Coenzyme required for transketolase reaction is: (A) Ca2+, (B) Mg2+, (C) H+, (D) PO4-
Answer is B. Transketolase transfers the two-carbon unit comprising carbons 1 and 2 of a ketose onto the aldehyde carbon of an aldose sugar. It, therefore, effects the conversion of a ketose sugar into an aldose with two carbons less and an aldose sugar into a ketose with two carbons more. The reaction requires Mg2+ and thiamin diphosphate (vitamin B1) as the coenzyme. Measurement of erythrocyte transketolase and its activation by thiamin diphosphate provides an index of vitamin B1 nutritional status.Ref: Harper&;s Biochemistry; 30th edition; Chapter 20; The Pentose Phosphate Pathway & Other Pathways of Hexose Metabolism