PGP(20:4(8Z,11Z,14Z,17Z)/22:6(4Z,7Z,11E,13Z,15E,19Z)-2OH(10S,17)) is an oxidized phosphoglycerophosphate (PGP). Oxidized phosphoglycerophosphates are glycerophospholipids in which a phosphoglycerol moiety occupies a glycerol substitution site and at least one of the fatty acyl chains has undergone oxidation. As all oxidized lipids, oxidized phosphoglycerophosphates belong to a group of biomolecules that have a role as signaling molecules. The biosynthesis of oxidized lipids is mediated by several enzymatic families, including cyclooxygenases (COX), lipoxygenases (LOX) and cytochrome P450s (CYP). Non-enzymatically oxidized lipids are produced by uncontrolled oxidation through free radicals and are considered harmful to human health (PMID: 33329396 ). As is the case with diacylglycerols, phosphoglycerophosphates can have many different combinations of fatty acids of varying lengths, saturation and degrees of oxidation attached at the C-1 and C-2 positions. PGP(20:4(8Z,11Z,14Z,17Z)/22:6(4Z,7Z,11E,13Z,15E,19Z)-2OH(10S,17)), in particular, consists of one chain of one 8Z,11Z,14Z,17Z-eicosapentaenoyl at the C-1 position and one chain of Protectin DX at the C-2 position. Phospholipids are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and signaling. Similarly to what occurs with phospholipids, the fatty acid distribution at the C-1 and C-2 positions of glycerol within oxidized phospholipids is continually in flux, owing to phospholipid degradation and the continuous phospholipid remodeling that occurs while these molecules are in membranes. Oxidized PGPs can be synthesized via three different routes. In one route, the oxidized PGP is synthetized de novo following the same mechanisms as for PGPs but incorporating oxidized acyl chains (PMID: 33329396 ). An alternative is the transacylation of one of the non-oxidized acyl chains with an oxidized acylCoA (PMID: 33329396 ). The third pathway results from the oxidation of the acyl chain while still attached to the PGP backbone, mainely through the action of LOX (PMID: 33329396 ).
