title: Kinetic cooperativity change after H2O2 modification of (Na,K)-ATPase.
abstract: The kinetics of hydrolysis of ATP and p-nitrophenylphosphate and the action of the allosteric effectors, Na+ and K+, upon the hydrolysis of these substrates were used to study the H2O2-modified, uncoupled (Na,K)-ATPase isolated from cultured bovine lenses ( Garner , W. H., Garner , M. H., and Spector , A. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 2044-2048). Pure bovine renal (Na,K)-ATPase was modified by H2O2 in 150 mM KCl and 20 mM MgCl2 to yield an enzyme with kinetic properties similar to the enzyme isolated from the H2O2-treated, cultured bovine lens. H2O2 modification changes the interaction of the ATP hydrolysis site from negative to positive kinetic cooperativity. H2O2 modification dramatically alters Na+ stimulation of ATP hydrolysis and Na+ inhibition of p-nitrophenylphosphate hydrolysis while having little effect upon K+ control of the hydrolysis of these two substrates.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006868:Hydrolysis; D007679:Kidney Medulla / Q000201:enzymology; D007700:Kinetics; D007908:Lens, Crystalline / Q000201:enzymology; D008433:Mathematics; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D009596:Nitrophenols; D009943:Organophosphorus Compounds; C008644:nitrophenylphosphate; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D000254:Sodium-Potassium-Exchanging ATPase