Two pyruvates to valine in four steps. Humans cannot make valine. Most microorganisms, such as E. coli, can
Route: Pyruvate + Pyruvate → (2S)-2-Acetolactate → (2R)-2,3-Dihydroxyisovalerate → α-Ketoisovalerate → Valine
Valine is an essential amino acid for humans, so this pathway is not available to humans. The first enzyme joins two pyruvates and releases CO₂, using thiamine pyrophosphate as a helper. The second enzyme rearranges the carbon skeleton and reduces it with NADPH. The third removes water and leaves a keto acid, α-ketoisovalerate. The last step is a transamination from glutamate, as in the alanine pathway. α-Ketoisovalerate is also the start of the leucine pathway.
Practice this pathway All pathways
| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | Acetolactate synthase | 2.2.1.6 | CO₂ | |
| 2 | Ketol-acid reductoisomerase | 1.1.1.86 | NADPH | NADP⁺ |
| 3 | Dihydroxy-acid dehydratase | 4.2.1.9 | H₂O | |
| 4 | Branched-chain aminotransferase | 2.6.1.42 | Glutamate | α-KG |
Enzyme names and EC numbers are those used on the interactive board. Checked against sources: see the claim table in the repository (tools/pathway_data/checks).