Dynamics stimulation of the holotransketolase molecule revealed that the enzyme's conformation in crystal was different from that in solution. It was shown also that dissolved holotransketolase can bind aldose (the acceptor substrate) even in the absence of ketose (the donor substrate). The holotransketolase conformation did not change upon aldose binding unlike in the case of ketose binding/cleavage. Therefore the conformation of a catalytic complex of holotransketolase with an intermediate-i.e., a glycolaldehyde residue formed upon binding and subsequent cleavage of ketose-differed, at least in solution, from the conformation of both the free and aldose-complexed holotransketolase. Some structural peculiarities of the holotransketolase with the intermediate were established by means of molecular dynamics stimulation.