FIG. 1.
The proposed reactions catalyzed by LpxEHP (Hp0021) and EptAHP (Hp0022) of H. pylori. H. pylori synthesizes a minor lipid A species that is bis-phosphorylated and hexa-acylated, resembling E. coli Kdo2-lipid A (37, 58). Modification of the 1 position of H. pylori Kdo2-lipid A is a two-step enzymatic process that involves the removal of the 1-phosphate group by LpxEHP, followed by the addition of a pEtN unit directly to the glucosamine disaccharide backbone by EptAHP (56). Further modifications to the H. pylori lipid A structure are catalyzed by a Kdo (3-deoxy-d-manno-octulosonic acid) hydrolase (51), a 4′-phosphatase (A. X. Tran and M. S. Trent, unpublished data), and a 3′-O-deacylase (C. M. Stead and M. S. Trent, unpublished data), resulting in the major lipid A species produced by the organism (58).