PMID:3549716

Anderson, MS and Raetz, CR (1987) Biosynthesis of lipid A precursors in Escherichia coli. A cytoplasmic acyltransferase that converts UDP-N-acetylglucosamine to UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine.J. Biol. Chem. 262:5159-69

Abstract

Preliminary studies from our laboratory have suggested the existence of a novel set of fatty acyltransferases in extracts of Escherichia coli that attach two R-3-hydroxymyristoyl moieties to UDP-GlcNAc (Anderson, M.S., Bulawa, C.E., and Raetz, C.R.H. (1985) J. Biol. Chem. 260, 15536-15541). The resulting "glucosamine-derived" phospholipids appear to be crucial precursors for the biosynthesis of the lipid A component of lipopolysaccharide. We now describe an assay and a 1000-fold purification of the first enzyme in this pathway, which catalyzes the reaction: UDP-GlcNAc + R-3-hydroxymyristoyl-acyl carrier protein----UDP-3-O-(R-3-hydroxymyristoyl)-GlcNAc + acyl carrier protein. The covalent structure of the monoacylated UDP-GlcNAc product was established by fast atom bombardment mass spectrometry and 1H-NMR spectroscopy. The UDP-GlcNAc acyltransferase has a strict requirement for R-3-hydroxymyristoyl-acyl carrier protein, since R-3-hydroxymyristoyl coenzyme A and myristoyl-acyl carrier protein are not substrates. Of various NDP-GlcNAc preparations examined, only the uridine and thymidine derivatives were utilized to a significant extent. When the product of the reaction (UDP-3-O-(R-3-hydroxymyristoyl)-GlcNAc) was isolated and reincubated with crude E. coli extracts, it was rapidly converted to more hydrophobic products in the presence of R-3-hydroxymyristoyl-acyl carrier protein. We propose that the addition of an R-3-hydroxymyristoyl residue to the 3 position of the GlcNAc moiety of UDP-GlcNAc is the first committed step in lipid A biosynthesis and that UDP-GlcNAc is situated at a biosynthetic branchpoint in E. coli leading either to lipid A or to peptidoglycan.

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Annotations

Gene product	Qualifier	GO ID	GO term name	Evidence Code	with/from	Aspect	Notes	Status
LpxA		GO:0008780	acyl-(acyl-carrier-protein)-UDP-N-acetylglucosamine O-acyltransferase activity	IDA: Inferred from Direct Assay		F	Assayed using [-32P]UDP-GlcNAc and R-3-hydroxymyristoyl acyl carrier protein as substrates. Product was separated from reactants by thin layer chromatography and quantified by scintillation counting. Substrates are not commercially available but their preparation is described.	complete
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