Modification of the lipid A domain of lipopolysaccharide (LPS) has been reported to contribute to the virulence and pathogenesis of various Gram-negative bacteria. The Kdo (3-deoxy-D- manno-octulosonic acid)—lipid A domain of Helicobacter pylori LPS shows several differences to that of Escherichia coli. It has fewer acyl chains, a reduced number of phosphate groups, much lower immunobiological activity, and only a single Kdo sugar is attached to the disaccharide backbone. However, H. pylori synthesizes a minor lipid A species resembling that of E. coli, which is both bis-phosphorylated and hexa-acylated suggesting that the major species results from the action of specific modifying enzymes. This work describes two enzymes, a lipid A phosphatase and a phosphoethanolamine transferase, involved in the periplasmic modification of the 1-position of H. pylori lipid A. Furthermore, we report a novel Kdo trimming enzyme that requires prior removal of the 1-phosphate group for enzymatic activity. Discovery of the enzymatic machinery involved in the remodeling of H. pylori LPS will help unravel the importance of these modifications in H. pylori pathogenesis.
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