Conformational sampling, catalysis, and evolution of the bacterial phosphotriesterase

Area of Science:

• Biochemistry and enzymology
• Structural biology
• Chemical kinetics

Background:

• Enzymes require rapid substrate binding, catalysis, and product release for efficient function.
• Enzyme conformational dynamics are proposed to facilitate these distinct catalytic steps.
• The role of conformational substates (CSs) in enzyme catalysis remains debated.

Purpose of the Study:

• To investigate the role of conformational substates (CSs) in the catalytic mechanism of bacterial phosphotriesterase (PTE).
• To understand how enzyme dynamics influence substrate turnover, including binding and product release.
• To elucidate the relationship between enzyme structure, dynamics, and catalytic efficiency.

Main Methods:

• Studied bacterial phosphotriesterase (PTE) as a model system for enzyme catalysis.
• Identified distinct "open" and "closed" conformational substates (CSs) in PTE.
• Analyzed structural and kinetic effects of mutations distant from the active site.

Main Results:

• PTE exists in distinct open and closed CSs linked by a dominant structural transition.
• The closed CS is optimized for hydrolysis but restricts active site access.
• The open CS allows active site access but is less catalytically efficient.
• Remote mutations alter the enzyme's conformational landscape, affecting turnover rates.

Conclusions:

• Enzyme conformational dynamics, through distinct CSs, are crucial for balancing substrate access and catalytic efficiency.
• Bacterial phosphotriesterase (PTE) utilizes a conformational selection mechanism involving open and closed states.
• Allosteric regulation via remote mutations can modulate enzyme activity by altering the conformational landscape.