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Leaving Group Ability Observably Affects Transition State Structure in a Single Enzyme Active Site
Daniel Roston1, Darren Demapan1, Qiang Cui1
1Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin , Madison, Wisconsin 53706, United States.
Journal of the American Chemical Society
|May 18, 2016
Summary
Enzyme active sites show remarkable flexibility, adapting transition state (TS) structures to stabilize substrates. This plasticity impacts enzyme reactivity and how experimental probes influence observed results.
Area of Science:
- Biochemistry
- Computational Chemistry
- Enzymology
Background:
- The transition state (TS) structure is crucial for enzyme reactivity and influences the design of catalysts and drugs.
- Understanding how enzymes stabilize the TS is key to deciphering reaction mechanisms.
Purpose of the Study:
- To investigate the transition state (TS) structure of the enzyme alkaline phosphatase.
- To explore how substrate modifications affect TS stabilization within the enzyme's active site.
Main Methods:
- Hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) simulations were employed.
- The study focused on analyzing the structural and electronic properties of the TS for different substrates.
Main Results:
- Minor substrate changes significantly alter TS structure and enzyme stabilization mechanisms.
- Substrates with poor leaving groups (LGs) exhibit greater phosphorus-LG bond cleavage at the TS compared to those with good LGs.
- The enzyme stabilizes poor LGs via a zinc ion, while good LGs are stabilized by water molecules.
Conclusions:
- Enzyme TS structures display considerable plasticity and varied stabilization strategies.
- Experimental probes of TS structure may inadvertently alter the TS, necessitating careful interpretation of classical methods like free energy relationships.
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