Depmeier_2022_Anal.Biochem__114889

1,2-Diacylglycerol lipases (DAGL) are the most important enzymes for the biosynthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG), and their role in various pathophysiological conditions is currently under investigation. We synthesized a new 1,2-diacylglycerol substrate for these enzymes with a fluorogenic 4-(pyren-1-yl)butanoyl residue in sn-2 position. Using the fluorescent substrate, we measured DAGL activity in rat liver S9 fraction and brain microsomes. To this end, 2-acylglycerol release was directly determined via HPLC and fluorescence detection without further sample clean-up. The method was used to evaluate the action of several known DAGL inhibitors. These showed partly significant differences in their inhibitory effect on DAGL enzymes in liver versus brain preparations. The method was verified by measuring the IC(50) values for a subset of inhibitors by HPLC and single-quad MS detection using the deuterated natural DAGL substrate 1-stearoyl-2-arachidonoyl-sn-glycerol-d(8). DAGL activity can also be measured with the new pyrene-labeled substrate by HPLC and UV instead of fluorescence detection, if larger quantities of the samples are injected into the HPLC system. Furthermore, using intact human sperm, we show that the substrate is also converted by DAGL enzymes in human cells.