Gluconeogenesis

Irreversible reactions

Gluconeogenesis

• Glucose --> glucose 6-P
  * forward: hexokinase/glucokinase
  * reverse: glucose 6-phosphatase
• Fructose 6-P --> F 1,6-P
  * forward: phosphofructokinase
  * reverse: fructose 1,6-bisphosphatase
• Phosphoenolpyruvate --> pyruvate
  * forward: pyruvate kinase
  * reverse: see below

Pyruvate back to phosphoenolpyruvate

In mitochondria, pyruvate --> oxaloacetate --> malate.

Malate then diffuse into cytosol
--> oxaloacetate

Oxaloacetate (4C) --> phosphoenolpyruvate (3C)
* By phosphoenolpyruvate carboxykinase
* Consumed 1 x GTP

In diabetes mellitus

Increased gluconeogenesis is due to increased activity of

1. Pyruvate carboxylase
   * Converts Pyruvate to oxaloacetate (bypassing acetyl-CoA)
2. Phosphoenolpyruvate carboxykinase
   * Converts Oxaloacetate to phosphoenolpyruvate
3. Fructose 1,6-Bisphosphatase
   * Converts Fructose 1,6-bisphosphate to fructose 6-phosphate
4. Glucose 6-phosphatase
   * Converts glucose 6-phosphate to glucose