Enzyme-like kinetics of ferryloxy myoglobin formation in films on electrodes in microemulsions.
Covalently linked films of the ferric heme protein myoglobin and poly-L-lysine on pyrolytic graphite electrodes reacted with tert-butylhydroperoxide (tBuOOH) to form ferryloxy protein species according to Michaelis-Menten enzyme kinetics. Rotating disk voltammetry data obtained in microemulsions, micellar solution, and buffers revealed a strong influence of water phase acidity on kinetic parameters. Microemulsion and surfactant type had a much smaller influence on reaction kinetics, possibly because the reaction takes place entirely in a water environment surrounding Mb in the films in all fluids. A large apparent Michaelis kcat in microemulsions with neutral water phases was offset by much weaker binding as shown by larger protein-substrate dissociation constants (Km). Acidic SDS microemulsions and pH 2 buffer provided the most efficient reaction conditions as judged by the ratio kcat/Km. Apparent kinetic constants are most likely governed by acidity-controlled protein conformations and their binding with tBuOOH in the intermediate protein-substrate complex.
Guto
Peterson M
PM
Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA.
Rusling
James F
JF
D004563:Electrochemistry; D004566:Electrodes; D004655:Emulsions; D006863:Hydrogen-Ion Concentration; D008786:Metmyoglobin / Q000737:chemistry*; D010084:Oxidation-Reduction; D020122:tert-Butylhydroperoxide / Q000737:chemistry
D004655:Emulsions; C028048:ferrylmyoglobin; D008786:Metmyoglobin; D020122:tert-Butylhydroperoxide