation; positive regulation of hydrolase activity; positive regulation of MAPK cascade; regulation of autophagy; sensory perception of sound; walking behavior
Disease: Combined Saposin Deficiency; Gaucher Disease, Atypical, Due To Saposin C Deficiency; Krabbe Disease, Atypical, Due To Saposin A Deficiency; Metachromatic Leukodystrophy Due To Saposin B Deficiency
Reference #:  P07602 (UniProtKB)
Alt. Names/Synonyms: A1 activator; Cerebroside sulfate activator; Co-beta-glucosidase; Component C; CSAct; Dispersin; FLJ00245; GLBA; Glucosylceramidase activator; MGC110993; Proactivator polypeptide; Prosaposin; Protein A; Protein C; PSAP; SAP; SAP-1; SAP-2; SAP1; Saposin-A; Saposin-B; Saposin-B-Val; Saposin-C; Saposin-D; Sphingolipid activator protein 1; Sphingolipid activator protein 2; sphingolipid activator protein-1; Sulfatide/GM1 activator
Gene Symbols: PSAP
Molecular weight: 58,113 Da
Basal Isoelectric point: 5.06  Predict pI for various phosphorylation states
Select Structure to View Below


Protein Structure Not Found.

Cross-references to other databases:  STRING  |  cBioPortal  |  Wikipedia  |  Reactome  |  neXtProt  |  Protein Atlas  |  BioGPS  |  Pfam  |  RCSB PDB  |  Phospho3D  |  Phospho.ELM  |  GeneCards  |  UniProtKB  |  Entrez-Gene  |  GenPept  |  Ensembl Gene