InterPro domain: IPR007691

This entry represents LpxD, an enzyme for the biosynthesis of lipid A, a component oflipopolysaccharide (LPS) in the outer membrane outer leaflet of most Gram-negative bacteria. Some differences are found between lipid A of different species. This protein represents the third step from UDP-N-acetyl-D-glucosamine [ 1 ]. The group added at this step generally is 14:0(3-OH) (myristate) but may vary; in Aquifex it appears to be 16:0(3-OH) (palmitate) [ 2 ].

Lipid A-like molecules in plants may serve as structural components of the outer membranes of mitochondria and/or chloroplasts, or may be involved in signal transduction or plant defense responses [ 3 , 4 ].

1. The firA gene of Escherichia coli encodes UDP-3-O-(R-3-hydroxymyristoyl)-glucosamine N-acyltransferase. The third step of endotoxin biosynthesis. J. Biol. Chem. 268, 19866-74
2. Characterization of a novel lipid A containing D-galacturonic acid that replaces phosphate residues. The structure of the lipid a of the lipopolysaccharide from the hyperthermophilic bacterium Aquifex pyrophilus. J. Biol. Chem. 275, 11222-8
3. Pathway for lipid A biosynthesis in Arabidopsis thaliana resembling that of Escherichia coli. Proc. Natl. Acad. Sci. U.S.A. 108, 11387-92
4. Innate immunity in Arabidopsis thaliana: lipopolysaccharides activate nitric oxide synthase (NOS) and induce defense genes. Proc. Natl. Acad. Sci. U.S.A. 101, 15811-6