Wzydependent

Wzy-dependent is a major bacterial polysaccharide biosynthesis pathway most commonly associated with the production of the O-antigen portion of lipopolysaccharide and with certain capsular polysaccharides. The name derives from the Wzy family of polysaccharide polymerases that catalyze the polymerization of repeating unit oligosaccharides into longer chains.

In this pathway, a repeating sugar unit is assembled on the lipid carrier undecaprenyl phosphate (Und-PP) on the cytoplasmic face of the inner membrane by a series of glycosyltransferases encoded in a gene cluster. The completed repeating unit is then translocated across the inner membrane by the Wzx flippase. In the periplasm, the Wzy polymerase links individual repeating units into a growing polysaccharide chain. The length of the polymer is regulated by Wzz, which controls the modal chain length and distribution. Some systems employ multiple Wzz homologs to produce distinct length profiles. Once polymerized, the polymer is exported to the cell surface as part of the lipopolysaccharide or capsule assembly process.

Wzy-dependent systems are widespread among Gram-negative bacteria and contribute substantially to antigenic diversity, virulence, and immune evasion through variation in O-antigen structure. The gene clusters typically contain wzx, wzy, and wzz genes alongside numerous glycosyltransferases that build the repeat units. The pathway is one of several strategies bacteria use to assemble surface polysaccharides; others include ABC transporter-dependent and synthase-dependent mechanisms.

Overall, the Wzy-dependent pathway is a fundamental mechanism by which bacteria generate diverse, highly variable surface polysaccharides that influence interactions with hosts and the environment.