Synthese van fosfatidylcholine in het ER-membraan

Glycerophospholipids, such as phosphatidylcholine, are one of the major components of eukaryotic cell membranes.

It is an important building block for new membranes during cell growth and division.

Additionally, it maintains membrane integrity and participates in cell signaling pathways.

Phosphatidylcholine is mainly synthesized in the ER using three primary reactants — free fatty acids, glycerol phosphate, and cytidine-diphosphocholine or CDP-choline, in the presence of enzymes embedded in the ER membrane.

As they are hydrophobic, free fatty acids use fatty acid-binding proteins to navigate through the cytosol. On reaching the ER membrane, they are activated by acyl-CoA ligase.

The membrane acyltransferase combines two activated fatty acids with glycerol phosphate to form a molecule of phosphatidic acid, which is inserted in the membrane.

Next, the phosphate head group of phosphatidic acid is removed by an enzyme phosphatase, converting phosphatidic acid into diacylglycerol.

Finally, choline phosphotransferase transfers the choline group from CDP-choline to diacylglycerol, resulting in a phosphatidylcholine molecule in the cytosolic leaflet of the ER membrane.