title: Suicide-peroxide inactivation of horseradish peroxidase in the presence of sodium n-dodecyl sulphate: a study of the enzyme deactivation kinetics.
abstract: In the presence of the anionic surfactant sodium n-dodecyl sulphate (SDS), horseradish peroxidase (HRP) undergoes a deactivation process. Suicide inactivation of horseradish peroxidase by hydrogen peroxide(3 mM) was monitored by the absorbance change in product formation in the catalytic reaction cycle. The progress curve of the catalytic reaction cycle was obtained at 27degrees C and phosphate buffer 2.5 mM (pH = 7.0). The corresponding kinetic parameters i.e., intact enzyme activity (alpha i); the apparent rate constant of suicide inactivation by peroxide (ki); and the apparent rate constants of enzyme deactivation by surfactant (kd) were evaluated from the obtained kinetic equations. The experimental data are accounted for by the equations used in this investigation. Addition of SDS to the reaction mixture intensified the inactivation process. The deactivation ability of denaturant could be resolved from the observed inactivation effect of the suicide substrate by applying the proposed model. The results indicate that the deactivation and the inactivation processes are independent of each other.
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: K
authors.initials: K
authors.lastname: Nazari
authors.forename: A
authors.initials: A
authors.lastname: Mahmoudi
authors.forename: M
authors.initials: M
authors.lastname: Shahrooz
authors.forename: R
authors.initials: R
authors.lastname: Khodafarin
authors.forename: A A
authors.initials: AA
authors.lastname: Moosavi-Movahedi
mesh_terms: D002384:Catalysis; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004795:Enzyme Stability; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007700:Kinetics; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D012967:Sodium Dodecyl Sulfate; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase