Pathway · 3 proteins
Fatty acid biosynthesis
Proteins of this group that KEGG places on its “Fatty acid biosynthesis” map for Aquifex aeolicus.
How it works
This map shows how fatty acids are built two carbons at a time on the acyl carrier protein, and how they are activated for use. The proteins here load malonyl groups onto the carrier, reduce the growing chain, and attach coenzyme A to fatty acids.
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 |
|---|---|---|---|---|---|
| 3-oxoacyl-[acyl-carrier-protein] reductase FabG | 1.1.1.100 | a (3R)-hydroxyacyl-[ACP] + NADP(+) = a 3-oxoacyl-[ACP] + NADPH + H(+) | — | 248 | Step named |
| Malonyl CoA-acyl carrier protein transacylase | 2.3.1.39 | holo-[ACP] + malonyl-CoA = malonyl-[ACP] + CoA | — | 326 | Step named |
| Long-chain-fatty-acid CoA ligase | — | a long-chain fatty acid + ATP + CoA = a long-chain fatty acyl-CoA + AMP + diphosphate | — | 823 | 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 |
|---|---|---|---|---|---|
| Acetyl-coenzyme A carboxylase carboxyl transferase subunit alphaHome: Lipid and cofactor connections | 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 carboxylaseHome: Lipid and cofactor connections | — | — | — | 154 | Step named |
| Biotin carboxylaseHome: Lipid and cofactor connections | 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 betaHome: Lipid and cofactor connections | 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 |
| 3-hydroxyacyl-[acyl-carrier-protein] dehydratase FabZHome: Fatty-acid elongation | 4.2.1.59 | a (3R)-hydroxyacyl-[ACP] = a (2E)-enoyl-[ACP] + H2O | — | 150 | Step named |
| Beta-ketoacyl-[acyl-carrier-protein] synthase IIIHome: Fatty-acid elongation | 2.3.1.180 | malonyl-[ACP] + acetyl-CoA + H(+) = 3-oxobutanoyl-[ACP] + CO2 + CoA | — | 309 | Step named |
| Enoyl-[acyl-carrier-protein] reductase [NADH] FabIHome: Fatty-acid elongation | 1.3.1.9 | a 2,3-saturated acyl-[ACP] + NAD(+) = a (2E)-enoyl-[ACP] + NADH + H(+) | — | 270 | Step named |
| 3-oxoacyl-[acyl-carrier-protein] synthase 2Home: Fatty-acid elongation | 2.3.1.179 | (9Z)-hexadecenoyl-[ACP] + malonyl-[ACP] + H(+) = 3-oxo-(11Z)-octadecenoyl-[ACP] + holo-[ACP] + CO2 | — | 415 | Step named |
Origins
Could fatty acids long enough to make a membrane have formed before cells?
How it was discovered
- late 1950sSalih Wakil finds that malonyl-CoA is the building unit of fatty acids, after Feodor Lynen had shown the central role of acetyl-CoA.Zubay, Origins of Life on Earth and in the Cosmos, p. 336
The Murchison meteorite contains a series of monocarboxylic acids from formic acid up to the 12-carbon dodecanoic acid, and Deamer counts these among possible membrane-forming compounds.
Deamer also notes that chains shorter than 14 carbons cannot assemble into stable membranes; membrane fatty acids are typically 14 to 18 carbons long. Straight-chain fatty acids have not been convincingly made under simulated prebiotic conditions.
In the cell, eight enzyme-catalysed reactions turn acetyl-CoA into a fatty acid, and the first one spends ATP to supply the energy for the rest.
From the books: Deamer, Assembling Life, pp. 35 and 56; Garrett & Grisham, Biochemistry, p. 665; Zubay, Origins of Life on Earth and in the Cosmos, p. 336.
The wider question for this part of the cell: origins for building and maintaining the membrane.
Sources
- KEGG map aae00061 (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 · Lipopolysaccharide biosynthesis · Biosynthesis of various nucleotide sugars · Not yet placed in a pathway