Understanding how enzymes work: the journey to ensemble-function studies.

Area of Science:

• Biochemistry
• Enzyme kinetics
• Structural biology

Background:

• Traditional descriptions of serine protease mechanisms, like the 'catalytic triad' and 'oxyanion hole', do not fully explain their immense rate enhancements (~10^12-fold).
• A deeper understanding of the physical and chemical interactions within enzyme active sites is needed to quantitatively account for catalytic efficiency.

Purpose of the Study:

• To develop and present a framework of ensemble-function analyses for quantitatively dissecting enzyme catalysis.
• To identify and quantify the contributions of specific molecular features in serine proteases that enable high catalytic efficiency.

Main Methods:

• Analysis of basic physical and chemical interactions in serine protease active sites.
• Application of statistical mechanics principles to quantify the contributions of individual catalytic features.
• Development of a 'catalytic ledger' to provide a quantitative accounting of enzyme catalysis.

Main Results:

• Identified previously unrecognized catalytic interactions, including destabilizing ground-state features (unfavorable rotamers, suboptimal distances/bonds), which are relieved in the transition state.
• Quantified the contributions of these features, revealing how they collectively lower the activation barrier for enzymatic reactions.
• Observed analogous catalytic features across diverse enzymes from different families and folds, suggesting convergent evolution.

Conclusions:

• Ensemble-function analyses provide a quantitative method to dissect enzyme catalysis, moving beyond simplified textbook models.
• These analyses reveal that enzymes utilize destabilizing ground-state interactions that are resolved in the transition state to achieve high catalytic efficiency.
• The identified strategies are broadly applicable across various enzymes and can inform future research on enzyme mechanisms, allostery, and molecular machines.