Factors controlling the substrate specificity of peroxidases: kinetics and thermodynamics of the reaction of horseradish peroxidase compound I with phenols and indole-3-acetic acids.
The rates of oxidation of reducing substrates by heme peroxidases have previously been thought to be controlled only by their ease of oxidation. In the present study, we have compared the kinetics and thermodynamics of the oxidation of indole-3-acetic acid and derivatives and of phenols by horseradish peroxidase. Different dependencies of the reaction rates on the thermodynamic driving force reveal substrate specificity controlled by the enzyme-substrate complexes dissociation constants (Michaelis-Menten constants) and by the reorganization energies of electron-transfer within those complexes.
Candeias
L P
LP
Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, U.K. candeias@graylab.ac.uk
Folkes
L K
LK
Wardman
P
P
D002384:Catalysis; D004579:Electron Transport; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D010636:Phenols / Q000378:metabolism*; D013379:Substrate Specificity; D013816:Thermodynamics
D007210:Indoleacetic Acids; D010636:Phenols; C098326:oxyferryl porphyrin pi cation radical; C030737:indoleacetic acid; D006735:Horseradish Peroxidase