Fatty acid amide hydrolase (FAAH), belonging to an amidase-signature (AS) protein family, is a membrane-bound protein predominantly in microsomal and mitochondrial fractions that catalyzes the hydrolysis of several bioactive lipids, including anandamide, 2-arachidonoylglycerol (2-AG) and oleamide. The mammalian FAAHs are 63 kDa (579 amino acids in length) proteins characterized by containing several domains defined by homology and function, including, a highly conserved seine-and-glycine-rich AS domain, a predicted transmembrane domain and a proline rich domain. Results of mutation studies suggest, unlike other members of AS protein family, the catalytic activity of FAAH is not associated with the Ser-His-Asp triad but possibly with Ser217 and Lys142.