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Thermoinactivation and reactivation of firefly luciferase Natalia N. Ugarova*; EI Dementieva; IA Lundovskikh Chemistry Department, Lomonosov Moscow State University, Moscow, 119899, Russia      *(unn@enzyme.chem.msu.ru) Thermal inactivation and monomer-dimer interactions of the recombinant Luciola mingrelica firefly luciferase were studied. Ultracentrifugation and analytical gel filtration showed the existence of monomers and dimers for the active luciferase and of trimers for partially inactivated enzyme. The activity - concentration dependencies were typical of oligomeric enzymes indicating the existence of catalytically active monomers and dimers. At 8-22 C monomers in dimers are twice as active as free monomers. The proposed kinetic scheme for thermoinactivation involves (1) reversible dissociation of active dimers into active monomers; (2) reversible inactivation of monomers; (3) irreversible inactivation of monomers and their aggregation. Dimers were shown to be significantly more stable than monomers. At elevated temperatures (30-42 C), monomers inactivate so quickly that step (2) becomes kinetically indistinguishable. Reversibly thermoinactivated luciferase was shown to be able to restore spontaneously its catalytical activity after keeping a sample at decreased temperature. The reactivation involves association of reversibly inactivated monomers into active dimers. [Talk: ugarova.natali.49481]

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