Structure of an acidic polysaccharide from a marine bacterium Pseudoalteromonas distincta KMM 638 containing 5-acetamido-3,5,7,9-tetradeoxy-7-formamido-L-glycero-L-manno-nonulosonic acid

An acidic polysaccharide was obtained from the lipopolysaccharide of Psuedoalteromonas distincta strain KMM 638, isolated from a marine sponge, and found to contain D-GlcA, D-GalNAc, 2-acetamido-2,6-dideoxy-D-glucose (D-QuiNAc) and two unusual acidic amino sugars: 2-acetamido-2-deoxy-D-galacturonic acid (D-GalNAcA) and 5-acetamido-3, 5,7,9-tetradeoxy-7-formamido-L-glycero-L-manno-nonulosonic acid (Pse5Ac7Fo, a derivative of pseudaminic acid). Oligosaccharides were derived from the polysaccharide by partial acid hydrolysis and mild alkaline degradation and characterised by electrospray ionisation (ESI) MS and H-1 and C-13 NMR spectroscopy. Based on these data and NMR spectroscopic studies of the initial and O-deacetylated polysaccharides, including quaternary carbon detection, 2D COSY, TOCSY, ROESY, H-detected H-1,C-13 HMQC and HMBC experiments, the following structure of the branched pentasaccharide repeating unit was established: [GRAPHICS] where the degree of O-acetylation of D-GalpNAcA at position 3 is similar to 60%. (C) 2001 Elsevier Science Ltd. All rights reserved.