Acylglycerols, also known as glycerides or glycerolipids, are esters of glycerol with one, two, or three fatty acid molecules, forming the cornerstone of energy storage and membrane structure in biological systems.
Structural Classification
Acylglycerols are divided into three classes based on the degree of esterification: monoacylglycerols (MAGs) with one fatty acyl chain, diacylglycerols (DAGs) with two chains, and triacylglycerols (TAGs) with three chains. Glycerol's sn-1, sn-2, and sn-3 positions follow stereospecific numbering, with sn-1/sn-3 typically saturated (e.g., palmitic acid) and sn-2 polyunsaturated (e.g., oleic acid) in natural forms. The general formula is sn-glycero-3-phosphate derivatives, where R₁–₃ denote acyl chains varying in length (C4–C36), saturation, and configuration.
Biosynthesis
De novo synthesis via the glycerol-3-phosphate pathway begins with acylation of sn-glycerol-3-phosphate (from dihydroxyacetone phosphate) by acyltransferases (GPAT at sn-1, AGPAT at sn-2), yielding phosphatidic acid. Subsequent dephosphorylation produces DAGs, which are further acylated by DGAT to form TAGs. Fatty acyl-CoA or ACP serves as donors, with the Kennedy pathway recycling MAGs/DAGs from dietary lipids.
Physicochemical Properties
Acylglycerols exhibit hydrophobicity that drives micelle and lamellar self-assembly. Their melting points scale with saturation (TAGs 20–60°C), and they display polymorphism (α/β crystals affecting spreadability). MAGs and DAGs show amphiphilic properties as emulsifiers (HLB 3–6), while TAGs serve as energy stores (~9 kcal/g) with oxidative stability enhanced by antioxidants.
