Monoglyceride lipase-like enzymatic activity is responsible for hydrolysis of 2-arachidonoylglycerol in rat cerebellar membranes.
2-Arachidonoylglycerol (2-AG) is an endogenous cannabinoid that binds to CB1 and CB2 cannabinoid receptors, inducing cannabimimetic effects. However, the cannabimimetic effects of 2-AG are weak in vivo due to its rapid enzymatic hydrolysis. The enzymatic hydrolysis of 2-AG has been proposed to mainly occur by monoglyceride lipase (monoacylglycerol lipase). Fatty acid amide hydrolase (FAAH), the enzyme responsible for the hydrolysis of N-arachidonoylethanolamide (AEA), is also able to hydrolyse 2-AG. In the present study, we investigated the hydrolysis of endocannabinoids in rat cerebellar membranes and observed that enzymatic activity towards 2-AG was 50-fold higher than that towards AEA. Furthermore, various inhibitors for 2-AG hydrolase activity were studied in rat cerebellar membranes. 2-AG hydrolysis was inhibited by methyl arachidonylfluorophosphonate, hexadecylsulphonyl fluoride and phenylmethylsulphonyl fluoride with ic(50) values of 2.2 nM, 241 nM and 155 microM, respectively. Potent FAAH inhibitors, such as OL-53 and URB597, did not inhibit the hydrolysis of 2-AG, suggesting that 2-AG is inactivated in rat cerebellar membranes by an enzyme distinct of FAAH. The observation that the hydrolysis of 1(3)-AG and 2-AG occurred at equal rates supports the role of MGL in 2-AG inactivation. This enzyme assay provides a useful method for future inhibition studies of 2-AG degrading enzyme(s) in brain membrane preparation having considerably higher MGL-like activity when compared to FAAH activity.
Saario
Susanna M
SM
Department of Pharmaceutical Chemistry, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland. susanna.saario@uku.fi
Savinainen
Juha R
JR
Laitinen
Jarmo T
JT
Järvinen
Tomi
T
Niemi
Riku
R
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism*; D002186:Cannabinoids / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism*; D063388:Endocannabinoids; D005989:Glycerides / Q000378:metabolism*; D006868:Hydrolysis; D008297:Male; D008994:Monoacylglycerol Lipases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D001095:Arachidonic Acids; D002186:Cannabinoids; D063388:Endocannabinoids; D005989:Glycerides; C094503:glyceryl 2-arachidonate; D008994:Monoacylglycerol Lipases