Transketolase activity in erythrocytes is used as a functional test for which vitamin deficiency, and what is the basis for this test?

• A Riboflavin; transketolase requires FAD as cofactor
• B Thiamine; transketolase requires thiamine pyrophosphate as cofactor ✓
• C Niacin; transketolase requires NAD+ as cofactor
• D Pyridoxine; transketolase requires PLP as cofactor

Explanation

Transketolase is a key enzyme of the HMP (pentose phosphate) shunt that transfers two-carbon units between sugars. It requires thiamine pyrophosphate (TPP) as its essential cofactor. Erythrocyte transketolase activity, measured as the TPP activation effect (TPPE) — the percentage increase in activity after adding excess TPP in vitro — is the most sensitive and specific laboratory test for subclinical thiamine (vitamin B1) deficiency. A TPPE >15–25% indicates thiamine depletion. This test is more sensitive than serum thiamine levels.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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