Positional distribution of fatty acids on the glycerol backbone during the biosynthesis of glycerolipids in Ectocarpus fasciculatus

The biosynthesis of glycolipids in E. fasciculatus 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 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.     

大鼠再生肝8种细胞的脂肪代谢基因转录谱预示的生化活动

为了解大鼠再生肝8种细胞的脂肪代谢基因转录谱及预示的生化活动,按张丽君[1]等方法分离大鼠再生肝的8种细胞,检测它们的脂肪代谢基因表达变化,分析其表达相关性及预示的代谢活动.结果表明,29个脂肪代谢相关基因在大鼠肝再生中发生了有意义的表达变化,8种细胞的相应基因个数为18、14、7、9、8、10、14、17.上调、下调和上/下调的基因个数为13、6和10,相应细胞的基因个数为10、8和0,12、2和0,5、2和0,5、3和1,5、2和1,8、2和0,8、6和0,10、7和0.8种肝脏细胞的脂肪分解相关基因表达增强.肝细胞、胆管上皮细胞、星形细胞、库普弗细胞、陷窝细胞、树突状细胞等6种细胞的脂肪合成相关基因表达增强.预示大鼠肝再生中脂肪代谢活动增强,与大鼠肝再生密切相关.