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