Two steps from GABA to succinate, a Krebs cycle intermediate
Route: γ-Aminobutyrate (GABA) → Succinate semialdehyde → Succinate
GABA aminotransferase moves the amino group of GABA to α-ketoglutarate. This gives glutamate and succinate semialdehyde, and the enzyme needs pyridoxal phosphate. Succinate-semialdehyde dehydrogenase then oxidizes the aldehyde group with NAD⁺ and water and gives succinate. Both enzymes are mitochondrial in humans. Succinate enters the Krebs cycle. The two steps give a route from α-ketoglutarate to succinate that bypasses part of the cycle and is called the GABA shunt. In neurons, the glutamate formed in the first step can serve to make GABA again, by glutamate decarboxylase in the cytosol.
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| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | 4-Aminobutyrate aminotransferase (GABA transaminase) | 2.6.1.19 | α-KG | Glutamate |
| 2 | Succinate-semialdehyde dehydrogenase | 1.2.1.24 | NAD⁺, H₂O | NADH |
Build any of these from its atoms.
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).