Electric fields imbue enzyme reactivity by aligning active site fragment orbitals

Area of Science:

• Biochemistry
• Computational Chemistry
• Enzymology

Background:

• Enzymatic catalysis is facilitated by intramolecular electric fields from protein scaffolds.
• Existing theoretical models for this field effect vary in intuitiveness.
• Understanding the precise mechanism of electric field influence is crucial for enzyme engineering.

Purpose of the Study:

• To present a fundamental model explaining how electric fields facilitate enzymatic catalysis through electrostatic potentials.
• To apply this model to high-valent iron-oxo heme proteins (catalases, peroxidases, peroxygenases/monooxygenases).
• To provide a quantitative, single-parameter approach for assessing electric field effects on reactivity and selectivity.

Main Methods:

• Theoretical modeling of electrostatic potentials generated by electric fields.
• Analysis of reactant frontier orbital energetic alignment.
• Application to high-valent iron-oxo heme protein active site models, including Cytochrome P450.
• Assessment of spin distribution changes and reaction pathway transitions.

Main Results:

• Electric fields generate electrostatic potentials that energetically align reactant frontier orbitals.
• The model successfully explains field-induced spin distribution changes in peroxidases.
• The model accounts for the shift between epoxidation and hydroxylation pathways in Cytochrome P450 models.
• Fragment orbital energy differences quantify chemical hardness/softness and its sensitivity to electric fields.

Conclusions:

• The energetic alignment of reactant orbitals by electrostatic potentials is a fundamental effect of electric fields in enzymatic catalysis.
• This single-parameter model offers an intuitive and quantitative method to understand and manipulate electrostatic preorganization in enzyme active sites.
• The findings provide new perspectives for designing enzymes with tailored reactivity and selectivity.