A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction

[img]PDF - Authorized users only
Language: English
216Kb
Title:A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction
Creators:
Perez-Benito, Joaquin F.
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 71, 11-12, pp. 1588-1610
Uncontrolled Keywords:Kinetics, Mechanism, Cytochrome <i>c</i>, Hydroxyl radicals, Proteins, Oxidative degradation, UV-VIS spectroscopy, Hydrogen peroxide

Abstract

The kinetics of the reaction of cytochrome <i>c</i> with H<sub>2</sub>O<sub>2</sub> 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 <i>v</i> = <i>k</i><sub>exp</sub> [cytochrome <i>c</i>] [H<sub>2</sub>O<sub>2</sub>], with <i>k</i><sub>exp</sub> = (<i>A</i> + <i>B</i> [H<sup>+</sup>])/(1 + <i>C</i> [H<sup>+</sup>]). The apparent activation parameters associated with <i>k</i><sub>exp</sub> were <i>E</i><sub>a</sub> = 46 ± 2 kJ mol<sup>-1</sup>, ∆<i>H</i><sup>o</sup><sub>≠</sub> = 43&nbsp;± 2 kJ mol<sup>-1</sup> and ∆<i>S</i><sup>o</sup><sub>≠</sub> = -111 ± 5 J K<sup>-1</sup> mol<sup>-1</sup>. The reaction showed base catalysis and was also catalyzed by both CrO<sub>4</sub><sup>2-</sup> and acrylamide. It was inhibited by the oxidants WO<sub>4</sub><sup>2-</sup>, MoO<sub>4</sub><sup>2-</sup>, VO<sub>3</sub><sup>-</sup> and [Fe(CN)<sub>6</sub>]<sup>3-</sup> as well as by the reductants [Fe(CN)<sub>6</sub>]<sup>4-</sup> and D-mannitol, whereas Zn<sup>2+</sup> 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)<sub>6</sub>]<sup>4-</sup> and D-mannitol). <p>

Title:A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction
Creators:
Perez-Benito, Joaquin F.
Uncontrolled Keywords:Kinetics, Mechanism, Cytochrome <i>c</i>, Hydroxyl radicals, Proteins, Oxidative degradation, UV-VIS spectroscopy, Hydrogen peroxide
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:71
Number:11-12
Page Range:pp. 1588-1610
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20061588UNSPECIFIED
ID Code:2564
Item Type:Article
Deposited On:06 Feb 2009 17:19
Last Modified:06 Feb 2009 16:19

Citation

Perez-Benito, Joaquin F. (2006) A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction. Collection of Czechoslovak Chemical Communications, 71 (11-12). pp. 1588-1610. ISSN 0010-0765

Repository Staff Only: item control page