Pathway · 9 proteins
Peptidoglycan precursors
Mur and D-Ala enzymes generate cell-wall building blocks.
How it works
- UDP-N-acetylglucosamine is converted by MurA, a 1-carboxyvinyltransferase, and MurB, a dehydrogenase, to UDP-N-acetylmuramate. This is the committed step of cell-wall precursor synthesis.
- MurC, MurD and MurE ligases add L-alanine, D-glutamate and diaminopimelate in sequence. Alanine racemase supplies D-alanine and a D-alanine--D-alanine ligase makes the dipeptide.
- The dipeptide is attached by MurF and the completed unit is transferred to a lipid carrier by MraY, a phospho-N-acetylmuramoyl-pentapeptide transferase. That transfer is the step that moves the precursor to the membrane for polymerisation.
Grouped by the atlas’s curated pathway map. The table order is not a proven reaction order.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| Phospho-N-acetylmuramoyl-pentapeptide-transferase | 2.7.8.13 | UDP-N-acetyl-alpha-D-muramoyl-L-alanyl-gamma-D-glutamyl-meso-2,6-diaminopimeloyl-D-alanyl-D-alanine + di-trans,octa-cis-undecaprenyl phosphate = di-trans,octa-cis-undecaprenyl diphospho-N-acetyl-alpha-D-muramoyl-L-alanyl-D-glutamyl-meso-2,6-diaminopimeloyl-D-alanyl-D-alanine + UMP | Mg(2+), Mn(2+) | 359 | Step named |
| UDP-N-acetylglucosamine 1-carboxyvinyltransferase | 2.5.1.7 | phosphoenolpyruvate + UDP-N-acetyl-alpha-D-glucosamine = UDP-N-acetyl-3-O-(1-carboxyvinyl)-alpha-D-glucosamine + phosphate | — | 425 | Step named |
| UDP-N-acetylmuramate--L-alanine ligase | 6.3.2.8 | UDP-N-acetyl-alpha-D-muramate + L-alanine + ATP = UDP-N-acetyl-alpha-D-muramoyl-L-alanine + ADP + phosphate + H(+) | — | 454 | Step named |
| UDP-N-acetylmuramoyl-L-alanyl-D-glutamate--2,6-diaminopimelate ligase | 6.3.2.13 | UDP-N-acetyl-alpha-D-muramoyl-L-alanyl-D-glutamate + meso-2,6-diaminopimelate + ATP = UDP-N-acetyl-alpha-D-muramoyl-L-alanyl-gamma-D-glutamyl-meso-2,6-diaminopimelate + ADP + phosphate + H(+) | Mg(2+) | 482 | Step named |
| UDP-N-acetylmuramoylalanine--D-glutamate ligase | 6.3.2.9 | UDP-N-acetyl-alpha-D-muramoyl-L-alanine + D-glutamate + ATP = UDP-N-acetyl-alpha-D-muramoyl-L-alanyl-D-glutamate + ADP + phosphate + H(+) | — | 415 | Step named |
| UDP-N-acetylenolpyruvoylglucosamine reductase | 1.3.1.98 | UDP-N-acetyl-alpha-D-muramate + NADP(+) = UDP-N-acetyl-3-O-(1-carboxyvinyl)-alpha-D-glucosamine + NADPH + H(+) | — | 213 | Step named |
| UDP-N-acetylenolpyruvoylglucosamine reductase | 1.3.1.98 | UDP-N-acetyl-alpha-D-muramate + NADP(+) = UDP-N-acetyl-3-O-(1-carboxyvinyl)-alpha-D-glucosamine + NADPH + H(+) | — | 297 | Step named |
| D-alanine--D-alanine ligase | 6.3.2.4 | 2 D-alanine + ATP = D-alanyl-D-alanine + ADP + phosphate + H(+) | Mg(2+), Mn(2+) | 291 | Step named |
| UDP-N-acetylmuramoyl-tripeptide--D-alanyl-D-alanine ligase | 6.3.2.10 | D-alanyl-D-alanine + UDP-N-acetyl-alpha-D-muramoyl-L-alanyl-gamma-D-glutamyl-meso-2,6-diaminopimelate + ATP = UDP-N-acetyl-alpha-D-muramoyl-L-alanyl-gamma-D-glutamyl-meso-2,6-diaminopimeloyl-D-alanyl-D-alanine + ADP + phosphate + H(+) | — | 445 | 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 |
|---|---|---|---|---|---|
| Alanine racemaseHome: Not yet placed in a pathway | 5.1.1.1 | L-alanine = D-alanine | — | 338 | Step named |
Origins
Could the building blocks of the cell wall have been made before these enzymes existed?
The books searched discuss peptidoglycan only in present-day bacteria; archaea have cell walls without it. None describes a prebiotic route to its sugar-peptide units.
Each wall unit is a sugar pair carrying a short peptide that includes D-amino acids, assembled step by step inside the cell. Nine proteins of the minimal set serve this assembly, and the finished unit must then be carried across the membrane on a lipid carrier.
From the books: Brooker, Biology, p. 563.
The wider question for this part of the cell: origins for dividing into two cells.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Wall synthesis and remodeling · Division scaffold · Envelope assembly and division · Division-associated membrane parts · Peptidoglycan biosynthesis · Not yet placed in a pathway