PSAP Antibody - #DF4331

Saposin-A and saposin-C stimulate the hydrolysis of glucosylceramide by beta-glucosylceramidase (EC 3.2.1.45) and galactosylceramide by beta-galactosylceramidase (EC 3.2.1.46). Saposin-C apparently acts by combining with the enzyme and acidic lipid to form an activated complex, rather than by solubilizing the substrate.

Saposin-B stimulates the hydrolysis of galacto-cerebroside sulfate by arylsulfatase A (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). Saposin-B forms a solubilizing complex with the substrates of the sphingolipid hydrolases.

Saposin-D is a specific sphingomyelin phosphodiesterase activator (EC 3.1.4.12).

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.

Saposins are specific low-molecular mass non-enzymic proteins, they participate in the lysosomal degradation of sphingolipids, which takes place by the sequential action of specific hydrolases.

The lysosomal precursor is proteolytically processed to 4 small peptides, which are similar to each other and are sphingolipid hydrolase activator proteins.

N-linked glycans show a high degree of microheterogeneity.

The one residue extended Saposin-B-Val is only found in 5% of the chains.

Lysosome.

Secreted.
Note: Secreted as a fully glycosylated 70 kDa protein composed of complex glycans.

Saposin-B is a homodimer. Prosaposin exists as a roughly half-half mixture of monomers and disulfide-linked dimers. Monomeric prosaposin interacts (via C-terminus) with sortilin/SORT1, the interaction is required for targeting to lysosomes. Interacts with GRN; facilitates lysosomal delivery of progranulin from the extracellular space and the biosynthetic pathway.