Figure 1

Structure of Kdo ₂ -lipid A from E. coli K12. Parts joined by the nine enzymes are indicated with shadow and dashed surrounding. The nine-enzyme pathway is illustrated at the bottom. Abbreviations for enzymes and substrates are as follows: LpxA: UDP-N-acetylglucosamine acyltransferase, LpxC: UDP-3-O-(3-hydroxymyristoyl) N-acetylglucosamine deacetylase, LpxD: UDP-3-O-(3-hydroxymyristoyl) glucosamine N-acyltransferase, LpxH: UDP-2,3-diacylglucosamine pyrophosphatase, LpxB: lipid-A-disaccharide synthase, LpxK: lipid A 4'-kinase, WaaA (or KdtA): 3-deoxy-D-manno-octulosonate-lipid A transferase (or Kdo-lipid A transferase), LpxL (or HtrB): Kdo₂-lipid IV_A lauroyl-ACP acyltransferase, LpxM (or MsbB): Kdo₂-lauroyl-lipid IV_A -myristoyl-ACP acyltransferase, ACP: acyl carrier protein, UDP: uridine diphosphate, UDP-GlcNAc: UDP-N-acetylglucosamine, and DS-1-P: tetraacyldisaccharide 1-phosphate. In the pathway, substrates are shown with numbers as follows: 1: UDP-3-O-(3-hydroxytetradecanoyl)-N-acetylglucosamine, 2: UDP-3-O-(3-hydroxytetradecanoyl)-glucosamine, 3: UDP-2,3-bis(3-hydroxytetradecanoyl)-glucosamine, 4: 2,3-bis(3-hydroxytetradecanoyl)-beta-D-glucosaminyl 1-phosphate, 5: tetraacyldisaccharide 1,4'-bis-phosphate (lipid IV_A), 6: Kdo₂-lipid IV_A, and 7: Kdo₂-(lauroyl)-lipid IV_A.