Leondaritis G, Galanopoulou D
Department of Chemistry, University of Athens, Greece.
Lipids. 2000 May;35(5):525-32. doi: 10.1007/s11745-000-552-8.
The unicellular eukaryote Tetrahymena is a popular model for the study of lipid metabolism. Less attention, however, has been given to the inositol phospholipids of the cell, although it is known that this class of lipids plays an important role in eukaryotic cell signaling. Tetrahymena pyriformis phosphatidylinositol was isolated, purified, and characterized by proton nuclear magnetic resonance analysis and [2-(3)H]myoinositol labeling. Labeling was also used for polyphosphoinositide (phosphatidylinositol phosphate and phosphatidylinositol bisphosphate) identification. Tetrahymena inositol phospholipids were found to belong to the diacylglycerol group, although major Tetrahymena phospholipids, phosphatidylcholine and aminoethylphosphonoglycerides, have been found to be mainly alkylacylglyceroderivatives. Further characterization of Tetrahymena phosphatidylinositol by gas chromatographic analysis indicated that 80% of fatty acids were myristic acid and palmitic acid. This is also in contrast to the fatty acid profile of Tetrahymena phosphatidylcholine and phosphatidylethanolamine, with respect both to the fatty acid length and degree of unsaturation, and may indicate that specific diacylglycerol species are connected with the phosphatidylinositol metabolism in this cell. Treatment of [3H]inositol-labeled Tetrahymena cells with mastoparan, a G-protein-activating peptide, induced changes in the polyphosphoinositide levels, suggesting that inositol phospholipids may form in Tetrahymena a functional signaling system similar to that of higher eukaryotes. Addition of 10 microM mastoparan resulted in a rapid and transient increase in [3H]phosphatidylinositol phosphate followed by a decrease in [3H]phosphatidylinositol bisphosphate. Similar changes in lipids have been reported when phosphoinositide-phospholipase C pathway is activated in both animal and plant cells.
单细胞真核生物四膜虫是脂质代谢研究的常用模型。然而，细胞中的肌醇磷脂受到的关注较少，尽管已知这类脂质在真核细胞信号传导中起重要作用。通过质子核磁共振分析和[2-(3)H]肌醇标记对梨形四膜虫磷脂酰肌醇进行了分离、纯化和表征。标记还用于多磷酸肌醇（磷脂酰肌醇磷酸和磷脂酰肌醇二磷酸）的鉴定。发现四膜虫肌醇磷脂属于二酰基甘油类，尽管已发现四膜虫的主要磷脂磷脂酰胆碱和氨乙基磷脂酰甘油主要是烷基酰基甘油衍生物。通过气相色谱分析对四膜虫磷脂酰肌醇进行的进一步表征表明，80%的脂肪酸是肉豆蔻酸和棕榈酸。这也与四膜虫磷脂酰胆碱和磷脂酰乙醇胺的脂肪酸谱在脂肪酸长度和不饱和度方面形成对比，可能表明特定的二酰基甘油种类与该细胞中的磷脂酰肌醇代谢有关。用一种G蛋白激活肽——mastoparan处理[3H]肌醇标记的四膜虫细胞，会引起多磷酸肌醇水平的变化，这表明肌醇磷脂可能在四膜虫中形成类似于高等真核生物的功能性信号系统。添加10微摩尔的mastoparan会导致[3H]磷脂酰肌醇磷酸迅速短暂增加，随后[3H]磷脂酰肌醇二磷酸减少。当动物和植物细胞中的磷脂酰肌醇-磷脂酶C途径被激活时，也报道了脂质的类似变化。
