Metabolic pathway
β-oxidation
Takes a fatty acid apart two carbons at a time. Each turn yields one acetyl-CoA, one FADH2 and one NADH, and leaves a shorter chain that goes back in. With palmitate the spiral turns seven times and produces eight acetyl-CoA.
- In
- Palmitate + 8 Coenzyme A + ATP + 7 FAD + 7 NAD⁺ + 7 Water
- Out
- 8 Acetyl-CoA + AMP + Pyrophosphate + 7 FADH₂ + 7 NADH + 7 Proton
- Location
- Mitochondrial matrix
Fun facts
- Long-chain acyl-CoA synthetaseThe pyrophosphate released is destroyed right away by another enzyme. That second cut is what makes the activation irreversible in practice: removing a product pulls the reaction forward.
- Carnitine palmitoyltransferase · carnitine shuttleMalonyl-CoA, the first molecule of fat synthesis, blocks this gate. That way the cell cannot make and burn fatty acids at the same time: one pathway shuts the other with its own product.
Reactions
| # | Enzyme | ΔG°′ |
|---|---|---|
| 1 | Long-chain acyl-CoA synthetaseEC 6.2.1.3 · irreversiblePalmitate + Coenzyme A + ATP → Palmitoyl-CoA + AMP + Pyrophosphate | — |
| 2 | Carnitine palmitoyltransferase · carnitine shuttleEC 2.3.1.21 · irreversiblePalmitoyl-CoA → Fatty acyl-CoA | — |
| 3×7 | Acyl-CoA dehydrogenaseEC 1.3.8.8 · irreversibleFatty acyl-CoA + FAD → trans-Δ2-Enoyl-CoA + FADH₂ | — |
| 4×7 | Enoyl-CoA hydrataseEC 4.2.1.17trans-Δ2-Enoyl-CoA + Water ⇌ L-3-Hydroxyacyl-CoA | — |
| 5×7 | 3-hydroxyacyl-CoA dehydrogenaseEC 1.1.1.35L-3-Hydroxyacyl-CoA + NAD⁺ ⇌ 3-Ketoacyl-CoA + NADH + Proton | — |
| 6×6 | ThiolaseEC 2.3.1.16 · irreversible3-Ketoacyl-CoA + Coenzyme A → Acetyl-CoA + Fatty acyl-CoA | — |
| 7 | Thiolase · last turnEC 2.3.1.16 · irreversible3-Ketoacyl-CoA + Coenzyme A → 2 Acetyl-CoA | — |
0 of 7 reactions with a documented ΔG.
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The data sheet includes the map. The logo goes at the bottom.
Sources
- Nelson, D. L. & Cox, M. M. (2021). Lehninger. Principios de bioquímica, 8.ª ed., ch. 17