Lipid class distribution of highly unsaturated long chain fatty acids in marine dinoflagellates

The very long chain highly unsaturated C-28 fatty acids, octacosaheptaenoic [28:7(11-6)] and octacosaoctaenoic acid [28:8(n-3)], were found to be asso ciated with phospholipids, obtained by fractionation of total lipid extract s into distinct lipid classes, in 4 and 6, respectively, of 16 examined din oflagellates, An inter-fraction comparison of fatty acids associated with p hospholipids and glycolipids has also shown that the phospholipid fractions contained the majority (over 75% in 12 of 16 strains) of docosahexaenoic a cid [22:6(n-3)] and traces of tetracosanoic acid (24:0), By contrast, the h ighly unsaturated C-18 fatty acids octa-decatetraenoic [18:4(n-3)] and octa decapentaenoic acid [18:5(n-3)] were primarily recovered from a chloroplast -associated glycolipid fraction comprised of monogalactosyldiacylglycerol, digalactosyldiacylglycerol, and sulfoquinovosyldiacylglycerol. In 12 of 16 strains, an interfraction comparison showed that over 90% of 18:5(n-3) was found to be associated with glycolipids, These findings indicate that the C -28 fatty acids are located and probably synthesized in the cytoplasm or in an organelle other than the chloroplast, possibly with 22:6(n-3) and 24:0 as precursors, whereas the C-18 fatty acids 18:4(n-3) and 18:5(n-3) are gly colipid constituents apparently synthesized within the chloroplast, The fun ction(s) of these C-28 fatty acids as components of phospholipids in cellul ar membranes is currently unknown.