1-Alkenyl group of ethanolamine plasmalogen derives mainly from de novo-synthesized fatty alcohol within peroxisomes, but not extraperoxisomal fatty alcohol or fatty acid.

Abstract

The origin of the 1-alkenyl group of ethanolamine plasmalogen was investigated. Three candidates were examined for the fatty alcohol forming the 1-alkenyl group. [1-(14)C]Hexadecanoic acid, [1-(14)C]hexadecanol, or [1-(14)C]lignoceric acid was administered to rats treated with 0.25% clofibrate-chow for 2 weeks. At 0.5, 1, 2, 3, and 4 h after administration of the radiolabeled compound, rats were killed and ethanolamine-containing phosphoglyceride (EPG)-rich fraction was isolated from the liver. The components of the 1-radyl group in EPG-rich fraction were separated and the radioactivity was determined. The radiolabel after administration of [1-(14)C]hexadecanoic acid or [1-(14)C]hexadecanol was almost wholly incorporated into diacyl-type glycerophosphoethanolamine (GPE), and was predominantly found in hexadecanoic acid fraction. Therefore, the long-chain fatty acid may be incorporated intact into the diacyl groups, and the long-chain fatty alcohol may be similarly incorporated after oxidation to the acid. In contrast, the radiolabel after the administration of [1-(14)C]lignoceric acid was found in the 1-alkenyl group of ethanolamine plasmalogen. After hydrolysis of the 1-alkenyl group by treatment of the plasmalogen with HCl vapor, the radiolabeled products were chiefly stearaldehyde and palmitaldehyde. The above data indicate that nascent fatty alcohol de novo synthesized from acetyl-CoA derived by peroxisomal beta-oxidation is almost exclusively used as the fatty alcohol forming the 1-alkenyl group of ethanolamine plasmalogen.