MSI_000029598

PGP(a-13:0/i-22:0) is a phosphatidylglycerophosphate (PGP). It is a glycerophospholipid in which a phosphoglycerol moiety occupies a glycerol substitution site followed by another phosphate moiety. Phosphatidylglycerolphosphate is present at a level of 1-2\\% in most animal tissues, but it can be the second most abundant phospholipid in lung surfactant (up to 11\\% of the total). It is well established that the concentration of phosphatidylglycerolphosphate increases during fetal development. Phosphatidylglycerolphosphate may be present in animal tissues merely as a precursor for cardiolipin synthesis. As is the case with diacylglycerols, phosphatidylglycerophosphates can have many different combinations of fatty acids of varying lengths and saturation attached to the C-1 and C-2 positions. Fatty acids containing 16, 18 and 20 carbons are the most common. PGP(a-13:0/i-22:0), in particular, consists of one chain of anteisotridecanoic acid at the C-1 position and one chain of isodocosanoic acid at the C-2 position. They are synthesized by the addition of glycerol 3-phosphate to a CDP-diacylglycerol. In turn, PGPs are dephosphorylated to phosphatidylglycerols (PGs). While most phospholipids have a saturated fatty acid on C-1 and an unsaturated fatty acid on C-2 of the glycerol backbone, the fatty acid distribution at the C-1 and C-2 positions of glycerol within phospholipids is continually in flux, owing to phospholipid degradation and the continuous phospholipid remodeling that occurs while these molecules are in membranes.