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Measured change in protein solvation with substrate binding and turnover
R P Rand1, N L Fuller, P Butko
1Brock University, St. Catharines, Ontario, Canada.
Biochemistry
|June 15, 1993
Summary
Osmotic stress reveals that hexokinase releases approximately 65 water molecules during glucose binding. This dehydration/rehydration process significantly impacts enzyme energetics and conformational changes during turnover.
Area of Science:
- Biochemistry
- Biophysical Chemistry
Background:
- Enzyme activity is influenced by solvation and conformational changes.
- Understanding water's role in enzyme function is crucial for biophysical chemistry.
Purpose of the Study:
- To quantify solvation changes during enzyme conformational changes using osmotic stress.
- To investigate the energetic contribution of water release/uptake in enzyme turnover.
Main Methods:
- Utilized osmotic stress with high molecular weight osmolytes to alter water activity.
- Measured changes in hexokinase's equilibrium dissociation constant and Michaelis-Menten constant for glucose.
- Correlated kinetic and equilibrium parameters with water activity.
Main Results:
- Hexokinase's glucose binding and catalytic constants varied linearly with water activity.
- Glucose binding is associated with the release of approximately 65 water molecules.
- Water release is reversed upon enzyme turnover, suggesting a significant energetic contribution.
Conclusions:
- Solvation changes, particularly water release/uptake, play a major role in enzyme conformational dynamics.
- Osmotic stress is a versatile technique for studying water's contribution to molecular function.
- The findings highlight the dynamic interplay between hydration and enzyme catalysis.