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AC_NAAA This conserved domain includes two closely related proteins, acid ceramidase (AC, also known as N-acylsphingosine amidohydrolase), and N-acylethanolamine-hydrolyzing acid amidase (NAAA). AC catalyzes the hydrolysis of ceramide to sphingosine and fatty acid. Ceramide is required for the biosynthesis of most sphingolipids and plays an important role in many signal transduction pathways by inducing apoptosis and/or arresting cell growth. An inherited deficiency of AC activity leads to the lysosomal storage disorder known as Farber disease. AC is considered a "rheostat" important for maintaining the proper intracellular levels of these lipids since hydrolysis of ceramide is the only source of sphingosine in cells. NAAA is a eukaryotic glycoprotein that hydrolyzes bioactive N-acylethanolamines, including anandamide (an endocannabinoid) and N-palmitoylethanolamine (an anti-inflammatory and neuroprotective substance), to fatty acids and ethanolamine at acidic pH. NAAA shows structural and functional similarity to acid ceramidase, but lacks the ceramide-hydrolyzing activity of AC.
Jiyao W et al.(2023). "The conserved domain database in 2023.",