Kennedy E P, Rumley M K, Schulman H, Van Golde L M
J Biol Chem. 1976 Jul 25;251(14):4208-13.
A previous report from this laboratory (van Golde, L.M.G., Schulman, H., and Kennedy, E.P. (1973) Proc. Natl. Acad. Sci. U.S.A. 70, 1368-1372) described the discovery in Escherichia coli of a novel class of oligosaccharides, containing glucose as the sole sugar, substituted with glycerophosphate units derived from membrane phospholipids, and with succinic acid in O-ester linkage. These membrane-derived oligosaccharides, comprising about 0.5 to 1.0% of the dry weight of E. coli, represent a family of closely related oligosaccharides that may be subfractionated on anion exchange resins. The present paper describes studies of the oligosaccharide A-1 described by van Golde et al. in the previous report. The glycerophosphate linked to the oligosaccharide in phosphodiester bond is the sn-glycero-1-P enantiomer. This finding strongly supports the previous conclusion that the oligosaccharides are the acceptors of the polar headgroups of membrane phospholipids, since the unesterified glycerophosphate of phosphatidyl glycerol is an sn-glycero-1-P residue, otherwise rare in nature. The glycerophosphate residues in the membrane-derived oligosaccharide are not substituted in the sn-2 or sn-3 positions, since they are readily oxidized by periodate under mild conditions. Alkaline hydrolysis liberates glycerophosphate, and only negligible amounts of free glycerol, consistent with the view that the glycerophosphate residues are linked to glucose units through position 6, unfavorable for the formation of glucose cyclic phosphate intermediates that would eliminate free glycerol. Oligosaccharide A-1 (but not Fraction A-2) contains phosphoethanolamine residues equivalent to 30 to 40% of the total phosphorus. The phosphoethanolamine residues are linked to position 6 of glucose units, as proved by the isolation of glucose 6-phosphate as a product of partial acid hydrolysis.
本实验室之前的一份报告（范·戈尔德，L.M.G.，舒尔曼，H.，以及肯尼迪，E.P.（1973年）《美国国家科学院院刊》70，1368 - 1372）描述了在大肠杆菌中发现的一类新型寡糖，这类寡糖仅含葡萄糖作为唯一糖类，被源自膜磷脂的甘油磷酸单元取代，且在O - 酯键处含有琥珀酸。这些膜衍生寡糖约占大肠杆菌干重的0.5%至1.0%，代表了一类密切相关的寡糖家族，可在阴离子交换树脂上进行细分。本文描述了范·戈尔德等人在前一份报告中所描述的寡糖A - 1的研究。以磷酸二酯键与寡糖相连的甘油磷酸是sn - 甘油 - 1 - P对映体。这一发现有力地支持了先前的结论，即这些寡糖是膜磷脂极性头部基团的受体，因为磷脂酰甘油的未酯化甘油磷酸是一个sn - 甘油 - 1 - P残基，在自然界中此残基较为罕见。膜衍生寡糖中的甘油磷酸残基在sn - 2或sn - 3位置未被取代，因为它们在温和条件下很容易被高碘酸盐氧化。碱性水解会释放出甘油磷酸，且仅释放出极少量的游离甘油，这与甘油磷酸残基通过6位与葡萄糖单元相连的观点一致，6位不利于形成会消除游离甘油的葡萄糖环磷酸中间体。寡糖A - 1（但不是组分A - 2）含有相当于总磷30%至40%的磷酸乙醇胺残基。磷酸乙醇胺残基与葡萄糖单元的6位相连，这一点通过部分酸水解产物中分离出6 - 磷酸葡萄糖得以证明。
