MSI_000060132

PG(18:3(6Z,9Z,12Z)/16:0) is a phosphatidylglycerol or glycerophospholipid (PG or GP). It is a glycerophospholipid in which a phosphoglycerol moiety occupies a glycerol substitution site. As is the case with diacylglycerols, phosphatidylglycerols can have many different combinations of fatty acids of varying lengths and saturation attached at the C-1 and C-2 positions. Fatty acids containing 16, 18 and 20 carbons are the most common. PG(18:3(6Z,9Z,12Z)/16:0), in particular, consists of one chain of g-linolenic acid at the C-1 position and one chain of palmitic acid at the C-2 position. The g-linolenic acid moiety is derived from animal fats, while the palmitic acid moiety is derived from fish oils, milk fats, vegetable oils and animal fats. Phosphatidylglycerol is present at a level of 1-2\\% in most animal tissues, but it can be the second most abundant phospholipid in lung surfactant at up to 11\\% of the total. It is well established that the concentration of phosphatidylglycerol increases during fetal development. Phosphatidylglycerol may be present in animal tissues merely as a precursor for diphosphatidylglycerol (cardiolipin). Phosphatidylglycerol is formed from phosphatidic acid by a sequence of enzymatic reactions that proceeds via the intermediate, cytidine diphosphate diacylglycerol (CDP-diacylglycerol). Bioynthesis proceeds by condensation of phosphatidic acid and cytidine triphosphate with elimination of pyrophosphate via the action of phosphatidate cytidyltransferase (or CDP-synthase). CDP-diacylglycerol then reacts with glycerol-3-phosphate via phosphatidylglycerophosphate synthase to form 3-sn-phosphatidyl-1-sn-glycerol 3-phosphoric acid, with the release of cytidine monophosphate (CMP). Finally, phosphatidylglycerol is formed by the action of specific phosphatases. 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. PGs have a net charge of -1 at physiological pH and are found in high concentration in mitochondrial membranes and as components of pulmonary surfactant. PG also serves as a precursor for the synthesis of cardiolipin. PG is synthesized from CDP-diacylglycerol and glycerol-3-phosphate. PG(18:3(6Z,9Z,12Z)/16:0) is a phosphatidylglycerol. Phosphatidylglycerols consist of a glycerol 3-phosphate backbone esterified to either saturated or unsaturated fatty acids on carbons 1 and 2. As is the case with diacylglycerols, phosphatidylglycerols can have many different combinations of fatty acids of varying lengths and saturation attached to the C-1 and C-2 positions. PG(18:3(6Z,9Z,12Z)/16:0), in particular, consists of one 6Z,9Z,12Z-octadecatrienoyl chain to the C-1 atom, and one hexadecanoyl to the C-2 atom. In E. coli glycerophospholipid metabolism, phosphatidylglycerol is formed from phosphatidic acid (1,2-diacyl-sn-glycerol 3-phosphate) by a sequence of enzymatic reactions that proceeds via two intermediates, cytidine diphosphate diacylglycerol (CDP-diacylglycerol) and phosphatidylglycerophosphate (PGP, a phosphorylated phosphatidylglycerol). Phosphatidylglycerols, along with CDP-diacylglycerol, also serve as precursor molecules for the synthesis of cardiolipin, a phospholipid found in membranes.