Fosfatidylcholin

Fosfatidylcholin, known in English as phosphatidylcholine, is a glycerophospholipid and a major structural component of biological membranes. Its molecule consists of a glycerol backbone with two fatty acid chains at the sn-1 and sn-2 positions, a phosphate group, and a choline head group. The choline moiety carries a quaternary ammonium, giving the molecule a zwitterionic character at physiological pH. Phosphatidylcholine is abundant in many membranes, including the plasma membrane and membranes of organelles, and is a key constituent of lipoproteins.

Biosynthesis and metabolic pathways occur primarily through the CDP-choline pathway (Kennedy pathway). In this route, choline is phosphorylated to phosphocholine by choline kinase, then converted to CDP-choline by CTP:phosphocholine cytidylyltransferase, and finally CDP-choline transfers its phosphocholine to diacylglycerol to form phosphatidylcholine via choline phosphotransferase. An alternative route in liver and some tissues involves sequential methylation of phosphatidylethanolamine by S-adenosylmethionine to produce phosphatidylcholine. Dietary choline can also contribute to cellular phosphatidylcholine synthesis and lipoprotein assembly.

Functions include providing a structural, fluid, and curved-forming component of membranes, facilitating lipoprotein assembly and secretion (notably very low-density lipoproteins), and supplying phosphatidylcholine for the pulmonary surfactant system in the lungs (where dipalmitoylphosphatidylcholine is especially important). Phosphatidylcholine is also a source of other phospholipids and diacylglycerol upon turnover. Dietary sources include egg yolk, soy, and lecithin preparations.