diacyl

Diacyl is a chemical descriptor used for molecules that contain two acyl groups, typically two covalently attached acyl substituents derived from carboxylic acids, connected to a core backbone by ester or amide linkages. The term is commonly used in lipid chemistry and biochemistry to distinguish diacyl species from monoacyl and triacyl analogues.

In lipid chemistry, diacyl refers to molecules such as diacylglycerols, where two fatty acid chains are esterified to a glycerol backbone. Diacylglycerols (DAGs) usually have fatty acids at the sn-1 and sn-2 positions and vary in chain length and degree of unsaturation. DAG is an important intermediate in the metabolism of lipids and, in cellular signaling, a diacylglycerol molecule functions as a second messenger that can activate protein kinase C (PKC) enzymes at membranes. DAG can be produced by the hydrolysis of phospholipids, such as phosphatidylcholine or phosphatidylinositol bisphosphate, through specific phospholipase enzymes, or by lipolysis of diacylglycerol esters.

Other diacyl species include diacyl phospholipids, which consist of two fatty acyl chains plus a polar head group and a phosphate, as found in many glycerophospholipids. The term also applies more broadly to any compound bearing two acyl groups, such as diacyl esters formed when a diol is esterified with two carboxylic acid derivatives.

Overall, diacyl denotes a class of compounds defined by two acyl groups attached to a common molecular framework, with particular prominence in lipid structure and signaling.