Diacylglycerin

Diacylglycerin, also known as diacylglycerol (DAG), is a glycerol molecule with two fatty acid chains esterified to two of its hydroxyl groups, leaving one hydroxyl group free. The two main structural isomers are 1,2-diacylglycerol and 1,3-diacylglycerol, differing in which positions carry the esterified fatty acids.

DAG is a common intermediate in lipid metabolism. It can arise from the hydrolysis of triglycerides or phospholipids, and it is produced in cells by the action of phospholipase C on phosphatidylinositol 4,5-bisphosphate (PIP2), yielding DAG and inositol trisphosphate (IP3). DAG can be converted into triglycerides by diacylglycerol acyltransferase (DGAT) or phosphorylated to phosphatidic acid by DAG kinase, linking it to both energy storage and membrane lipid synthesis pathways.

In biology, DAG serves as a lipid second messenger. Within membranes, it activates certain isoforms of protein kinase C in a calcium-dependent manner, coordinating a wide range of cellular processes including proliferation, differentiation, and secretion. Its signaling role is tightly linked to its local concentration and the presence of calcium ions.

Industrially, DAGs are used as food emulsifiers and in the production of diacylglycerol oils, which are promoted as fat substitutes or healthier cooking fats in some markets. This use, along with their natural occurrence in foods and membranes, distinguishes DAG from triglycerides, which contain three fatty acids and function primarily as energy stores.