Glucogenesis

• Irreversible steps of glycolysis

  • Hexokinase
  • Phosphofructokinase
  • Pyruvate kinase
• Gluconeogenesis


  1. Mainly occurs in cytosol

  2. Some precursors are produced in mitochondria

  3. Takes place in liver and kidney

  4. Synthesis of glucose or glycogen from non carbohydrates like pyruvate, lactate glucogenic amino acids, glycerol and propionic acid

  5. Involves steps of TCA cycle and reversal of glycolysis
• Alternate enzymes specific to gluconeogenesis

  • Pyruvate carboxylase
  • Phosphoenolpyruvate carboxykinase (PEPCK)
  • Fructose 1,6-Bis phosphatase
  • Glucose 6-phosphatase
• The pathway of gluconeogenesis meets the needs of the body for glucose
• Speaker: 'Prof S Nayak'
• Continuous supply of glucose is 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, Pro  KG  oxaloacetate  Glucose
  • Val, Isoleucine, Met  succinyl CoA
  • Propionyl CoA  succinyl CoA  oxaloacetate
• Cori’s Cycle

  1. Glucose/Glycogen converted to lactate in the muscle and this lactate is converted back to glucose in the liver

  2. 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 stimulate gluconeogenesis
  • Insulin inhibits gluconeogenesis
  • Glucogenic amino acids have a stimulating effect on key gluconeogenic enzymes
  • Acetyl CoA promotes gluconeogenesis
  • Starvation leads to excessive lipolysis in adipose tissues, acetyl CoA accumulates in the liver, and acetyl CoA stimulates gluconeogenic enzymes
• Reference: 'Essentials of Biochemistry, Dr S Nayak'