LIPIDS OF ECTOCARPUS-FASCICULATUS (PHAEOPHYCEAE) - INCORPORATION OF [1-C-14]OLEATE AND THE ROLE OF TAG AND MGDG IN LIPID-METABOLISM

Lipids and fatty acids of Ectocarpus fasciculatus (Ectocarpales, Phaeo phyceae) were analyzed, Major polar lipids are monogalactosyldiacylgly cerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacyl glycerol (SQDG), glycerylhydroxymethyl-N,N,N-trimethyl-beta-alanine (D GTA), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phospha tidylglycerol (PG) and phosphatidylinositol (PI). Diphosphatidylglycer ol (DPG), phosphatidic acid (PA) and phosphatidyl-O-[N-(2-hydroxyethyl )glycine] (PHEG) were also present in small amounts, Nonpolar lipids m ainly consist of triacylglycerol (TAG) and diacylglycerol (DAG), Major fatty acids are 16:0, 18:1, alpha 18:3, 18:4, 20:4 and 20:5, The posi tional distribution of fatty acids showed that molecular species of eu karyotic structure account for 99% in MGDG, 98% in DGDG, 62% in PG and 23% in SQDG, On incubation with [1-C-14]18:1 for 30 min, 33% of the t otal label was detected in TAG, 16% in PG, 14% in PE, 10% in PC and 8% in MGDG, During 7 days of chase, the label in TAG, PG, PE and PC decr eased and simultaneously increased in MGDG up to 41% of the total, In SQDG, labelled fatty acids were found in prokaryotic as well as in euk aryotic molecular species, During the experiment, the label shifted fr om 18:1 to 18:2, 18:3, 18:4 and, to a minor extent, to 20:4 and 20:5 a cids indicating 18:1 to be processed by elongation and/or desaturation , These results suggest TAG to act as a major primary acceptor of exog enous oleate and to be involved in the transfer of fatty acids to MGDG and other polar lipids.