Phosphatidylethanolamines (PE) are a class of phospholipids that incorporate a phosphoric acid headgroup into a diacylglycerol backbone. They are the second most abundant phospholipid in eukaryotic cell membranes, and contrary to phosphatidylcholine, it is concentrated with phosphatidylserine in the cell membrane's inner leaflet. In Homo sapiens, there exist two phosphatidylethanolamine biosynthesis pathways. In the visualization, all enzymes that are dark green in colour are membrane-localized. The first pathway synthesizes phosphatidylethanolamine from ethanolamine via the Kennedy pathway. First, the cytosol-localized enzyme choline/ethanolamine kinase catalyzes the conversion of choline into phosphocholine. Second, choline-phosphate cytidylyltransferase, localized to the endoplasmic reticulum membrane, catalyzes the conversion of phosphocholine to CDP-choline. Last, choline/ethanolaminephosphotransferase catalyzes phosphatidylcholine biosynthesis from CDP-choline. It requires either magnesium or manganese ions as cofactors. Phosphatidylethanolamine is also synthesized from phosphatidylserine at the mitochondrial inner membrane by phosphatidylserine decarboxylase. Phosphatidylserine, itself, is synthesized using a base-exchange reaction with phosphatidylcholine. This reaction is catalyzed by phosphatidylserine synthase which is located in the endoplasmic reticulum membrane.

Phosphatidylethanolamine Biosynthesis PE(22:6(4Z,7Z,10Z,13Z,16Z,19Z)/20:4(5Z,8Z,11Z,14Z)) References