Structural studies of capsular polysaccharide of type XII diplococcus pneumoniae

Abstract

The capsular polysaccharide of Diplococcus pneumoniae Type XII contains residues of -glucose and -galactose in a molar ratio of 2:1. The methylated polysaccharide yielded upon hydrolysis 2,3,4,6-tetra- and 3,4,6-tri-O-methyl--glucose and 2,3,4,6-tetra-O-methyl--galactose as the only neutral methyl sugars. Periodate oxidation of the polysaccharide resulted in destruction of all neutral sugars and immunochemical activity against rabbit antisera. Periodate oxidation of the methyl O-methylglycosides obtained after hydrolysis of the methylated polysaccharide indicated that at least 30% of the -fucosamine residues are substituted at C-4 in the polysaccharide. It is concluded that the polysaccharide consists of a hexosamine backbone that is substituted by -galactosyl and kojibiosyl side-chains. The proposed terminal -galactosyl residues apparently are sterically hindered from interacting with several -galactose-binding proteins.