<prompt> Coenzyme required for transketolase reaction isCa2Mg2HPO4-  <response>: 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 