The chemical structures of the capsular polysaccharides from Streptococcus pneumoniae types 32F and 32A

The structures of the capsular polysaccharides from Streptococcus pneumoniae types 32F and 32A have been determined by means of NMR spectroscopy as the principal method. It is concluded that both polysaccharides are composed of tetrasaccharide repeating units with a phosphorylcholine (PCho) group linked to the 3-position of the 4-substituted beta-L-rhamnose (Rha) residue. Both polysaccharides are substituted with one O-acetyl group at the 2-position of the same beta-L-rhamnose residue. In addition, the type-32A polysaccharide is substituted with another O-acetyl group at the 4-position of the 2,3-disubstituted alpha-D-glucose residue, i.e. the branch-point residue. An unusual detail in the structure is that the side chain is composed of a rhamnosyl phosphate. [chemical structure: see text] In the type-32F polysaccharide R=H, and in the type-32A polysaccharide R=Ac. The structure of C-polysaccharide found in our preparations of type-32F and type-32A capsular polysaccharides is in agreement with that published previously for the pneumococcal common antigen C-polysaccharide [Fischer, W., Behr, T., Hartmann, R., Peter-Katalinic, J. & Egge, H. (1993) Eur. J. Biochem. 215, 851-857; Kulakowska, M., Brisson, J.-R., Griffith, D. W., Young, N. M. & Jennings, H. J. (1993) Can. J. Chem. 71, 644-648].