[Modification of glutamate dehydrogenase by pyridoxal-5'-phosphate. Study of the structural organisation of the hexamer and its possible role in the realization of GTP action].
The catalytic and regulator properties of glutamate dehydrogenase by modification of Lys-126 residue by puridoxal-5'-phosphate was studied. The phosphopyridoxyl derivative of the enzyme with blocked NADH-induced binding site of GTP not capable of being polymerized was taken as a model. It was shown that: blocking the epsilon-amino group of Lys-126 residue brings to a simultaneous inactivation of the enzyme and desensibilization of its residual activity to GTP action; the modification of Lys-126 residue and resulting inactivation of the enzyme and desensibilization to GTP action were non-cooperative processes, with equal values of pseudofirst order rate constants; modification of Lys-126 residue of any of hexamer's protomer results in the desensibilization to GTP action on one of the contacting, catalytically active protomers. The experimental dependence of the inhibition degree of the enzyme by GTP upon the average number of modified residues of Lys-126 is explained by the model of the hexamer of glutamate dehydrogenase with identical interlocation of any of the protomers in relation to the one in contact.
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D005969:Glutamate Dehydrogenase / Q000037:antagonists & inhibitors*; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008958:Models, Molecular; D011487:Protein Conformation
D006160:Guanosine Triphosphate; D005969:Glutamate Dehydrogenase
Modifikatsiia glutamatdegidrogenazy piridoksal'-5'-fosfatom. Izuchenie strukturnoĭ organizatsii geksamera i ego vozmozhnoĭ roli v realizatsii deĭstviia GTP.