Some structural features of Pneumococcus Type XXII capsular polysaccharide

Abstract

The capsular polysaccharide of Pneumococcus Type XXII (S XXII) was freed from impurities and found to contain phosphate (0·4%), erthyritol (3%), and D-glucose, D-galactose, L-arabinose, L-rhamnose, and D-glucuronic acid in the molar ratio 7·0 : 2·5 : 2·0 : 4·8 : 2·8. Mild acidic hydrolysis gave an aldobiouronic acid characterised as 3-O-α-D-glucuronopyranosyl-D-glucose. Graded hydrolysis of S XXII yielded, besides the aldobiouronic acid, three disaccharides, viz. 4-O-β-D-glucopyranosyl-D-glucose, 5-O-β-D-galactopyranosyl-L-arabinose, and 3-O-β-D-galactopyranosyl-L-arabinose, and a small amount of a trisaccharide containing galactose, arabinose, and rhamnose. The identification of these oligosaccharides revealed some of the structural details of the polysaccharide.