diacylglycerolia

Diacylglycerol, commonly abbreviated as DAG, is a glycerol molecule esterified with two fatty acids. In its most common form, one fatty acid occupies the sn-1 position and another the sn-2 position of the glycerol backbone, leaving the hydroxyl group at sn-3 free; there are also positional isomers such as 1,3- and 2,3-DAG. DAG is an intermediate in lipid metabolism and a constituent of cellular membranes and lipid droplets.

Biological roles of DAG are twofold. It is an intermediate in the synthesis of triacylglycerol (TAG) via diacylglycerol acyltransferases, which add a third fatty acid to form TAG. DAG also functions as a lipid second messenger in signal transduction. Activation of certain phospholipase C enzymes cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) to yield inositol trisphosphate (IP3) and DAG; the membrane-associated DAG then activates protein kinase C and other target proteins. DAG can also be generated by lipolysis of TAG, and DAG lipase converts DAG to monoacylglycerol and fatty acids; 2-arachidonoylglycerol (2-AG), an endocannabinoid, is produced from DAG via this pathway.

Occurrence and dietary aspects of DAG are notable as well. DAG resides in cellular membranes and is a component of specialized dietary fats, known as diacylglycerol oils. These oils are used as food ingredients and have distinct metabolic effects, including altered fat absorption and postprandial lipid responses compared with traditional triglyceride-rich fats.

In summary, diacylglycerol is a versatile lipid involved in both lipid metabolism and cellular signaling, with relevance to physiology and nutrition.