title: Sod and catalase inactivation by singlet oxygen and peroxyl radicals.
abstract: Both superoxide dismutase and catalase are readily deactivated by singlet oxygen and by the radicals produced in the pyrolysis of 2,2'-azo-bis-(2-amidinpropano) under aerobic conditions. The rate constant for the loss of enzymatic activity induced by singlet oxygen are 3.9 x 10(7) and 2.5 x 10(7) M-1 sec-1 for SOD and catalase, respectively. The similarity between these values implies that in systems where SOD and catalase are exposed to similar singlet oxygen concentrations, it can be expected a parallel inactivation of both enzymes. The inactivation of both enzymes by the radicals produced by 2,2'-azo-bis-(2-amidinopropane) pyrolysis under aerobic conditions follows a first-order kinetics at low enzyme concentrations and a zero-order kinetics at higher concentrations. Although at low enzymatic concentrations the rate of inactivation of both enzymes is similar, this results from a compensation of effects because there are wide differences in the reactivity of both enzymes towards peroxyalkyl radicals. Catalase is considerably more reactive, but a large number of protein/radical reactive interactions are needed to inactivate one enzyme. On the other hand, the reactivity of SOD is smaller, but the average enzyme activity decreases by nearly 20% in each SOD/radical reactive interaction.
authors.affiliation: Departamento Ciencias Químicas, Universidad de Santiago de Chile.
authors.forename: J A
authors.initials: JA
authors.lastname: Escobar
authors.forename: M A
authors.initials: MA
authors.lastname: Rubio
authors.forename: E A
authors.initials: EA
authors.lastname: Lissi
mesh_terms: D000818:Animals; D002374:Catalase / Q000037:antagonists & inhibitors*; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004912:Erythrocytes / Q000201:enzymology; D005609:Free Radicals; D007700:Kinetics; D008027:Light; D008099:Liver / Q000201:enzymology; D010100:Oxygen / Q000494:pharmacology*; D010545:Peroxides / Q000494:pharmacology*; D010777:Photochemistry; D012395:Rose Bengal; D026082:Singlet Oxygen; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D005609:Free Radicals; D010545:Peroxides; D026082:Singlet Oxygen; D012395:Rose Bengal; C049375:perhydroxyl radical; D002374:Catalase; D013482:Superoxide Dismutase; D010100:Oxygen