Ensemble-function relationships to dissect mechanisms of enzyme catalysis

Area of Science:

• Biochemistry and Structural Biology
• Enzyme Kinetics and Catalysis

Background:

• Enzyme structure-function relationships are extensively studied, but traditional models offer static snapshots.
• Enzymes exist as dynamic conformational ensembles, crucial for understanding their catalytic mechanisms.
• Static models can lead to misinterpretations of mutational effects on enzyme function.

Purpose of the Study:

• To demonstrate the necessity of conformational ensembles for a comprehensive understanding of enzyme function.
• To utilize ketosteroid isomerase (KSI) as a model system to investigate enzyme dynamics.
• To differentiate between effects altering state probability (P-effects) and state reactivity (k-effects).

Main Methods:

• Comparative analysis of cryogenic X-ray crystallography structures versus room-temperature X-ray crystallography.
• Integration of ensemble information with functional biochemical studies.
• Ensemble-function analysis to dissect P-effects and k-effects.

Main Results:

• Ensemble data from room-temperature crystallography, combined with functional studies, refuted previous models based on static structures.
• Ensemble-function analysis identified weakened oxyanion hole hydrogen bonding as a key factor.
• Substrate repositioning within the active site was revealed as a significant functional consequence of enzyme dynamics.

Conclusions:

• Conformational ensembles are essential for accurately interpreting enzyme structure-function relationships.
• Ensemble-function studies provide deeper insights into catalytic mechanisms than static models.
• This approach is critical for advancing predictive enzyme catalysis and enzyme engineering.