USMLE

Galactose Metabolism

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Biochemical Pathways
  1. Glycolysis
  2. Cori Cycle
  3. De Novo Purine Synthesis
  4. De Novo Pyrimidine Synthesis
  5. Purine Salvage
  6. Purine Excretion
  7. Ethanol Metabolism
  8. Pyruvate Metabolism
  9. HMP Shunt (Pentose Phosphate Pathway)
  10. Galactose Metabolism
  11. Sorbitol (Polyol) Pathway
  12. Urea Cycle
  13. Alanine (Cahill) Cycle
  14. Catecholamine Synthesis & Breakdown
  15. Homocysteine Metabolism
  16. Fatty Acid Synthesis (Citrate Shuttle)
  17. Fatty Acid Breakdown (Carnitine Shuttle)
  18. Propionic Acid Pathway

Galactose metabolism is a series of reactions used by the body to process galactose. There are two major pathways which you should remember for test day.

In the first pathway, galactose is converted to galactitol, in a reaction catalyzed by aldose reductase.

In the second pathway, galactose is first converted into galactose-1-phosphate by the enzyme, galactokinase. Next, Galactose-1-phosphate is converted to glucose-1-phosphate, in a reaction catalyzed by a UDP transferase enzyme. In order to keep this reaction running, 4-epimerase is needed to regenerate certain intermediates. Finally, glucose-1-phosphate can enter into the normal glucose metabolism pathways, such as glycolysis and glycogenesis.

Deficiencies in galactokinase can cause Galactokinase Deficiency. Deficiencies in UDP transferase or epimerase can cause Galactosemia.