ASAH3 (N-acylsphingosine amidohydrolase (alkaline ceramidase) 3), also designated ACER1, is a 264 amino acid multi-pass membrane protein that localizes to the membrane of the endoplasmic reticulum. Expressed predominately in epidermal tissue, ASAH3 catalyzes the hydrolysis of the sphingolipid ceramide into sphingosine and a free fatty acid, thereby playing an important role in the regulation of bioactive ceramide and sphingosine levels within the cell. ASAH3 functions at an optimal pH of 8.0 and has high specificity for the natural stereoisomer of ceramide with D-erythro-sphingosine, but not D-ribo-phytosphingosine or D-erythro-dihydrosphingosine as a backbone.