Gluconeogenesis

Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors e.g.:

• lactate
• glycerol
• pyruvate
• certain amino acids

Gluconeogenesis occurs predominantly in the liver; it can also occur in the renal cortex. The pathway contains many enzymes which are active in glycolysis. However, gluconeogenesis is not simply a reversal of glycolysis as the enzymes pyruvate kinase, 6-phosphofructokinase and hexokinase have their equilibrium in favour of the forward reaction. New enzymes need to be recruited to the cause.

Gluconeogenesis has a key role in the maintenance of blood glucose levels during certain stresses e.g. prolonged starvation. After 12-24 hours of fasting, glycogen reserves are depleted and the body reverts to gluconeogenesis to supply glucose for tissues with an obligatory dependence e.g. the brain.

Reference

1. Han HS, Kang G, Kim JS, Choi BH, Koo SH. Regulation of glucose metabolism from a liver-centric perspective. Exp Mol Med. 2016 Mar 11;48(3):e218.