Phosphatidylethanolamine

Preparation

Currently, the exact substance regulating the conversion of diacylglycerol to phosphatidylcholine, phosphatidylethanolamine, or triacylglycerol is not fully understood. In hepatocytes, yeast, and certain bacteria, a pathway for the conversion of phosphatidylethanolamine to phosphatidylcholine has been found. In this pathway, which involves three consecutive reactions, a methyl group is transferred from S-adenosylmethionine (AdoMet) to phosphatidylethanolamine. This transfer process is catalyzed by phosphatidylethanolamine-N-methyltransferase located on the endoplasmic reticulum. Through the methylation of phosphatidylethanolamine, hepatocytes achieve interconversion between phosphatidylcholine and phosphatidylethanolamine, indirectly producing choline. The remaining four major phospholipids in eukaryotic cells are synthesized from CDP diacylglycerols in a manner similar to the synthesis of phosphatidylcholine and phosphatidylethanolamine. For example, phosphatidylserine can be obtained by the reaction of CDP diacylglycerols with serine catalyzed by phosphatidylserine synthase, or by the base exchange reaction of phosphatidylethanolamine with serine. Phosphatidylinositol can be obtained by the reaction of CDP diacylglycerols with L-inositol catalyzed by phosphatidylinositol synthase.

Uses

L-α-Phosphatidylethanolamine from egg yolk has been used:

• as a component of lipid mixture for the synthesis of giant unilamellar vesicles (GUVs)
• in ceramide phosphoethanolamine (CPE) synthase assay using crude sphingomyelin synthase-related protein from Hela cells
• for the standard curve generation for the quantification of lipids in plantaris muscle homogenates from mice

General Description

L-α-Phosphatidylethanolamine from egg yolk has high unsaturated fatty acid content and elicits radical-scavenging activity. L-α-Phosphatidylethanolamine (PE) is a membrane phospholipid and is interconverted to phosphotidylserine in the presence of phosphatidylserine synthase 2. PE is essential for maintaining the structural integrity of membranes. It is the second most abundant phospholipid in animals, plants and yeast and the major lipid in bacteria. It is synthesized in mitochondria in mammals.

Enzyme inhibitor

This hygroscopic phospholipid, also called cephalin and 1,2-diacyl-snglycero- 3-phosphoethanolamine, is an important constituent of biomembranes and lipoproteins. It is the major structural phospholipid in brain tissue. The physical properties depend on the nature of the acyl groups and on the presence of other lipids. Freshly prepared phosphatidylethanolamines are white solids that turn yellow and brown on exposure to air. They typically sinter between 80 and 90°C and melt in the neighborhood of 175°C. Solutions of phosphatidylethanolamine slowly decompose at room temperature (roughly 0.3-0.5% per day); hence, solutions should always be freshly prepared and kept cold prior to use. It is labile in alkaline conditions. See also specific compound Target(s): b- N-acetylglucosaminyl-glycopeptide b-1,4-galactosyltransferase; Nacetyllactosamine synthase; acylglycerol kinase, or monoacylglycerol kinase; cholesterol monooxygenase, side-chain-cleaving, or CYP11A1; chymase; cytidylate cyclase; dolichyldiphosphatase; dolichyl-phosphatase; dopamine b-monooxygenase; ethanolaminephosphotransferase; glutamate dehydrogenase; γ-glutamyl transpeptidase, mildly inhibited; glycerol-3-phosphate Oacyltransferase; glycerone-phosphate O-acyltransferase, or dihydroxyacetione-phosphate O-acyltransferase; hormone-sensitive lipase; 3-hydroxybutyrate dehydrogenase; indole-3-acetate b-glucosyltransferase; phosphatidate cytidylyltransferase; 1- phosphatidylinositol 4-kinase; phosphoinositide phospholipase C; phospholipase D, phosphatidylcholine-specific enzyme; sphingomyelin phosphodiesterase; steryl-b-glucosidase; UDP-Nacetylglucosamine: dolichyl-phosphate N-acetylglucosaminephosphotransferase.

Purification Methods

Purify the cephalin by dissolving it in EtOH, adding Pb(OAc)2.3H3O (30g in 100mL H2O) until excess Pb2+ is present. Filter off the solid. Pass CO2 gas through the solution until precipitation of PbCO3 ceases. Filter the solid off and evaporate (while bubbling CO2) under vacuum. An equal volume of H2O is added to the residual oil and extracted with hexane. The hexane extract is washed with H2O until the aqueous phase is free from Pb [test with dithizone (2 mg in 100 mL CCl4; Feigel Spot Tests Vol I, Elsevier p. 10 1954)]. The hexane is dried (Na2SO4), filtered and evaporated to give a yellow waxy solid which should be dried to constant weight in vacuo. It is practically insoluble in H2O and Me2CO, but freely soluble in CHCl3 (5%) and Et2O, and slightly soluble in EtOH. [Schofield & Dutton Biochemical Preparations 5 5 1957.]