Erythrocytes transketolase enzyme activity is an indicator of thiamine status.

• Thiamine is converted to its active form, thiamine pyrophosphate (TPP).
• Transketolase is a TPP-dependent enzyme of the hexose monophosphate (HMP) shunt pathway.
• The HMP shunt is the major source of NADPH in erythrocytes.
• NADPH is required to maintain glutathione in the reduced form, which protects red blood cells from oxidative damage.
• In thiamine deficiency, TPP formation is reduced, leading to decreased transketolase activity in erythrocytes.
• Therefore, erythrocyte transketolase activity is a sensitive indicator of thiamine status.