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

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-UC]-Hexadecanoic acid, [l-14C]hexadecanol, or [l-uC]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 phospho-glyceride (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 [l-uC]hexadecanoic acid or [l-MC]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 [l-14C]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 HC1 vapor, the radiolabeled products were chiefly stearaldehyde and palmitaldehyde. Th