Monoacylglycerols (MAGs), also known as monoglycerides, are amphipathic lipids consisting of glycerol esterified with a single fatty acid chain. They serve as key intermediates in lipid digestion, emulsification, and cellular signaling.
Chemical Structure
MAGs feature a three-carbon glycerol backbone with one hydroxyl group esterified to a fatty acyl chain (typically C8-C18, saturated or unsaturated) via an ester bond, yielding two positional isomers: 1(3)-monoacyl-sn-glycerols (primary position, ~90% in equilibrium) and 2-monoacyl-sn-glycerol (secondary position). General formula: C₃H₈O₃-RCOO, where R denotes the alkyl chain (e.g., 1-monopalmitin: CH₂OH-CHOH-CH₂OCOC₁₅H₃₁). The polar head (two free -OH groups) and hydrophobic tail confer surfactant properties (HLB 3.5-6.0).
Biosynthesis and Metabolism
MAGs arise primarily from partial hydrolysis of triacylglycerols (TAGs) by pancreatic or lipoprotein lipases at intestinal sn-1/sn-3 positions, or via diacylglycerol lipase action in cells. Endogenous synthesis utilizes acyl-CoA:glycerol acyltransferase (sn-1 preference). They undergo rapid re-esterification to TAGs (2-MAG pathway) or absorption into enterocytes, with 2-MAG isomerizing to 1-MAG via acyl migration (half-life ~30 s).
Physicochemical Properties
MAGs exhibit high water solubility compared to di-/triacylglycerols (forming liquid crystals, micelles, or lamellar phases), melting points of 35-60°C (dependent on chain length/saturation), and emulsifying capacity via mesophase formation (α-gel, cubic, hexagonal). They resist oxidation better than unsaturated fatty acids alone and display antimicrobial activity against Gram-positives via membrane disruption.
