A chronic alcoholic has recently had trouble with their ability to balance, becomes easily confused, and displays nystagmus. An assay of which of the following enzymes can determine a biochemical reason for these symptoms?

The patient has the symptoms of beriberi, which is caused by a thiamin deficiency. Of the enzymes listed, transketolase would be less active because it requires thiamin pyrophosphate as a cofactor. The other enzymes listed do not require cofactors except for the three dehydrogenases, which require either NAD+orNADP+, depending on the enzyme.