Metabolic pathway
Calvin-Benson cycle
Fixes three molecules of carbon dioxide and turns them into one three-carbon sugar, spending the ATP and NADPH from the light reactions. Most of the cycle is not about fixing carbon, but about rebuilding the molecule that captures it.
- In
- 3 Carbon dioxide + 9 ATP + 6 NADPH + 6 Proton + 5 Water
- Out
- Glyceraldehyde 3-phosphate + 9 ADP + 6 NADP+ + 8 Inorganic phosphate
- Location
- Chloroplast stroma
Fun facts
- RuBisCOIt is the most abundant protein in the biosphere, and also one of the slowest: it fixes only a few molecules per second. Plants make up for it by making huge amounts of it.
Reactions
| # | Enzyme | ΔG°′ |
|---|---|---|
| 1×3 | RuBisCOEC 4.1.1.39 · irreversibleRibulose 1,5-bisphosphate + Carbon dioxide + Water → 2 3-Phosphoglycerate | — |
| 2×6 | Phosphoglycerate kinaseEC 2.7.2.33-Phosphoglycerate + ATP ⇌ 1,3-Bisphosphoglycerate + ADP | — |
| 3×6 | Glyceraldehyde-3-phosphate dehydrogenase (NADP+)EC 1.2.1.131,3-Bisphosphoglycerate + NADPH + Proton ⇌ Glyceraldehyde 3-phosphate + NADP+ + Inorganic phosphate | — |
| 4×2 | Triose phosphate isomeraseEC 5.3.1.1Glyceraldehyde 3-phosphate ⇌ Dihydroxyacetone phosphate | — |
| 5 | AldolaseEC 4.1.2.13Dihydroxyacetone phosphate + Glyceraldehyde 3-phosphate ⇌ Fructose 1,6-bisphosphate | — |
| 6 | Fructose-1,6-bisphosphataseEC 3.1.3.11 · irreversibleFructose 1,6-bisphosphate + Water → Fructose 6-phosphate + Inorganic phosphate | — |
| 7 | TransketolaseEC 2.2.1.1Fructose 6-phosphate + Glyceraldehyde 3-phosphate ⇌ Erythrose 4-phosphate + Xylulose 5-phosphate | — |
| 8 | AldolaseEC 4.1.2.13Erythrose 4-phosphate + Dihydroxyacetone phosphate ⇌ Sedoheptulose 1,7-bisphosphate | — |
| 9 | Sedoheptulose-1,7-bisphosphataseEC 3.1.3.37 · irreversibleSedoheptulose 1,7-bisphosphate + Water → Sedoheptulose 7-phosphate + Inorganic phosphate | — |
| 10 | TransketolaseEC 2.2.1.1Sedoheptulose 7-phosphate + Glyceraldehyde 3-phosphate ⇌ Ribose 5-phosphate + Xylulose 5-phosphate | — |
| 11 | Ribose-5-phosphate isomeraseEC 5.3.1.6Ribose 5-phosphate ⇌ Ribulose 5-phosphate | — |
| 12×2 | Ribulose-5-phosphate 3-epimeraseEC 5.1.3.1Xylulose 5-phosphate ⇌ Ribulose 5-phosphate | — |
| 13×3 | PhosphoribulokinaseEC 2.7.1.19 · irreversibleRibulose 5-phosphate + ATP → Ribulose 1,5-bisphosphate + ADP | — |
0 of 13 reactions with a documented ΔG.
Use Shift to select several
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. 20