acid ceramidase , other name: N-acylsphingosine deacylase; a lysosomal enzyme that catalyses the hydrolyis of ceramide to sphingosine and a fatty acid. Its activity requires sphingolipid activator proteins (i.e. saposins B and C) and negatively charged phospholipids. A genetic locus at 8p21.3-22 encodes a precursor that contains 395 amino acids and is proteolytically cleaved into an a subunit (≈13 kDa) and a β subunit (≈40 kDa) linked by a disulphide bridge. The b subunit is probably glycosylated. At least nine mutations in the gene are associated with various forms of a deficiency disease called Farber lipogranulomatosis. This is characterized by granuloma formation and lipid-laden macrophages in joints, subcutaneous tissue, larynx, and frequently also in liver, spleen, lungs, heart, and nervous system.
