Pathway · 5 proteins
Lipid and cofactor connections
Acyl precursors and carrier molecules connect biosynthetic branches.
How it works
- Acetyl-CoA carboxylase appears here in its dissociated bacterial form: a biotin carboxylase subunit, a biotin carboxyl carrier protein and two carboxyltransferase subunits.
- The carboxylase commits acetyl-CoA to malonyl-CoA, which an acyl carrier protein holds while the fatty-acid enzymes in the lipid system extend it.
- The same acetyl-CoA pool also supplies coenzyme A and NAD chemistry described in the cofactor system, so this module is a distribution point rather than a single reaction sequence.
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 |
|---|---|---|---|---|---|
| Acetyl-coenzyme A carboxylase carboxyl transferase subunit alpha | 2.1.3.15 | N(6)-carboxybiotinyl-L-lysyl-[protein] + acetyl-CoA = N(6)-biotinyl-L-lysyl-[protein] + malonyl-CoA | — | 323 | Step named |
| Biotin carboxyl carrier protein of acetyl-CoA carboxylase | — | — | — | 154 | Step named |
| Biotin carboxylase | — | — | — | 477 | Step named |
| Biotin carboxylase | 6.3.4.14 | N(6)-biotinyl-L-lysyl-[protein] + hydrogencarbonate + ATP = N(6)-carboxybiotinyl-L-lysyl-[protein] + ADP + phosphate + H(+) | — | 444 | Step named |
| Acetyl-coenzyme A carboxylase carboxyl transferase subunit beta | 2.1.3.15 | N(6)-carboxybiotinyl-L-lysyl-[protein] + acetyl-CoA = N(6)-biotinyl-L-lysyl-[protein] + malonyl-CoA | Zn(2+) | 276 | 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 |
|---|---|---|---|---|---|
| Pyruvate carboxylase n-terminal domainHome: Not yet placed in a pathway | — | — | — | 472 | System only |
Origins
How could lipids and the cofactors that build them have appeared together?
Single-chain fatty acids and isoprenoids could be produced in some prebiotic scenarios. Glycerol-linked and more complex lipids are increasingly difficult, and the review authors assume they appeared later through biosynthesis.
Fatty acids in the cell are built on the acyl carrier protein, which carries a pantetheine arm attached to it. Lipid building therefore needs coenzyme A chemistry first, and coenzyme A needs its own pathway.
From the books: Ruiz-Mirazo et al., Prebiotic Systems Chemistry, PDF p. 29; Ribas de Pouplana (ed.), The Genetic Code and the Origin of Life, p. 67.
The wider question for this part of the cell: origins for manufacturing cofactors and vitamins.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Heme and quinones · Biotin and lipoate · NAD and flavins · Thiamine and pyridoxal · Folate and pterin chemistry · Coenzyme A · Aspartate-family branches · Amino-acid connections · Folate-linked carbon transfer · Serine, glycine and sulfur · Folate biosynthesis · Oxidative phosphorylation · Thiamine metabolism · Pantothenate and CoA biosynthesis · Glycine, serine and threonine metabolism · Riboflavin metabolism · Nicotinate and nicotinamide metabolism · Biotin metabolism · Cysteine and methionine metabolism · Porphyrin metabolism · Pyruvate metabolism · Not yet placed in a pathway