A cycle that plays an important role in maintaining blood glucose levels within the normal range (80-120 mg/dL, 4-6 mmol/L). The cycle uses alanine released by the muscle and deaminated by the liver to produce glucose via gluconeogenesis. This glucose is transported to the muscle where it is oxidized to pyruvate that in turn is converted back to alanine. The cycle is an important defense against hypoglycemia during starvation.
Alanine cycle is a series of reactions in which alanine obtained in the muscle from pyruvate through a transamination (pyruvate accepts an amino group from a different amino acid) reaction enters the bloodstream and is taken up by the liver for conversion to glucose by gluconeogenesis. Glucose can be secreted from the liver and then taken up by the muscle where it again produces pyruvate through glycolysis, which is now available once again for transamination to alanine.