pH dependence of carbon monoxide binding to ferrous horseradish peroxidase

The kinetic parameters of the reaction of horseradish peroxidase with CO have been determined at pH values between 10 and 3. At pH 7.0 the CO binding equilibrium constant L was measured using submicromolar concentrations of horseradish peroxidase; the value obtained corresponds to the ratio of the a...

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Bibliographic Details
Published inThe Journal of biological chemistry Vol. 261; no. 21; pp. 9811 - 9814
Main Authors Coletta, M, Ascoli, F, Brunori, M, Traylor, T G
Format Journal Article
LanguageEnglish
Published Bethesda, MD Elsevier Inc 25.07.1986
American Society for Biochemistry and Molecular Biology
Subjects
Analytical, structural and metabolic biochemistry
Biological and medical sciences
Carbon Monoxide - metabolism
Circular Dichroism
Enzymes and enzyme inhibitors
Ferrous Compounds - metabolism
Fundamental and applied biological sciences. Psychology
Hemeproteins - metabolism
Horseradish Peroxidase - metabolism
Hydrogen-Ion Concentration
Iron - metabolism
Kinetics
Oxidoreductases
Peroxidases - metabolism
Horse radish
Vegetals
Ligand
Oxidoreductase
Carbon dioxide
Dependence
PH
Molecular interaction
Peroxidase
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Summary:The kinetic parameters of the reaction of horseradish peroxidase with CO have been determined at pH values between 10 and 3. At pH 7.0 the CO binding equilibrium constant L was measured using submicromolar concentrations of horseradish peroxidase; the value obtained corresponds to the ratio of the association and dissociation kinetic constants as expected for a simple binding mechanism to a monomeric hemeprotein. The CO association rate constant is pH-independent below pH 7, whereas in going from pH 7 to pH 11 a 2-fold increase can be detected, as previously reported (Kertesz, D., Antonini, E., Brunori, M., Wyman, J., and Zito, R. (1965) Biochemistry 4, 2672-2676). On the other hand, CO dissociation displays a peculiar pH rate profile characterized by a progressive decrease from pH 10 to pH 5 and by a very marked increase as the pH is further lowered to pH congruent to 3. Furthermore, the rate of CO dissociation is markedly enhanced in peroxidase reconstituted with protoheme dimethyl ester, suggesting a role of the propionates in the regulation of this process.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)67587-8