Metabolic pathway
Lipogenesis
Assembles sixteen-carbon fatty acids from acetyl-CoA when there is fuel to spare. It is not β-oxidation in reverse: it happens in another compartment, with other enzymes and with NADPH instead of NADH.
- In
- 8 Citrate + 15 ATP + Water + 14 NADPH + 14 Proton
- Out
- Palmitate + 8 Oxaloacetate + 15 ADP + 15 Inorganic phosphate + 14 NADP+
- Location
- Cytosol
Fun facts
- ATP-citrate lyaseCitrate only leaves the mitochondrion when there is plenty of it, that is, when the Krebs cycle is saturated. The same molecule that signals there is energy to spare is the one that carries the carbon to store it.
- Acetyl-CoA carboxylaseThat added carbon is lost again in the next step. It is not built into the fat: it serves to activate the molecule, like setting a lever and removing it once it has done its pushing.
- Fatty acid synthaseThe reducing power comes from NADPH, not NADH. Much of it is made by the pentose phosphate pathway, which is why that pathway runs at the same time as this one.
Reactions
| # | Enzyme | ΔG°′ |
|---|---|---|
| 1×8 | ATP-citrate lyaseEC 2.3.3.8 · irreversibleCitrate + Coenzyme A + ATP → Acetyl-CoA + Oxaloacetate + ADP + Inorganic phosphate | — |
| 2×7 | Acetyl-CoA carboxylaseEC 6.4.1.2 · irreversibleAcetyl-CoA + Carbon dioxide + ATP + Water → Malonyl-CoA + ADP + Inorganic phosphate | — |
| 3 | Fatty acid synthaseEC 2.3.1.85 · irreversibleAcetyl-CoA + 7 Malonyl-CoA + 14 NADPH + 14 Proton → Palmitate + 7 Carbon dioxide + 8 Coenzyme A + 6 Water + 14 NADP+ | — |
0 of 3 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. 21