Acetyl-CoA to CO₂, one turn of the citric acid cycle in the mitochondrial matrix. Succinate dehydrogenase sits in the inner membrane
Route: Oxaloacetate + Acetyl-CoA → Citrate → Isocitrate → α-KG → Suc-CoA → Succinate → Fumarate → Malate → Oxaloacetate
Neutral forms, drawn in the same pose from one step to the next. Oxaloacetate is both the first and the last compound: it takes up the next acetyl-CoA and the cycle turns again. CoA stands for the whole coenzyme A residue. One turn releases two CO₂ and makes three NADH, one FADH₂ and one ATP or GTP (muscle uses an ADP-specific form of succinyl-CoA synthetase, liver a GDP-specific form).
Practice this pathway All pathways
| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | Citrate synthase | 2.3.3.1 | H₂O | CoA-SH |
| 2 | Aconitase | 4.2.1.3 | ||
| 3 | Isocitrate dehydrogenase (NAD) | 1.1.1.41 | NAD⁺ | NADH, CO₂ |
| 4 | α-Ketoglutarate dehydrogenase complex | 1.2.1.105 | NAD⁺, CoA-SH | NADH, CO₂ |
| 5 | Succinyl-CoA synthetase | 6.2.1.5 | ADP, Pᵢ | CoA-SH, ATP |
| 6 | Succinate dehydrogenase | 1.3.5.1 | FAD | FADH₂ |
| 7 | Fumarase | 4.2.1.2 | H₂O | |
| 8 | Malate dehydrogenase | 1.1.1.37 | NAD⁺ | NADH |
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).