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Mechanisms of bovine liver glutamate dehydrogenase self-association. I. Kinetic evidence for a random association of polymer chains.
Authors:D Thusius  P Dessen  J M Jallon
Institution:1. Laboratoire d''Enzymologie Physico-chimique et Moléculaire Faculté des Sciences, 91400 Orsay, France;2. Laboratoire d''Enzymologie du Centre National de la Recherche Scientifique 91190 Gif-sur-Yvette, France;3. Centre de Génétique Moléculaire du Centre National de la Recherche Scientifique 91190 Gif-sur-Yvette, France
Abstract:We have undertaken a study of the mechanism of bovine liver glutamate dehydrogenase self-association with scattered light temperature-jump and stopped-flow relaxation techniques. Our results indicate a “random association” mechanism in which association-dissociation reactions occur between all polymerized forms of the oligomer according to
/></figure> where the specific rate-constants <em>k</em><sub><em>a</em></sub> and <em>k</em><sub><em>d</em></sub> are independent of chain length. At 15 °C we find <em>k</em><sub><em>a</em></sub> = 1.5 × 10<sup>6</sup><em>m</em><sup>?1</sup><em>s</em><sup>?1</sup> and <em>k</em><sub><em>d</em></sub> = 5 <em>s</em><sup>?1</sup>. Standard thermodynamic functions and activation parameters have been determined from equilibrium and kinetic experiments at different temperatures. Large entropy effects and heat capacities indicate water participation in the self-aggregation process. We suggest that the rate-determining step in the association of glutamate dehydrogenase molecules is the “melting” of a layer of ordered water structure between two hydrophobic contact sites.</td>
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