Abstract
The thermostability of 3-isopropylmlate dehydrogenase (IPMDH) is reviewed based on its three dimensional structure. The three dimensional structures of an extreme thermophilic, mesophilic and chimeric enzymes are found to be similar with one another, although they have the same function and different thermostabilities. They are composed of two identical monomers, each of which is comprised of two domains. The open and closed conformation, in each subunit, has been determined from the three dimensional structures determined by the X-ray diffraction method. From a comparison of the primary and three-dimensional structures, and site-directed mutagenesis, residues have been identified that contribute to the thermal stability of the IPMDH.