A Bifunctional Enzyme in a Single Gene Catalyzes the Incorporation of GlcN into the Aeromonas Core Lipopolysaccharide |
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| Authors: | Natalia Jimenez Silvia Vilches Anna Lacasta Miguel Regu?? Susana Merino and Juan M Tom??s |
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| Institution: | From the ‡Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona, Diagonal 645, 08071 Barcelona and ;the §Departamento de Microbiología y Parasitología Sanitarias, Facultad de Farmacia, Universidad de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain |
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| Abstract: | The core lipopolysaccharide (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 GlcN 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 GlcNAc from UDP-GlcNAc to the outer core LPS. Independent expression of the carbohydrate esterase domain leads to the deacetylation of the GlcNAc 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 GlcN in their outer core LPS the two reactions are performed by two different enzymes. |
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