In Vivo Incorporation of a Polyunsaturated Fatty Acid into the sn-C-1 and sn-C-2 Positions of Tetrahymena Glycerophospholipids1

The glycerophospholipids of the protozoon Tetrahymena pyriformis W are unique in that the polyunsaturated fatty acid γ-linolenate (18:3Δ^6,9,12) is a major component of both the sn-C-1 and sn-C-2 positions. Tetrahymena were incubated with 1-¹⁴C]γ-linolenate. The positional distribution of the radiolabeled fatty acid in the three major glycerophospholipids was determined. 1-¹⁴C]γ-linolenate was found at both carbons of the three lipids, in general agreement with the mass distribution of γ-linolenate, except for markedly greater labeling at the sn-C-2 position of phosphatidylcholine. We hypothesize that an acyltransferase exists in Tetrahymena that can esterify γ-linolenate at both carbons during glycerophospholipid biosynthesis.