Structural studies of the capsular polysaccharide of Acinetobacter calcoaceticus BD4

Abstract

Compositional analysis of the intact and carboxyl-reduced capsular polysaccharide of Acinetobacter calcoaceticus BD4 (PS-4) showed it to consist of l-rhamnose, d-glucose, d-glucuronic and d-mannose in molar ratios of 4:1:1:1. ¹³C-nuclear magnetic resonance spectroscopy, methylation analysis, oligosaccharide analysis and base-catalyzed β-elimination were used to elucidate the primary structure. Oligosaccharides were obtained by enzymatic depolymerization with a specific bacteriophage-induced depolymerase and by partial acid hydrolysis. From the results it is concluded that PS-4 consists of repeating units of the heptasaccharide The bacteriophage-induced depolymerase was found to be an endo-β-d-glucosidase that hydrolyzed the bond β-d-Glc-(1→3)-l-Rha to generate a heptasaccharide in 40% yield.