Transketolase functions to transfer 2 carbon groups from substrates of the PPP, thus rearranging the carbon atoms that enter this pathway. Like other enzymes that transfer 2 carbon groups, transketolase requires thiamine pyrophosphate (TPP) as a co-factor in the transfer reaction.
Transaldolase transfers 3 carbon groups and thus is also involved in a rearrangement of the carbon skeletons of the substrates of the PPP. The transaldolase reaction involves Schiff base formation between the substrate and a lysine residue in the enzyme.