Understanding the Directed Evolution of a Natural-like Efficient Artificial Metalloenzyme

Area of Science:

• Biocatalysis and enzyme engineering
• Computational chemistry and molecular modeling
• Bioinorganic chemistry

Background:

• Artificial metalloenzymes merge biocatalyst efficiency with small molecule catalyst versatility.
• Directed evolution has yielded a novel iridium-containing cytochrome P450 with high catalytic efficiency for carbene insertion.
• The mechanistic and structural basis for the enhanced efficiency of these engineered enzymes remains poorly understood.

Purpose of the Study:

• To elucidate the atomistic mechanisms by which directed evolution mutations enhance catalytic activity in an artificial metalloenzyme.
• To understand how protein conformational ensembles and active site dynamics contribute to catalysis.
• To provide insights for the rational design of future artificial enzymes with improved efficiency.

Main Methods:

• Large-scale molecular dynamics (MD) simulations.
• Rigorous quantum chemical (QM) calculations.
• Multiscale QM/MM calculations.

Main Results:

• Directed evolution mutations alter the protein's conformational ensemble, favoring a catalytically active state.
• Mutations L69V and V254L stabilize an unusual cofactor-substrate orientation via C-H···π interactions, enhancing transition state stabilization.
• The active conformation accurately reproduces experimental catalytic barriers and highlights the role of non-electrostatic interactions.

Conclusions:

• Directed evolution fine-tunes enzyme active sites to optimize conformational dynamics and transition state stabilization.
• Non-electrostatic interactions play a critical role in the catalytic efficiency of this artificial metalloenzyme.
• This study offers a detailed mechanistic understanding valuable for designing highly efficient artificial enzymes.