Vitamin B1 (Thiamine) Biochemistry

Summary

Thiamine (Vitamin B1) is a water-soluble vitamin and an important constituent of TPP (thiamine pyrophosphate), a cofactor found in several important dehydrogenase reactions. Specifically, TPP is an important cofactor for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Besides dehydrogenase reactions, TPP also serves an important role as a cofactor for transketolase.

Key Points

• Vitamin B1 (Thiamine)
  • Active form is thiamine pyrophosphate (TPP), a cofactor for several dehydrogenases and other enzymes:
    • Pyruvate dehydrogenase
      • Links glycolysis to TCA cycle (see Pyruvate Metabolism), enabling cells to metabolize glucose to produce energy
      • Deficiency leads to necrosis of some glucose-dependent tissues (esp. mamillary body in brain), such as seen in Thiamine Deficiency
    • α-ketoglutarate dehydrogenase
      • Enzyme in the TCA cycle
    • Transketolase
      • Important in Hexose Monophosphate (HMP) Shunt
      • Erythrocyte (RBC) transketolase activity decreased in deficiency
    • Branched-chain ketoacid dehydrogenase
      • Thiamine supplementation useful in Maple Syrup Urine Disease (MSUD), caused by deficiency of above

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