Methods for Efficiently and Accurately Computing Quantum Mechanical Free Energies for Enzyme Catalysis.

Area of Science:

• Biochemistry
• Computational Chemistry
• Enzymology

Background:

• Enzyme activity is governed by free energies of transition states and ligand binding.
• Predicting these free energies is crucial for understanding enzyme function, but computationally challenging.
• Accurate molecular simulations require precise interaction descriptions and conformational sampling.

Purpose of the Study:

• To present novel computational methods for Free Energy Simulations (FES) in enzymatic systems.
• To address limitations in existing hybrid quantum mechanics/molecular mechanics (QM/MM) approaches for reactive processes.
• To demonstrate the calculation of relative free energies and reaction path free energies.

Main Methods:

• Utilizing a hybrid quantum mechanics/molecular mechanics (QM/MM) framework.
• Implementing QM non-Boltzmann Bennett's acceptance ratio method.
• Applying QM nonequilibrium work method for free energy calculations.
• Incorporating explicit solvation and extensive conformational sampling.

Main Results:

• Overview of two new QM/MM FES methods.
• Demonstration of calculating relative free energies.
• Calculation of free energies along enzymatic reaction paths.
• Validation using simple test cases relevant to enzymes.

Conclusions:

• The presented QM/MM FES methods mitigate major challenges in simulating enzymatic processes.
• These methods enable more accurate predictions of enzyme function by calculating critical free energies.
• The approach facilitates a deeper understanding of enzyme mechanisms and the impact of mutations or allosteric effects.