Mechanism of O-specific polysaccharide biosynthesis in Salmonella serogroups C2 and C3

Cell envelope and soluble glycosyl transferase preparations from Salmonella newport (serogroup C2) and Salmonella kentucky (serogroup C3) were found to catalyze 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 uridine diphosphate galactose onto the acceptor is followed by two consecutive mannosyl transfers from guanosine diphosphate mannose and rhamnosyl transfer thymidine diphosphate rhamnose. Uridine diphosphate 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 polymerised 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.