Kinetic studies of iron deposition in horse spleen ferritin using H2O2 and O2 as oxidants

Biophysical Chemistry
Thomas J LoweryG D Watt

Abstract

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 minera...Continue Reading

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Citations

Aug 10, 2006·Journal of Biological Inorganic Chemistry : JBIC : a Publication of the Society of Biological Inorganic Chemistry·Bo ZhangGerald D Watt
Nov 18, 2005·Analytical Biochemistry·Guanghua Zhao, N Dennis Chasteen
Jun 22, 2017·Biochemistry·Matthew MehlenbacherFadi Bou-Abdallah
Apr 13, 2010·Biochimica Et Biophysica Acta·Fadi Bou-Abdallah

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