This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: vitamins, Subject name: Biochemistry
In Beri-Beri, which enzyme activity is measured? 
Select and explain. 
A. Transketolase, B. Tranaminase, C. Decarboxylase, D. Deaminase
A: Transketolase
Answer: A: Transketolase 
Explanation: Severe thiamine deficiency is associated with: Decreased RBC transketolase activity this is the earliest manifestation seen even before clinical disturbances Thiamin is a cofactor of Transketolase pyruvate, alpha-ketoglutarate and lactate level in blood increases in thiamine deficiency ref: DM Vasudevan 8th ed page 467