TIM catalyses the interconversion of a triosephosphate aldehyde into a triosephosphate ketone. This is a simple chemical reaction in which only protons are transferred, The crystallographic studies of TIM from chicken, yeast and trypanosome complexed with substrate and substrate analogues are discussed. The substrate binds in a deep pocket. On substrate binding, large conformational changes are induced in three loops. As a result of these conformational changes in the liganded Structure, the active site pocket is sealed off from bulk solvent and the sidechain of the catalytic glutamate becomes optimally positioned for catalysis.
