Pathway · 2 proteins
Lipopolysaccharide biosynthesis
Proteins of this group that KEGG places on its “Lipopolysaccharide biosynthesis” map for Aquifex aeolicus.
How it works
This map shows how lipid A, the anchor of the outer layer, and the sugars attached to it are built. The two proteins here carry out steps in building lipid A: an LpxI-type enzyme that makes a lipid A precursor, and the kinase that adds the 4′ phosphate.
Grouped by KEGG pathway map. The explanation above is the atlas’s own; the map itself covers more organisms than Aquifex.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| LpxI family protein | — | — | — | 305 | Step named |
| Tetraacyldisaccharide 4'-kinase | 2.7.1.130 | a lipid A disaccharide + ATP = a lipid IVA + ADP + H(+) | — | 315 | Step named |
Also part of this pathway
These proteins are described under another pathway, but also take part here.
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| UDP-3-O-acyl-N-acetylglucosamine deacetylaseHome: Lipid A and outer envelope | 3.5.1.108 | a UDP-3-O-[(3R)-3-hydroxyacyl]-N-acetyl-alpha-D-glucosamine + H2O = a UDP-3-O-[(3R)-3-hydroxyacyl]-alpha-D-glucosamine + acetate | Zn(2+) | 282 | Step named |
| Acyl-[acyl-carrier-protein]--UDP-N-acetylglucosamine O-acyltransferaseHome: Lipid A and outer envelope | 2.3.1.129 | a (3R)-hydroxyacyl-[ACP] + UDP-N-acetyl-alpha-D-glucosamine = a UDP-3-O-[(3R)-3-hydroxyacyl]-N-acetyl-alpha-D-glucosamine + holo-[ACP] | — | 261 | Step named |
| Lipid-A-disaccharide synthaseHome: Lipid A and outer envelope | 2.4.1.182 | a lipid X + a UDP-2-N,3-O-bis[(3R)-3-hydroxyacyl]-alpha-D-glucosamine = a lipid A disaccharide + UDP + H(+) | — | 356 | Step named |
| 3-deoxy-D-manno-octulosonic acid transferaseHome: Lipid A and outer envelope | 2.4.99.12 | lipid IVA (E. coli) + CMP-3-deoxy-beta-D-manno-octulosonate = alpha-Kdo-(2->6)-lipid IVA (E. coli) + CMP + H(+) | — | 353 | Step named |
| ADP-heptose:LPS heptosyltransferaseHome: Not yet placed in a pathway | — | — | — | 317 | Unspecified |
Origins
How could the sugar-rich outer layer of the envelope have formed before these enzymes existed?
None of the books searched discusses a prebiotic route to lipopolysaccharide.
Lipopolysaccharide is built inside the cell and must then be carried across two membranes to the outer surface, so its synthesis is useless without the machinery that moves it.
The wider question for this part of the cell: origins for building and maintaining the membrane.
Sources
- KEGG map aae00540 (enzymes of this organism highlighted)
Other pathways in this group: Glycerolipid assembly · Lipid A and outer envelope · Fatty-acid elongation · Substrate recognition · Terpenoid backbone biosynthesis · Fatty acid biosynthesis · Biosynthesis of various nucleotide sugars · Not yet placed in a pathway