Regulation of carbohydrate metabolism

Overview of the major pathways of glucose metabolism

Regulation of gluconeogenesis and glycolysis:

inactivation of the glycolytic enzymes and activation of the enzymes of gluconeogenesis

1. Pyruvate ↔ PEP

Pyruvate kinase - inactivation by cAMP (glucagon)

Phosphoenolpyruvate carboxykinase -induced by glucagon, epinephrine, and

cortisol

2. Fructose 1,6-P ↔ Fructose 6-P

Phosphofructokinase - activated by fructose 2,6-P

Fructose 1,6-bisphosphatase - inhibited by fructose 2,6-P

3. Glucose 6-P ↔ Glucose

Glucokinase - high Km for glucose, induced by insulin

Glucose 6-phosphatase - induced during fasting

Metabolism of glycogen

Regulation of glycogenolysis in the liver by glucagon:

cAMP → protein kinase A:

1. inactivates glycogen synthase

2. activates glycogen phosphorylase

Regulation of glycogenolysis in muscle: