The PSAP gene encodes prosaposin, a precursor of four small nonenzymatic glycoproteins termed 'sphingolipid activator proteins' (SAPs) that assist in the lysosomal hydrolysis of sphingolipids. Saposins A-D localize primarily to the lysosomal compartment where they facilitate the catabolism of glycosphingolipids with short oligosaccharide groups. The precursor protein exists both as a secretory protein and as an integral membrane protein and has neurotrophic activities. Mutations in this gene have been associated with Gaucher disease and metachromatic leukodystrophy.
