Intermediates in dioxygen activation by methane monooxygenase: a QM/MM study

Area of Science:

• Biochemistry
• Computational Chemistry
• Enzymology

Background:

• Methane monooxygenase (MMO) is crucial for methane oxidation.
• Understanding the role of protein environment in enzymatic catalysis is vital.
• Accurate computational models are needed to elucidate complex reaction mechanisms.

Purpose of the Study:

• To investigate the influence of protein environment on dioxygen activation by MMO.
• To evaluate a novel empirical scheme for DFT energy calculations.
• To compare computational results with experimental data for key intermediates.

Main Methods:

• Combined Quantum Mechanics/Molecular Mechanics (QM/MM) simulations.
• Broken-symmetry Density Functional Theory (DFT) calculations.
• Analysis of electronic structure and geometric parameters.

Main Results:

• Protein inclusion significantly improved agreement with experimental structures for the reduced MMO (MMOH(red)).
• Distinct electronic environments were found for the two iron atoms in MMOH(red).
• The mu-eta2,eta2 coordination geometry is the most stable for the MMOH(peroxo) intermediate within the protein.

Conclusions:

• The protein environment plays a critical role in stabilizing intermediates and guiding the reaction pathway of MMO.
• QM/MM approaches are effective for accurate modeling of enzymatic reactions.
• Further investigation is needed to explain discrepancies in calculated Fe-Fe distances.