Single Amino Acid Substitution (Gly456Ala) in the Vicinity of the GTP Binding Domain of Human Housekeeping Glutamate Dehydrogenase Markedly Attenuates GTP Inhibition and Abolishes the Enzyme ́s Cooperative Behavior*

Short running title: Human GDH Mutagenesis Affects GTP Inhibition * This work was supported by the Association for Research and Treatment of Neurological Disorders of Crete «Εύ Ζήν» and a training grant (“Maria Manasaki”) by the University of Crete (to I.Z.). ♣To whom correspondence should be addressed: Professor and Chairman, Department of Neurology, University of Crete, School of Health Sciences, Section of Medicine, 71500 Heraklion, Crete, Greece. Tel. +30-810-394647/8; Fax +30-810-394839; e-mail: [email protected]