PG(22:5(4Z,7Z,10Z,13Z,16Z)/22:5(4Z,7Z,10Z,13Z,19Z)-O(16,17)) is an oxidized phosphatidylglycerol (PG). Oxidized phosphatidylglycerols 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 phosphatidylglycerols 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, phosphatidylglycerols 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. PG(22:5(4Z,7Z,10Z,13Z,16Z)/22:5(4Z,7Z,10Z,13Z,19Z)-O(16,17)), in particular, consists of one chain of one 4Z,7Z,10Z,13Z,16Z-docosapentaenoyl at the C-1 position and one chain of 16,17-epoxy-docosapentaenoyl 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 PGs can be synthesized via three different routes. In one route, the oxidized PG is synthetized de novo following the same mechanisms as for PGs 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 PG backbone, mainly through the action of LOX (PMID: 33329396 ).
