Medicine & USMLE

Galactose Metabolism

Biochemical Pathways
  1. Glycolysis
  2. Citric Acid Cycle (TCA Cycle)
  3. Electron Transport Chain (ETC)
  4. Cori Cycle
  5. De Novo Purine Synthesis
  6. De Novo Pyrimidine Synthesis
  7. Purine Salvage
  8. Purine Excretion
  9. Ethanol Metabolism
  10. Pyruvate Metabolism
  11. HMP Shunt (Pentose Phosphate Pathway)
  12. Galactose Metabolism
  13. Sorbitol (Polyol) Pathway
  14. Urea Cycle
  15. Alanine (Cahill) Cycle
  16. Catecholamine Synthesis & Breakdown
  17. Homocysteine Metabolism
  18. Fatty Acid Synthesis (Citrate Shuttle)
  19. Fatty Acid Breakdown (Carnitine Shuttle)
  20. Propionic Acid Pathway
  21. Fructose Metabolism
  22. Regulation by Fructose-2,6-Bisphosphate (F-2,6-BP)
  23. Glycogenesis
  24. Glycogenolysis

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.