Structural analysis of the carbohydrate backbone of Vibrio parahaemolyticus O2 lipopolysaccharides

A structural investigation has been carried out on the carbohydrate backbone of Vibrio parahaemolyticus 02 lipopolysaccharides (LPS) isolated by dephosphorylation, O-deacylation and N-deacylation. The carbohydrate backbone is a short-chain saccharide consisting of nine monosaccharide units i.e., 1 mol each Of D-galactose (Gal), D-glucose (Glc), D-glucuronic acid (G1cA), L-glycero-D-manno-heptose (D,D-Hep), D-glycero-D-manno-heptose (D,D-Hep), 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo), 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic acid (Non1A), and 2 mol of 2-amino-2-deoxy-D-glucose (D-glucosamine, G1cN). Based on the data obtained by NMR spectroscopy, fast-atom bombardment mass spectrometry (FABMS) and methylation analysis, a structure was elucidated for, the carbohydrate backbone of 02 LPS. In the native 02 LPS, the 2-ammo-2-deoxy-D-glucitol (G1cN-ol) at the reducing end of the nonasaccharide is present as G1cN. The lipid A backbone is a beta-D-G1cN-(1 --> 6)-D-G1cN disaccharide as is the case for many Gram-negative bacterial LPS. The lipid A proximal Kdo is substituted by the distal part of the carbohydrate chain at position-5. In the native O2 LPS, D-galacturonic acid, which is liberated from LPS by mild acid treatment or by dephosphorylation in hydrofluoric acid, is present although its binding position is unknown at present.