A novel cytokine-inducing glycolipid isolated from the lipoteichoic acid fraction of Enterococcus hirae ATCC 9790: A fundamental structure of the hydrophilic part

Previously, we showed that quantitatively minor several glycolipids only le ss than 5% of the lipoteichoic acid (LTA) fraction from Enterococcus hirae ATCC 9790 possessed cytokine-inducing activity, whereas the major component (over 90%) did not [Suda et al. (1995) FEMS Immun Med Microbiol 12:97-112] . The major inactive component was shown to have the chemical structure as was proposed for the LTA by Fischer [Hashimoto et al. (1997) J Biochem 121: 779-86], suggesting that so-called LTA is not a cytokine-inducing component in the Gram-positive bacteria. In the present paper, the structure of the hydrophilic part of one of the cytokine-inducing glycolipid tentatively nam ed GL4 is elucidated. GL4 was first subjected to hydrolysis with aqueous HF to give a polysaccharide and a mixture of low molecular weight products. T he polysaccharide was composed mainly of highly branching mannan as conclud ed from NMR and MS analyses of its acetolysis products. The low molecular w eight products consisted of phosphate and glycerol, suggesting the presence of a poly(glycerophosphate) structure in the original GL4. From these obse rvations, the hydrophilic part of GL4 was shown to consist of mannose-rich polysaccharide and poly(glycerophosphate), the latter being bound to the fo rmer by a phosphodiester linkage.