Assay and inhibition of diacylglycerol lipase activity.

A series of N-formyl-α-amino acid esters of ß-lactone derivatives structurally related to tetrahydrolipstatin (THL) and O-3841 were synthesized that inhibit human and murine diacylglycerol lipase (DAGL) activities. New ether lipid reporter compounds were developed for an in vitro assay to efficiently screen inhibitors of 1,2-diacyl-sn-glycerol hydrolysis and related lipase activities using fluorescence resonance energy transfer (FRET). A standardized thin layer chromatography (TLC) radioassay of diacylglycerol lipase activity utilizing the labeled endogenous substrate [1″-(14)C]1-stearoyl-2-arachidonoyl-sn-glycerol with phosphorimaging detection was used to quantify inhibition by following formation of the initial product [1″-(14)C]2-arachidonoylglycerol and further hydrolysis under the assay conditions to [1-(14)C]arachidonic acid.

The preparation of 2-O-[1'-C]arachidonoyl-1-O-stearoyl-sn-glycerol.

2-O-Arachidonoyl-1-O-stearoyl-sn-glycerol is the most abundant molecular species of the 1,2-diacyl-sn-glycerol signaling lipids in neural tissue. The facile preparation of 2-O-[1'-(14)C]arachidonoyl-1-O-stearoyl-sn-glycerol from 2-O-[1'-(14)C]arachidonoyl-1-O-stearoyl-sn-glycero-3-phosphocholine at a hexane and phosphate buffer interface with phospholipase C was demonstrated on a 20 µCi scale in 83% radiochemical yield. The specific activity of the product 2-O-[1'-(14)C]arachidonoyl-1-O-stearoyl-sn-glycerol was 57.0 mCi/mmol and the radiochemical purity was determined to be >99% by TLC. The hydrolysis of this lipid biosynthetic intermediate with lipoprotein lipase was shown to produce 2-O-[1'-(14)C]arachidonoylglycerol (2-AG). The (14)C-radiolabeled monoacylglycerol 2-AG is an endogenous cannabinoid receptor-signaling molecule (endocannabinoid).