Romanowska E

S19.7 Studies on glycine as a component of bacterial lipopolysaccharides

The aminoacyl analysis of endotoxic lipopolysaccharides (LPS) isolated from several bacteria revealed the essential amounts of glycine, among the inherent LPS components. This prompts for the detailed investigation in view of the search for common epitopes suitable for construction of antimicrobial vaccine with broad specificity. The glycine, possibly unifying the LPS structures, might create the common epitope. Significant amounts of glycine was detected in lipopolysaccharides isolated from over 30 strains of Shigella, Escherichia coli, Salmonella, Hafnia and Citrobacter. When the O-specific polysaccharide, lipid A and core fractions of Shigella flexneri and sonnei LPSs were subjected to aminoacyl analysis, glycine as a single aminoacid was found only in core oligosaccharide. The quantity of the aminoacid was not stoichiometric in core oligosaccharides. Molar ratio of glycine ranged from 0.2 to 0.6 per 3 heptoses. Using the HPLC the oligosaccharide enriched in glycine was isolated. Mild acid treatment (0.05 M HC1, 15 min, 100°C) released free glycine. The aminoacid could be also partially cleaved (in 50°70) by pronase digestion. Growing E. coli C600 or Sh. sonnei phase II in the presence of radioactive ~4C-Gly, the labelling of their lipopolysaccharide cores was achieved. The experiments indicate that glycine is covalently bound component of core oligosaccharide in bacterial lipopolysaccharides.