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Phosphatidylethanolamine (PE) is a phospholipid found in cell and organelle membranes, abundant in the brain and nervous tissue. It plays a role in cognition and memory, stabilizing membranes, hepatic secretion, and membrane fission and fusion. Cephalin, a type of PE, is believed to contribute significantly to neural tissues. Supplements containing cephalin are available, but their effectiveness is uncertain.
Phosphatidylethanolamine (PE) is an important phospholipid that makes up cell membranes and organelle membranes. It is also called cephalin because it is abundant in the brain, spinal cord and other nervous tissue. As many as 45% of brain phospholipids are made up of cephalin. Cephalin is believed to play an important role in cognition and memory. In bacteria, phosphatidylethanolamine is the major phospholipid; in animals, lecithin or phosphatidylcholine is most abundant, but cephalin is close second.
Like phosphatidylcholine, phosphatidylethanolamine is composed of glycerol, two fatty acids, and phosphoric acid. While phosphatidylcholine has choline attached to the phosphate group, PE has ethanolamine. The fatty acids in PE can be identical or different, but usually occupy the 1,2 carbon positions. Sometimes, however, they can occupy the 1.3 carbon positions.
Animals and humans obtain most of the ethanolamine moiety of PE from food sources. The body then produces phosphatidylethanolamine through a series of enzymatic steps. First, ethanolamine is phosphorylated by a cytosolic enzyme called ethanolamine kinase. Second, the product of the first reaction is combined with cytidine triphosphate to create cytidine ethanolamine phosphotransferase. Finally, an endoplasmic reticulum membrane-bound enzyme called cytidine diphospho-ethanolamine:diacylglycerol ethanolamine phosphotransferase acts on the product of the second reaction and diacylglycerol to form PE.
The melting point of phosphatidylcholine is -20 degrees Celsius, while that of phosphatidylethanolamine is -16 degrees Celsius. PE has a higher melting point, so it is less fluid. Phosphatidylethanolamine is thought to lend lateral pressure to the lipid bilayer, such that membrane proteins achieve their stable confirmation. It is also believed to support the placement of positively charged amino acids within the membrane.
Phosphatidylethanolamine has many other biological roles. It helps stabilize the sarcolemma membranes of heart tissue when there is an inadequate supply of oxygen, as occurs in coronary artery disease. PE also plays a role in hepatic secretion of very low density lipoproteins as well as membrane fission and fusion. It undergoes reactions to donate its ethanolamine component for the production of a membrane protein anchor compound called glycosylphosphatidylinositol. PE can also be converted to phosphatidylcholine by phosphatidyl ethanolamine methyltransferase, an enzyme found in the liver.
Cephalin is hypothesized to play a major role in keeping the nervous system intact and healthy due to its multitude of functions and its significant contribution to neural tissues. Some supplements containing this phospholipid are available on the market. There is no solid basis as to the effectiveness of these supplements in maintaining and restoring nervous system health, or in serving as memory enhancers.
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