Kinetic studies of iron deposition in horse spleen ferritin using H2O2 and O2 as oxidants
| Autor: | Jared Bunker, Gerald D. Watt, Bo Zhang, Robert C. Costen, Thomas J. Lowery |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Iron
Inorganic chemistry Kinetics Biophysics chemistry.chemical_element Biochemistry Oxygen Chemical kinetics Absorbance chemistry.chemical_compound Reaction rate constant Animals Horses Hydrogen peroxide biology Organic Chemistry Hydrogen Peroxide Catalase Oxidants Ferritin chemistry Apoferritins Ferritins biology.protein Spleen |
| Zdroj: | Biophysical Chemistry. 111:173-181 |
| ISSN: | 0301-4622 |
| Popis: | The reaction of horse spleen ferritin (HoSF) with Fe2+ at pH 6.5 and 7.5 using O2, H2O2 and 1:1 a mixture of both showed that the iron deposition reaction using H2O2 is approximately 20- to 50-fold faster than the reaction with O2 alone. When H2O2 was added during the iron deposition reaction initiated with O2 as oxidant, Fe2+ was preferentially oxidized by H2O2, consistent with the above kinetic measurements. Both the O2 and H2O2 reactions were well defined from 15 to 40 degrees C from which activation parameters were determined. The iron deposition reaction was also studied using O2 as oxidant in the presence and absence of catalase using both stopped-flow and pumped-flow measurements. The presence of catalase decreased the rate of iron deposition by approximately 1.5-fold, and gave slightly smaller absorbance changes than in its absence. From the rate constants for the O2 (0.044 s(-1)) and H2O2 (0.67 s(-1)) iron-deposition reactions at pH 7.5, simulations of steady-state H2O2 concentrations were computed to be 0.45 microM. This low value and reported Fe2+/O2 values of 2.0-2.5 are consistent with H2O2 rapidly reacting by an alternate but unidentified pathway involving a system component such as the protein shell or the mineral core as previously postulated [Biochemistry 22 (1983) 876; Biochemistry 40 (2001) 10832]. |
| Databáze: | OpenAIRE |
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