Abstract
The contribution of electrostriction of the solvent to the stabilization of the negatively charged tetrahedral transition state of a trypsin-catalyzed reaction was probed by means of kinetic studies involving high-pressure and solvent dielectric constant. A good correlation was observed between the increased catalytic efficiency of trypsin and the decreased solvent dielectric constant. When the dielectric constant of the solvents was lowered by 4.68 units, the loss of activation energy and that of free energy of activation were 2.26 kJ/mol and 3.09 kJ/mol, respectively. The activation volume for kcat decreased significantly as the dielectric constant of the solvent decreased, indicating that the degree of electrostriction of the solvent around the charged tetrahedral transition state has been enhanced. These observations demonstrate that the increase in the catalytic efficiency of the trypsin reaction with decreasing dielectric constant resulted from the stabilization of electrostatic energy for the formation of an oxyanion hole, and this stabilization was caused by the increase of electrostricted water around the charged tetrahedral transition state. Therefore, we conclude that control of the solvent dielectric constant can stabilize the tetrahedral transition state, and this lowers the activation energy.
Original language | English |
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Pages (from-to) | 53-59 |
Number of pages | 7 |
Journal | Biochimica et Biophysica Acta - General Subjects |
Volume | 1568 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2001 Nov 7 |
Keywords
- Activation volume
- Dielectric constant
- Electrostriction
- High-pressure kinetics
- Tetrahedral transition state
- Trypsin
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Molecular Biology