Absence of a Detectable Intermediate in the Compound I Formation of Horseradish Peroxidase at Ambient Temperature*
| Autor: | Koichiro Ishimori, Masato Shintaku, Isao Morishima, Satoshi Takahashi, Shiro Yoshioka, Koji Matsuura |
|---|---|
| Rok vydání: | 2005 |
| Předmět: |
Isosbestic point
Chemical Phenomena biology Absorption spectroscopy Chemistry Physical Chemistry Spectrum Analysis Temperature Hydrogen Peroxide Cell Biology Photochemistry Ferric Compounds Biochemistry Horseradish peroxidase Absorbance Kinetics chemistry.chemical_compound Reaction rate constant biology.protein Absorption (chemistry) Hydrogen peroxide Molecular Biology Horseradish Peroxidase Peroxidase |
| Zdroj: | Journal of Biological Chemistry. 280:40934-40938 |
| ISSN: | 0021-9258 |
| Popis: | A microsecond-resolved absorption spectrometer was developed to investigate the elementary steps in hydrogen peroxide (H(2)O(2)) activation reaction of horseradish peroxidase (HRP) at ambient temperature. The kinetic absorption spectra of HRP upon the mixing with various concentrations of H(2)O(2) (0.5-3 mm) were monitored in the time range from 50 to 300 mus. The time-resolved spectra in the Soret region possessed isosbestic points that were close to those between the resting state and compound I. The kinetic changes in the Soret absorbance could be well fitted by a single exponential function. Accordingly, no distinct spectrum of the putative intermediate between the resting state and compound I was identified. These results were consistent with the proposal that the O-O bond activation in heme peroxidases is promoted by the imidazolium form of the distal histidine that exists only transiently. It was estimated that the rate constant for the breakage of the O-O bond in H(2)O(2) by HRP is significantly faster than 1 x 10(4) s(-1). |
| Databáze: | OpenAIRE |
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