Purity ~90% (SDS-PAGE). Saposin-A and saposin-C stimulate the hydrolysis of glucosylceramide by beta-glucosylceramidase and galactosylceramide by beta-galactosylceramidase. 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, GM1 gangliosides by beta-galactosidase and globotriaosylceramide by alpha-galactosidase A. Saposin-B forms a solubilizing complex with the substrates of the sphingolipid hydrolases. Saposin-D is a specific sphingomyelin phosphodiesterase activator. 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. Saposins are specific low-molecular mass non-enzymic proteins, they participate in the lysosomal degradation of sphingolipids, which take