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Heme structural perturbation of PEG-modified horseradish peroxidase C in aromatic organic solvents probed by optical absorption and resonance Raman dispersion spectroscopy
Journal article   Open access   Peer reviewed

Heme structural perturbation of PEG-modified horseradish peroxidase C in aromatic organic solvents probed by optical absorption and resonance Raman dispersion spectroscopy

Qing Huang, Wasfi Al-Azzam, Kai Griebenow and Reinhard Schweitzer-Stenner
Biophysical journal, v 84(5), pp 3285-3298
May 2003
DOI: https://doi.org/10.1016/S0006-3495(03)70053-8
PMID: 12719258
Featured in Collection :   UN Sustainable Development Goals @ Drexel
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https://doi.org/10.1016/S0006-3495(03)70053-8View
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Abstract

Solvents - chemistry Organic Chemicals - chemistry Models, Molecular Substrate Specificity Polyethylene Glycols - chemistry Spectrum Analysis, Raman - methods Horseradish Peroxidase - chemistry Toluene - chemistry Hydrocarbons, Aromatic - chemistry Heme - chemistry Solutions Benzene - chemistry Protein Binding Protein Conformation Enzyme Activation Binding Sites
The heme structure perturbation of poly(ethylene glycol)-modified horseradish peroxidase (HRP-PEG) dissolved in benzene and toluene has been probed by resonance Raman dispersion spectroscopy. Analysis of the depolarization ratio dispersion of several Raman bands revealed an increase of rhombic B(1g) distortion with respect to native HRP in water. This finding strongly supports the notion that a solvent molecule has moved into the heme pocket where it stays in close proximity to one of the heme's pyrrole rings. The interactions between the solvent molecule, the heme, and the heme cavity slightly stabilize the hexacoordinate high spin state without eliminating the pentacoordinate quantum mixed spin state that is dominant in the resting enzyme. On the contrary, the model substrate benzohydroxamic acid strongly favors the hexacoordinate quantum mixed spin state and induces a B(2g)-type distortion owing to its position close to one of the heme methine bridges. These results strongly suggest that substrate binding must have an influence on the heme geometry of HRP and that the heme structure of the enzyme-substrate complex (as opposed to the resting state) must be the key to understanding the chemical reactivity of HRP.

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Web of Science research areas
Biophysics
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