The first sugar of the repeat units is essential for the Wzy polymerase activity and elongation of the O-antigen lipopolysaccharide.

In the Wzx/Wzy-dependent assembled pathway, the assembled O-antigen repeat units are translocated from the cytosolic to the periplasmic face of the inner membrane by a Wzx translocase and then polymerized by the integral membrane protein Wzy to form a glycan chain. We demonstrate that the activity of the Escherichia coli O-antigen polymerase (Wzy) is dependent on the first sugar of the O-antigen repeat unit to produce the O-antigen polymerization and therefore, there is a need for a concerted action with the enzyme transferring the initial HexNAc to undecaprenyl phosphate (UDP-HexNAc: polyprenol-P HexNAc-1-P transferase). Furthermore, in the case of Aeromonas hydrophila Wzy-O34 polymerization activity, the enzyme is permissive with the sugar at the nonreducing end of the O-antigen repeat unit.