Pathway · 5 proteins
Aspartate-family branches
Routes connect aspartate chemistry to several amino acids.
How it works
- Oxaloacetate connects central carbon metabolism to aspartate formation.
- Aspartate-family routes branch through activated and reduced intermediates. Lysine synthesis proceeds through diaminopimelate-related chemistry in the selected bacterial example; threonine production uses homoserine-related steps.
- Methionine, lysine and threonine are different endpoint branches, not consecutive products of one linear pathway. Homologous enzymes can have different substrate ranges, so annotations need pathway-specific confirmation.
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 |
|---|---|---|---|---|---|
| Aspartokinase | 2.7.2.4 | L-aspartate + ATP = 4-phospho-L-aspartate + ADP | — | 415 | Step named |
| Homoserine kinase | 2.7.1.39 | L-homoserine + ATP = O-phospho-L-homoserine + ADP + H(+) | — | 297 | Step named |
| Homoserine dehydrogenase | 1.1.1.3 | L-homoserine + NADP(+) = L-aspartate 4-semialdehyde + NADPH + H(+) | — | 435 | Step named |
| Diaminopimelate epimerase | 5.1.1.7 | (2S,6S)-2,6-diaminopimelate = meso-2,6-diaminopimelate | — | 279 | Step named |
| Aspartate-semialdehyde dehydrogenase | 1.2.1.11 | L-aspartate 4-semialdehyde + phosphate + NADP(+) = 4-phospho-L-aspartate + NADPH + H(+) | — | 340 | 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 |
|---|---|---|---|---|---|
| Diaminopimelate decarboxylaseHome: Aspartate-family branches | 4.1.1.20 | meso-2,6-diaminopimelate + H(+) = L-lysine + CO2 | — | 420 | Step named |
| LL-diaminopimelate aminotransferaseHome: Aspartate-family branches | 2.6.1.83 | (2S,6S)-2,6-diaminopimelate + 2-oxoglutarate = (S)-2,3,4,5-tetrahydrodipicolinate + L-glutamate + H2O + H(+) | — | 387 | Step named |
| Threonine synthaseHome: Aspartate-family branches | 4.2.3.1 | O-phospho-L-homoserine + H2O = L-threonine + phosphate | — | 409 | Step named |
| UDP-N-acetylmuramoyl-L-alanyl-D-glutamate--2,6-diaminopimelate ligaseHome: Peptidoglycan precursors | 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 |
Origins
Could aspartate and the amino acids made from it have been available before these branches existed?
Aspartic acid can be produced under simulated prebiotic conditions and is counted among the amino acids that could have been available first. Zubay discusses how carbohydrates could have supplied carbon skeletons for many amino acids on the early Earth.
From aspartate the cell makes lysine, methionine, threonine and isoleucine. In E. coli the first step is carried out by three versions of the same enzyme, each switched off by a different end product, so that one product cannot shut down the supply of the others.
From the books: Rogers, Integrated Molecular Evolution, p. 91; Zubay, Origins of Life on Earth and in the Cosmos, p. 283; Nelson & Cox, Lehninger Principles of Biochemistry, p. 872.
The wider question for this part of the cell: origins for making the twenty amino acids.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Aromatic amino acids · Branched-chain amino acids · Nitrogen assimilation · RNA maturation · Folate-linked carbon transfer · Arginine biosynthesis · Cysteine and methionine metabolism · Histidine metabolism · Lysine biosynthesis · Arginine and proline metabolism · Phenylalanine, tyrosine and tryptophan biosynthesis · Not yet placed in a pathway