Gluconeogenesis Steps

Gluconeogenesis Steps

Gluconeogenesis is a metabolic pathway that generates glucose from non-carbohydrate sources. The process involves 11 steps, which can be divided into two phases: the pyruvate-to-phosphoenolpyruvate phase and the phosphoenolpyruvate-to-glucose phase.

Phase 1: Pyruvate to Phosphoenolpyruvate (Steps 1-3)

1. Pyruvate carboxylase: Pyruvate is converted to oxaloacetate in the mitochondria, requiring ATP and CO2.
   • Reaction: Pyruvate + CO2 + ATP → Oxaloacetate + ADP + Pi
2. Phosphoenolpyruvate carboxykinase: Oxaloacetate is converted to phosphoenolpyruvate (PEP) in the cytosol.
   • Reaction: Oxaloacetate + GTP → PEP + CO2 + GDP
3. Mitochondrial transport: PEP is transported from the cytosol to the mitochondria.

Phase 2: Phosphoenolpyruvate to Glucose (Steps 4-11)

4. Enolase: PEP is converted to 2-phosphoglycerate (2-PG) in the cytosol.
   • Reaction: PEP → 2-PG
5. Phosphoglycerate mutase: 2-PG is converted to 3-phosphoglycerate (3-PG).
   • Reaction: 2-PG → 3-PG
6. Phosphoglycerate kinase: 3-PG is converted to glyceraldehyde 3-phosphate (G3P) and ATP.
   • Reaction: 3-PG + ATP → G3P + ADP + Pi
7. Triosephosphate isomerase: G3P is converted to glyceraldehyde (GAL).
   • Reaction: G3P → GAL
8. Aldolase: GAL is converted to fructose 1,6-bisphosphate (F1,6BP).
   • Reaction: GAL → F1,6BP
9. Fructose 1,6-bisphosphatase: F1,6BP is converted to fructose 6-phosphate (F6P).
   • Reaction: F1,6BP → F6P
10. Glucose 6-phosphatase: F6P is converted to glucose 6-phosphate (G6P).
    • Reaction: F6P → G6P
11. Glucose 6-phosphatase: G6P is converted to glucose, which is released into the bloodstream.
    • Reaction: G6P → Glucose + Pi