Mechanism of O‐Specific Polysaccharide Biosynthesis in Salmonella Serogroups C2 and C3

Abstract

Cell envelope and soluble glycosyl transferase preparations from S. newport (serogroup C2) and S. kentucky (serogroup C3) catalyzed the formation of polyprenyl pyrophosphate tetrasaccharides corresponding to the structure of the repeating unit of the main chain of O-specific polysaccharides. Plant polyprenyl phosphate may serve as an exogenous sugar acceptor. Galactose residue is an initiator of a chain growth: transfer of galactosyl phosphate from UDP-galactose onto the acceptor is followed by 2 consecutive mannosyl transfers from GDP-mannose and rhamnosyl transfer from TDP-rhamnose. UDP-glucose and polyprenyl phosphate are converted by the enzyme preparations into polyprenyl monophosphate glucose which may transfer a glucosyl residue onto the polyprenyl pyrophosphate oligosaccharides. The resulting pentasaccharide derivatives may be polymerized by enzymes present in cell envelope preparations. The significance of these results for the understanding of the mechanism of O-specific polysaccharide biosynthesis is discussed.