The occurrence of glycine in bacterial lipopolysaccharides

The aminoacyl analysis of endotoxic lipopolysaccharides (LPS) isolated from several bacteria revealed essential amounts of glycine, among the inherent LPS components. Significant amounts of the glycine was detected in lipopolysaccharides isolated from over 30 strains of Escherichia, Salmonella, Hafnia, Citrobacter and Shigella species. Glycine as a single amino acid was found only in a core part of LPS. Molar ratio of glycine in core oligosaccharide fraction ranged from 0.2 to 0.6 per 3 heptoses. The oligosaccharide enriched in glycine was isolated using the HPLC. The amino acid appeared to be terminally located in a core oligosaccharide. The labelling of the lipopolysaccharide cores was achieved when the bacteria were cultivated in the presence of radioactive [14C]glycine. The labelled core oligosaccharide released the radioactivity during treatment with mild alkali or acid (0.1 M NaOH or HCl, 100 degrees C, 4 h). The radioactivity in SDS-polyacrylamide gel electrophoresis migrated exclusively with LPS. The results indicate that amino acid is an integral constituent of core oligosaccharide in lipopolysaccharide.