tailieunhanh - Báo cáo khóa học: Modulation of activity of NADH oxidase from Thermus thermophilus through change in flexibility in the enzyme active site induced by Hofmeister series anions

The conformational dynamics of NADH oxidase from Thermus thermophiluswas modulated by the Hofmeister series of anions (H2PO4 – ,SO4 2– ,CH3COO – ,Cl – ,Br – ,I – , ClO4 – ,SCN – ) in the concentration range 0–3M. Both cha-otropic and kosmotropic anions,at high concentration, inhibit the enzyme by different mechanisms. Chaotropic anions increase the apparent Michaelis constant and decre-ase the activation barrier of the reaction. Kosmotropic ani-ons have the opposite effect. | Eur. J. Biochem. 271 4S 7 2004 FEBS 2003 doi Modulation of activity of NADH oxidase from Thermus thermophilus through change in flexibility in the enzyme active site induced by Hofmeister series anions Gabriel Zoldak1 Mathias Sprinzl2 and Erik Sedlak1 1 Department of Biochemistry Faculty of Sciences P. J. Safarik University Kosice Slovakia 2Laboratorium fur Biochemie Universitat Bayreuth Germany The conformational dynamics of NADH oxidase from Thermus thermophilus was modulated by the Hofmeister series of anions H2PO4- SO42- CHI3COO CT Hr I- ClO4 SCN in the concentration range 0-3 M. Both cha-otropic and kosmotropic anions at high concentration inhibit the enzyme by different mechanisms. Chaotropic anions increase the apparent Michaelis constant and decrease the activation barrier of the reaction. Kosmotropic anions have the opposite effect. Anions from the middle of the Hofmeister series do not significantly affect the enzyme activity even at high concentration. We detected no significant changes in ellipticity of the aromatic region in the presence of the anions studied. There is a decreased Stem-Volmer quenching constant for FAD fluorescence quenching in the presence of kosmotropic anions and an increased quenching constant in the presence of chaotropic anions. All of this indicates that active site flexibility is important in the function of the enzyme. The data demonstrate that both the high rigidity of the active site in the presence of kosmotropic anions and its high flexibility in the presence of chaotropic anions have a decelerating effect on enzyme activity. The Hofmeister series of anions proved to be suitable agents for altering enzyme activity through changes in flexibility of the polypeptide chain with potential importance in modulating extremozyme activity at room temperature. Keywords activation conformational dynamics flavoproteins NADH oxidase Thermus thermophilus. The native conformation of an enzyme is produced .