Plasmalogen Biosynthesis in Ehrlich Ascites Cells Grown in Tissue Culture

Abstract

1-14C-1-3H-Hexadecanol was incubated with Ehrlich ascites cells grown in tissue culture for 6, 12, 24, 36, and 48 hours. The distribution of radioactivity, specific radioactivities, and 3H:14C ratios of the acyl, alkyl, and alk-1-enyl moieties derived from glyceryl ether diesters, phosphatidylcholines, and phosphatidylethanolamines were determined and compared. All of the labeled alcohol disappeared within 12 hours and 65 to 85% of the administered radioactivity was incorporated into the lipids of the cell. The radioactivity was selectively incorporated into the glyceryl ethers of glyceryl ether diesters, phosphatidylcholine, and phosphatidylethanolamine. The percentage of radioactivity in the alkyl glyceryl ethers of the phosphatidylethanolamine decreased with increased incubation time, and the alk-1-enyl glyceryl ethers showed a corresponding increase in the percentage of radioactivity. Total and specific radioactivities strongly suggest a product-precursor relationship between the alkyl and alk-1-enyl glyceryl ethers, as our earlier data suggested. The alk-1-enyl acyl phosphoglyceride (plasmalogen) appears to arise by dehydrogenation of the intact alkyl acyl phosphoglycerides. The data also indicate that the origin of acyl and alkyl moieties of phosphatidylcholine is different from the origin of these moieties used in the biosynthesis of phosphatidylethanolamine. An unidentified radioactive lipid fraction, containing possible intermediates of alkyl glyceryl ether biosynthesis, was isolated from the media and partially characterized.