Biosynthesis, transport, and modification of lipid A

Biochem Cell Biol. 2004 Feb;82(1):71-86. doi: 10.1139/o03-070.


Lipopolysaccharide (LPS) is the major surface molecule of Gram-negative bacteria and consists of three distinct structural domains: O-antigen, core, and lipid A. The lipid A (endotoxin) domain of LPS is a unique, glucosamine-based phospholipid that serves as the hydrophobic anchor of LPS and is the bioactive component of the molecule that is associated with Gram-negative septic shock. The structural genes encoding the enzymes required for the biosynthesis of Escherchia coli lipid A have been identified and characterized. Lipid A is often viewed as a constitutively synthesized structural molecule. However, determination of the exact chemical structures of lipid A from diverse Gram-negative bacteria shows that the molecule can be further modified in response to environmental stimuli. These modifications have been implicated in virulence of pathogenic Gram-negative bacteria and represent one of the molecular mechanisms of microbial surface remodeling used by bacteria to help evade the innate immune response. The intent of this review is to discuss the enzymatic machinery involved in the biosynthesis of lipid A, transport of the molecule, and finally, those enzymes involved in the modification of its structure in response to environmental stimuli.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Biological Transport / physiology
  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • Escherichia coli / genetics
  • Gram-Negative Bacteria / chemistry
  • Gram-Negative Bacteria / genetics
  • Gram-Negative Bacteria / metabolism*
  • Lipid A / biosynthesis
  • Lipid A / chemistry
  • Lipid A / metabolism*
  • Lipopolysaccharides / chemistry
  • Lipopolysaccharides / metabolism
  • Models, Biological
  • Molecular Sequence Data


  • Lipid A
  • Lipopolysaccharides