Metabolic pathway
Glycolysis
Splits a hexose into two three-carbon molecules and keeps part of the energy released as ATP and NADH. It works with and without oxygen.
- In
- Glucose + 2 NAD⁺ + 2 ADP + 2 Inorganic phosphate
- Out
- 2 Pyruvate + 2 NADH + 2 Proton + 2 ATP + 2 Water
- Location
- Cytosol
Fun facts
- Hexokinase IIn the liver, glucokinase, or hexokinase IV, acts instead of this isoenzyme. Its Km is about 10 mM, a hundred times higher, so it only phosphorylates glucose when its blood concentration is high, after a meal.
- Phosphofructokinase-1The fructose-2,6-bisphosphate that activates it is not an intermediate of the pathway: it is not part of the sequence. It is a signaling molecule made by PFK-2 in response to insulin, and its only job is to speed up PFK-1.
- Triose phosphate isomeraseIt is a catalytically perfect enzyme: its speed is limited not by its chemistry but by the diffusion of the substrate to the active site. It cannot go any faster.
- Pyruvate kinaseIt is activated by fructose-1,6-bisphosphate, which is made seven steps earlier. It is feed-forward activation: what comes in at the top warns the exit enzyme that work is on the way.
Reactions
| # | Enzyme | ΔG°′ |
|---|---|---|
| 1 | Hexokinase IEC 2.7.1.1 · irreversibleGlucose + ATP → Glucose 6-phosphate + ADP | −16.7kJ/molexergonic |
| 2 | Phosphoglucose isomeraseEC 5.3.1.9Glucose 6-phosphate ⇌ Fructose 6-phosphate | 1.7kJ/molendergonic |
| 3 | Phosphofructokinase-1EC 2.7.1.11 · irreversibleFructose 6-phosphate + ATP → Fructose 1,6-bisphosphate + ADP | −14.2kJ/molexergonic |
| 4 | AldolaseEC 4.1.2.13Fructose 1,6-bisphosphate ⇌ Dihydroxyacetone phosphate + Glyceraldehyde 3-phosphate | 23.8kJ/molendergonic |
| 5 | Triose phosphate isomeraseEC 5.3.1.1Dihydroxyacetone phosphate ⇌ Glyceraldehyde 3-phosphate | 7.5kJ/molendergonic |
| 6×2 | Glyceraldehyde-3-phosphate dehydrogenaseEC 1.2.1.12Glyceraldehyde 3-phosphate + NAD⁺ + Inorganic phosphate ⇌ 1,3-Bisphosphoglycerate + NADH + Proton | 6.3kJ/molendergonic |
| 7×2 | Phosphoglycerate kinaseEC 2.7.2.31,3-Bisphosphoglycerate + ADP ⇌ 3-Phosphoglycerate + ATP | −18.8kJ/molexergonic |
| 8×2 | Phosphoglycerate mutaseEC 5.4.2.113-Phosphoglycerate ⇌ 2-Phosphoglycerate | 4.4kJ/molendergonic |
| 9×2 | EnolaseEC 4.2.1.112-Phosphoglycerate ⇌ Phosphoenolpyruvate + Water | 1.8kJ/molendergonic |
| 10×2 | Pyruvate kinaseEC 2.7.1.40 · irreversiblePhosphoenolpyruvate + ADP → Pyruvate + ATP | −31.4kJ/molexergonic |
10 of 10 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. 14
- Berg, J. M., Tymoczko, J. L., Gatto, G. J. & Stryer, L. (2019). Bioquímica, 9.ª ed., ch. 16