Monoacylglycerol lipase (MGL) is a 33 kDa serine hydrolase that catalyses the hydrolysis of monoacylglycerols to their corresponding fatty acids. The enzyme is found both in the brain and in peripheral tissues such as the kidney, ovary, testis, adrenal gland, adipose tissue and heart. The three-dimensional structure of MGL has been elucidated by X-ray crystallography, and the enzyme has been shown to be a dimeric molecule with amphitropic properties, that is, it can exist both in a soluble form and associated with the membrane lipid bilayers. Mutagenesis studies have demonstrated the importance of the catalytic triad of ser¹²², asp²³⁹ and his²⁶⁹ that the enzyme shares with other enzymes in the α/β hydrolase superfamily. The substrate is recruited via a wide hydrophobic tunnel, where it can then interact with the catalytic triad at the end of the tunnel.

MGL inhibitors have lagged behind, but have a potential advantage over FAAH inhibitors in terms of eCB specificity of action given that the N-acylethanolamines are a class of compounds with multiple biological actions.