摘要
The biosynthesis of glycolipids in E.fascicula-tus was studied by 14C label and chase. The fatty acids in sulphoquinovosyl diacylglycerol (SQDG) were almost 16-car-bon and 18-carbon ones. In addition to the two fatty acids, monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) contained 8.5 mol% and 31.0 mol% of eicosapentaenoic acid (20 : 5), respectively, and this fatty acid was usually distributed in the sn-1 position of the glyc-erol backbone. When plants were incubated with [2-14C] acetate, differences existed in the positional distribution of the labeled fatty acids in sn-1 and sn-2 among the three glycerolipids. In SQDG, 14C-labeled fatty acids were distributed uniformly in the sn-1 and sn-2 positions. In DGDG, 14C-labeled fatty acids were mainly distributed in the sn-2 position. In MGDG, the radioactivity of fatty acids in sn-1 position was far greater than that in sn-2 position after a 30 min pulse label, and the difference in radioactivity between the two positions
The biosynthesis of glycolipids in E. fasciculatus was studied by 14C label and chase. The fatty acids in sulphoquinovosyl diacylglycerol (SQDG) were almost 16-carbon and 18-carbon ones. In addition to the two fatty acids, monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) contained 8.5 mol% and 31.0 mol% of eicosapentaenoic acid (20: 5), respectively, and this fatty acid was usually distributed in the sn-1 position of the glycerol backbone. When plants were incubated with [2?14C] acetate, differences existed in the positional distribution of the labeled fatty acids in sn-1 and sn-2 among the three glycerolipids. In SQDG., 14C-labeled fatty acids were distributed uniformly in the sn-1 and sn-2 positions. In DGDG., 14C-labeled fatty acids were mainly distributed in the sn-2 position. In MGDG., the radioactivity of fatty acids in sn-1 position was far greater than that in sn-2 position after a 30 min pulse label, and the difference in radioactivity between the two positions decreased rapidly. The above results indicated that differences in the positional distribution of 14C-labeled fatty acids between sn-1 and sn-2 positions might be related to 20: 5 and the biosynthesis of DGDG. Our results also suggested that E. fasciculatus had the same DGDG biosynthetic pathway as that in higher plants and galactosyl transferase was selective for MGDG.
基金
This work was supportedby the National Natural Science Foundation of China (Grant No. 39890390), the One-Hundred-Scientist Program of the Chinese Academy of Sciences, the State Basic Research Development Plan of China (Grant No. G1998010100) and the I
