Roll No: 37
GLUCONEOGENESIS
Gluconeogenesis: -
Definition:-
➢ The Synthesis of glucose from non -carbohydrate compounds is known as
“Gluconeogenesis”.
➢ The major su bstrate/precursor for gluconeogenesis are lactate, pyruvate, glycogenic
amino acids, propionate and glycol.
Location:-
➢ Gluconeogenesis occurs mainly in the cytosol, although some precursors are produced
in the mitochondria.
➢ It mostly takes place in liver (about 1kg glucose/day) and to some extent in kidney matrix
(about one-tenth of liver capacity)
Reaction of Gluconeogenesis:-
➢ Gluconeogenesis closely resembles the reversed pathway of glycolysis, althou gh it is
not the complete reversal of glycolysis.
➢ Essentially, 3 (out of 10) reaction of glycolysis are irreversible.
➢ The seven reactions are common for both glycolysis and gluconeogenesis.
➢ The Three irreversible steps of glycolysis are catalysed by the enzymes namely
hexokinase, phosphofructokinase and pyruvate kinase.
Conversion of Pyruvate to Phosphoenol pyruvate:-
➢ This takes place in two steps. Pyruvate carboxylase is a biotin -dependent
mitochondrial en zyme that converts pyruvate to oxaloacetate in the presence of ATP
and CO2. This enzyme regulates gluconeogenesis.
➢ Oxaloacetate is synthesized in the mitochondrial matrix. It has to be transported to the
cytosol to be used in gluconeogenesis, where the rest of the pathway occurs. Due to
membrane impermeability, oxaloacetate cannot diffuse out of the mitochondria. It is
converted to malate and then transported to the cytosol. Within the cytosol,
