PSAP (Prosaposin): PSAP is a precursor protein that is processed into saposins, which are essential for breaking down lipids within lysosomes. These saposins play a crucial role in preventing the buildup of complex lipids in cells. Deficiencies or mutations in PSAP can result in lysosomal storage disorders, including Gaucher disease, Fabry disease, and metachromatic leukodystrophy.