Acid ceramidase catalyzes the degradation of ceramide in normal tissues, and deficiency leads to accumulation of ceramide in tissues, a hallmark of Farber disease. Effected individuals experience early onset joint problems and neurological problems, owing to mutations in the acid ceramidase gene. Bioinformatic analysis of gene expression also reveals acid ceramidase to be among the 5 most important genes associated with melanoma. In addition to ceramide hydrolysis, purified acid ceramidase also exhibits the ability to catalyze ceramide synthesis, utilizing [14C]lauric acid and sphingosine as substrates. Interestingly, pH regulates which reaction is favored; for hydrolysis the pH optimum is 4.5, whereas for the reverse reaction favors a pH of 5.5, further supporting a complex and central role for acid ceramidase in sphingolipid metabolism.