Positional distribution of fatty acids in the major glycerophospholipids of Paramecium tetraurelia

Abstract

Fatty acid positional distributions and the fatty acid compositions of diacyl and alkyl acyl analogs of the three major glycerophospholipids of Paramecium tetraurelia were examined. Phosphatidylcholine and the phospho- and phosphonyl ethanolamine glycerolipids were separated into diacyl and alkyl acyl species by thin-layer chromatography after phospholipase C digestion, and acetylation. Phosphatidylcholine and the ethanolamine phosphonolipid were predominantly in the alkyl acyl form and phosphatidylethanolamine was predominantly in the diacyl form. The three major glycerophospholipids were also subjected to hydrolysis by phospholipase A2. Complete and efficient hydrolyses of all three phospholipids were accomplished with the enzyme from porcine pancreas. Sodium tetraborate prevented acyl migration when added to reaction mixtures. Fatty acids released by phospholipase A2 action, and the lysoderivatives were separated by thin-layer chromatography. Fatty acid methyl esters were prepared and analyzed by gas-liquid chromatography. Saturated acids were predominantly at C-1 of diacyl phospholipids. Polyunsaturated fatty acids were mainly at C-2, particularly in the alkyl acyl species. An exception was gamma-linolenate which was a major acid found esterified to C-1 in the three diacyl phospholipids. Identification of this acid at that position supports the idea that in some ciliates there may be an acyltransferase, specific for gamma-linolenate, that esterifies this acid to the glycerophospholipids.