Transketolase activity is seen with which vitamin

Transketolase activity is seen in Vit B1. In thiamine deficiency, blood thiamine is reduced, but pyruvate, alpha-ketoglutarate and lactate are increased. Erythrocyte transketolase activity is reduced; this is the earliest manifestation seen even before clinical disturbances. Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 392