Collect. Czech. Chem. Commun. 2006, 71, 1588-1610

A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction

Joaquin F. Perez-Benito

Departamento de Quimica Fisica, Facultad de Quimica, Universidad de Barcelona, Marti i Franques, 1, 08028 Barcelona, Spain


The kinetics of the reaction of cytochrome c with H2O2 was studied in aqueous phosphate media near physiological pH (5.7-7.2). The UV-VIS spectra indicated that the heme prosthetic group of the protein suffered an oxidative degradation during the reaction. The experimental rate law was v = kexp [cytochrome c] [H2O2], with kexp = (A + B [H+])/(1 + C [H+]). The apparent activation parameters associated with kexp were Ea = 46 ± 2 kJ mol-1, ∆Ho = 43 ± 2 kJ mol-1 and ∆So = -111 ± 5 J K-1 mol-1. The reaction showed base catalysis and was also catalyzed by both CrO42- and acrylamide. It was inhibited by the oxidants WO42-, MoO42-, VO3- and [Fe(CN)6]3- as well as by the reductants [Fe(CN)6]4- and D-mannitol, whereas Zn2+ and superoxide dismutase had no appreciable effect. The results are consistent with initial reduction of iron from Fe(III) to Fe(II) (supported by inhibition caused by most oxidants), followed by a hydroxyl-radical mediated oxidative degradation of the heme prosthetic group (supported by the inhibition caused by both [Fe(CN)6]4- and D-mannitol).

Keywords: Cytochrome c; Hydrogen peroxide; Hydroxyl radicals; Kinetics; Mechanism; Proteins; Oxidative degradation; UV-VIS spectroscopy.

References: 64 live references.