A Bifunctional Enzyme in a Single Gene Catalyzes the Incorporation of GIcN into the Aeromonas Core Lipopolysaccharide.

The core Iipopolysaccharide (LPS) of Aeromonas hydrophila AH-3 and Aeromonas salmonicida A450 is characterized by the presence of the pentasaccharide α-D-GlcN-(1→7)-L-α-D-Hep-(1→2)-L-α-D-Hep-(1→3)-L-α-D-Hep-(1→5)-α-Kdo. Previously it has been suggested that the WahA protein is involved in the incorporation of GIcN residue to outer core LPS. The WahA protein contains two domains: a glycosyltransferase and a carbohydrate esterase. In this work we demonstrate that the independent expression of the WahA glycosyltransferase domain catalyzes the incorporation of GIcNAc from UDP-GIcNAc to the outer core LPS. Independent expression of the carbohydrate esterase domain leads to the deacetylation of the GIcNAc residue to GlcN. Thus, the WahA is the first described bifunctional glycosyltransferase enzyme involved in the biosynthesis of core LPS. By contrast in Enterobacteriaceae containing GIcN in their outer core LPS the two reactions are performed by two different enzymes. [ABSTRACT FROM AUTHOR]