# 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](/content/view/4329/index.html)), 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](/content/view/3653/index.html)  
    - **α-ketoglutarate dehydrogenase**  
      - Enzyme in the TCA cycle  
    - **Transketolase**  
      - Important in [Hexose Monophosphate (HMP) Shunt](/content/view/4957/index.html)  
      - Erythrocyte (RBC) transketolase activity decreased in deficiency  
    - **Branched-chain ketoacid dehydrogenase**  
      - Thiamine supplementation useful in [Maple Syrup Urine Disease (MSUD)](/content/view/4215/index.html), caused by deficiency of above

Find Thiamine Biochemistry and other [Vitamins](/content/browse#playlist-2700/index.html) among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.