Glutamate dehydrogenase from hyperthermophilic Bacteria and Archaea: determinants of thermostability and catalysis at extremely high temperatures

Insight in the molecular mechanisms determining the extreme intrinsic therm ostability of enzymes isolated from hyperthermophilic Archaea and Bacteria, is increasing rapidly as more comparative studies on their amino acid sequ ences, biochemical characteristics and three-dimensional structures are rep orted. In order to test the hypotheses arising from these data, protein eng ineering strategies have been applied to mesophilic and thermostable glutam ate dehydrogenases (GDH) from different prokaryotic sources, followed by bi ochemical and structural characterization of the engineered enzymes. This r eview aims to provide an overview of (i) the state of the art on biochemica l and structural characterization of thermostable GDHs, (ii) the constructi on and properties of hybrid GDHs obtained by domain swapping between GDHs f rom the mesophilic bacterium Clostridium difficile and the hyperthermophili c archaeon Pyrococcus furiosus, and (iii) the elucidation of the role of la rge ion-pair networks in conferring stability to GDHs fi-om hyperthermophil es by the introduction of ion-pair networks into GDH from Thermotoga mariti ma. (C) 1999 Elsevier Science B.V. All rights reserved.