Transcript Document
Gluconeogenesis
Mainly occurs in cytosol
Some precursors are produced in mitochondria
Takes place in liver and kidney
Synthesis of glucose or glycogen from non
carbohydrates like pyruvate, lactate glucogenic
amino acids, glycerol and propionic acid
Pathway involves steps of TCA cycle and reversal of
glycolysis
The irreversible steps of glycolysis are catalysed by
Hexokinase
Phosphofructokinase and
Pyruvate kinase
These three stages bypassed by alternate enzyme
specific to gluconeogenesis
They are called as key enzymes of gluconeogenesis
1. Pyruvate carboxylase
2. Phosphoenolpyruvate carboxykinase (PEPCK)
3. Fructose 1,6- Bis phosphatase
4. Glucose 6-phosphatase
The pathway meet the needs of the body for
glucose
Continuos supply of glucose required as a source
of energy for the CNS, Brain, RBC and skeletal
muscle during starvation
Substrates for Gluconeogenesis
Gly, Ala, Ser, Thr, Cys, Trp pyruvate oxaloacetate
Phe, Tyr, fumarate
Asp, Asn
Arg, His,Glu, gln, proKGoxaloacetateGlucose
Val, isoleucine, Met succinyl CoA
Propionyl CoA succinyl CoA oxaloacetate
Cori’s Cycle
Glucose/Glycogen converted to lactate in
the muscle and this lactate is converted
back to glucose in liver
During active muscle contraction glycogen
breaks down to generate glucose
Regulation of gluconeogenesis
The glucagon and the availability of substrates mainly
regulate gluconeogenesis
Glucagon & glucocorticoid gluconeogenesis.
Insulin inhibit gluconeogenesis
Glucogenic amino acids have stimulating effect on key
gluconeogenic enzymes
* Acetyl CoA promotes gluconeogenesis
Starvationexcessive lipolysis in adipose
tissues acetyl CoA accumulates in the liver, acetyl CoA stimulate
gluconeogenic enzymes.