. "Cytosolic transketolase catalyzes the reversible reaction of D-glyceraldehyde 3-phosphate and sedoheptulose 7-phosphate to form D-xylulose 5-phosphate and D-ribose 5-phosphate. The active transketolase enzyme is a homodimer with one molecule of thiamine pyrophosphate and magnesium bound to each monomer (Wang et al. 1997)."^^ . . .