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Proteins/UNIPROT:P07602
Saposins are specific low-molecular mass non-enzymatic glycoproteins that act as activator proteins for lysosomal sphingolipid-degrading enzymes, facilitating the hydrolysis of sphingolipids by extracting lipid substrates from membranes and presenting them to their respective enzymes. They are derived from a common precursor protein, prosaposin, which is proteolytically cleaved to yield four homologous proteins (saposin A, B, C, and D), each with distinct but partially overlapping lipid and enzyme specificities..
[Prosaposin]: Behaves as a myelinotrophic and neurotrophic factor, these effects are mediated by its G protein-coupled receptors, GPR37 and GPR37L1, undergoing ligand-mediated internalization followed by ERK phosphorylation signaling..
[Saposin-A]: Acts as an essential lysosomal cofactor that activates galactocerebrosidase (GALC, EC 3.2.1.46) by facilitating enzyme access to its membrane-embedded galactosylceramide substrate, the principal lipid component of myelin..
[Saposin-B]: Stimulates the hydrolysis of galacto-cerebroside sulfate by arylsulfatase A ARSA (EC 3.1.6.8), GM1 gangliosides by beta-galactosidase (EC 3.2.1.23) and globotriaosylceramide by alpha-galactosidase A (EC 3.2.1.22). Forms a solubilizing complex with the substrates of the sphingolipid hydrolases..
[Saposin-C]: Acts as an essential lysosomal cofactor that activates acid beta-glucosylceramidases (EC 3.2.1.45) by altering lipid bilayer properties to facilitate enzyme access to its membrane-embedded glucosylceramide substrate, while also protecting glucocerebrosidase from intralysosomal proteolytic degradation..
[Saposin-D]: Acts as a lysosomal activator protein that stimulates acid ceramidase (EC 3.5.1.23) by solubilizing and presenting ceramide substrates at the lipid-water interface, facilitating their hydrolysis into sphingosine and fatty acids. It also activates acid sphingomyelinase (EC 3.1.4.12), though ceramide catabolism represents its primary physiological role..
Function from UniProtKB (P07602), read 2026-09-23. CC BY 4.0.
Curated compounds routed: 0
6 rows
105 statements
105 statements · 5 reference databases · Subject: PSAP · Sources: gene ontology, Hetionet, Human-GEM, Reactome, WikiPathways
3 reactions
water+a ganglioside GM1 (d18:1(4E))alpha-D-galactose+a ganglioside GM2 (d18:1(4E))
Catalysed by CTSA or GALNS or GLB1 or GM2A or PSAP or NEU1
Reaction pageLeft to rightBalance undeterminablelysosome
Human-GEM MAR12036CC BY 4.0Reference data
MAM01904l+watera ganglioside GA2 (d18:1(4E))
18 names
Resolves to: PSAP
Reaction pageLeft to rightBalance undeterminablelysosome
Human-GEM MAR12037CC BY 4.0Reference data
a globoside Gb3Cer (d18:1(4E))+wateralpha-D-galactose+MAM03586l
Reaction pageLeft to rightBalance undeterminableEC 3.2.1.22lysosome
Human-GEM MAR12053CC BY 4.0Reference data