Kaneshiro E S, Jayasimhulu K, Sul D, Erwin J A
Department of Biological Sciences, University of Cincinnati, OH 45221, USA.
J Lipid Res. 1997 Dec;38(12):2399-410.
Paremecium tetraurelia contains high concentrations of six ethanolamine sphingolipids in the cell surface membrane surrounding somatic cilia. Three have phosphoryl groups and the other three have phosphonyl groups, and each contains either dihydrosphingosine, sphingosine, or phytosphingosine. In the present study, free, phosphorylated, and three major glycosylated ceramides were identified in the neutral sphingolipid fraction of this organism when it was grown on a crude medium. Individual lipids were characterized by specific staining on thin-layer chromatographic plates and the fatty acids derived from them were identified by gas-liquid chromatography and mass spectrometry. Unlike the esterified fatty acid composition of the ciliate's phospholipids, which have only small amounts of fatty acids greater than 20 carbons in length, the neutral sphingolipids mainly contain fatty acids greater than 22 carbons in length as well as high concentrations of long chain hydroxy fatty acids. The sugars, glucose, galactose, and fructose, were identified in total neutral sphingolipid fraction. The long chain bases in the neutral sphingolipid fraction were mainly C18 compounds and were identified as C18 dihydrosphingosine, C20 sphingosine, and isomers of C18 sphingosine. Phytosphingosine was not detected in the neutral sphingolipid fraction obtained from whole cells. Because most of the cell's phytosphingosine-containing ethanolamine sphingolipids are in cilia, the inability to detect phytosphingosine as part of putative precursor ceramide compounds suggests that conversions of the long chain base moiety of ethanolamine phospho- and phosphonosphingolipids occur in situ in the ciliary membrane.
四膜虫在体纤毛周围的细胞表面膜中含有高浓度的六种乙醇胺鞘脂。其中三种含有磷酸基团，另外三种含有膦酰基团，并且每种都含有二氢鞘氨醇、鞘氨醇或植物鞘氨醇。在本研究中，当该生物体在粗培养基上生长时，在其中性鞘脂部分中鉴定出了游离的、磷酸化的和三种主要的糖基化神经酰胺。通过薄层色谱板上的特异性染色对单个脂质进行表征，并通过气相色谱和质谱对衍生自它们的脂肪酸进行鉴定。与纤毛虫磷脂的酯化脂肪酸组成不同，纤毛虫磷脂中只有少量长度大于20个碳的脂肪酸，而中性鞘脂主要含有长度大于22个碳的脂肪酸以及高浓度的长链羟基脂肪酸。在总中性鞘脂部分中鉴定出了糖、葡萄糖、半乳糖和果糖。中性鞘脂部分中的长链碱基主要是C18化合物，被鉴定为C18二氢鞘氨醇、C20鞘氨醇和C18鞘氨醇的异构体。在从全细胞获得的中性鞘脂部分中未检测到植物鞘氨醇。由于细胞中大多数含植物鞘氨醇的乙醇胺鞘脂都在纤毛中，无法检测到植物鞘氨醇作为假定前体神经酰胺化合物的一部分，这表明乙醇胺磷酸鞘脂和膦酰鞘脂的长链碱基部分的转化发生在纤毛膜原位。
