Organophosphate Hydrolysis by a Designed Metalloenzyme: Impact of Mutations Explained

Area of Science:

• Biochemistry
• Computational Chemistry
• Enzyme Engineering

Background:

• De novo enzyme design requires integrating theoretical and experimental methods for optimal performance.
• Existing de novo design protocols often show inadequate results, necessitating improved theoretical models.
• Understanding enzyme-catalytic mechanisms, including ground state (GS) and transition state (TS) interactions, is crucial for rational design.

Purpose of the Study:

• To develop and validate improved theoretical models for enzyme catalytic activity.
• To investigate the role of ground state destabilization versus transition state stabilization in enzyme catalysis.
• To assess the impact of side chain rotamer selection on enzyme design accuracy.

Main Methods:

• Analysis of the evolutionary trajectory of a designed organophosphate hydrolase.
• Calculation of differential transition state stabilization (DTSS) using a non-empirical model (MED: multipole electrostatic plus approximate dispersion terms).
• Systematic rotamer refinement incorporating long-range interaction energy terms and efficient scanning procedures.

Main Results:

• The MED-based DTSS approach demonstrated superior performance in ranking the catalytic activity of five enzyme variants.
• Systematic rotamer refinement using MED DTSS unlocked the full potential impact of amino acid residues, surpassing conventional static approaches.
• Transition state stabilization was identified as the primary driver of increased catalytic activity in the de novo-designed variant.

Conclusions:

• Improved theoretical models, particularly MED-based DTSS with systematic rotamer refinement, significantly enhance de novo enzyme design.
• The study highlights the importance of accurately modeling enzyme-reactant interactions, including both GS and TS stabilization.
• Directed evolution can influence enzyme activity through ground state destabilization, complementing transition state stabilization strategies.