Chloroperoxidase compound I: Electron paramagnetic resonance and Mössbauer studies

Area of Science:

• Biochemistry
• Enzymology
• Spectroscopy

Background:

• Chloroperoxidase plays a crucial role in oxidative catalysis.
• Understanding its reactive intermediates is key to elucidating enzyme mechanisms.

Purpose of the Study:

• To characterize the structure and electronic properties of chloroperoxidase compound I.
• To elucidate the nature of the ferryl iron and porphyrin radical interactions.

Main Methods:

• Preparation of chloroperoxidase compound I via freeze-quenching.
• Electron Paramagnetic Resonance (EPR) spectroscopy to analyze spin states.
• Mössbauer spectroscopy to determine iron electronic properties.

Main Results:

• EPR spectra indicated signals for native enzyme, a free radical, and compound I.
• Compound I exhibited an effective spin Seff = 1/2 with specific g-values.
• Mössbauer data revealed a spin S = 1 ferryl iron coupled to a spin S' = 1/2 porphyrin radical.

Conclusions:

• The data support a model of an exchange-coupled ferryl iron and porphyrin radical.
• Zero-field splitting and exchange interactions define the system's energy levels.
• The study provides detailed parameters for the ferryl iron and porphyrin radical in compound I.