Translations:Enzyme/35/en
Enzymes can accelerate reactions in several ways, all of which lower the activation energy (ΔG‡, Gibbs free energy)
- By stabilizing the transition state:
- Creating an environment with a charge distribution complementary to that of the transition state to lower its energy
- By providing an alternative reaction pathway:
- Temporarily reacting with the substrate, forming a covalent intermediate to provide a lower energy transition state
- By destabilising the substrate ground state:
- Distorting bound substrate(s) into their transition state form to reduce the energy required to reach the transition state
- By orienting the substrates into a productive arrangement to reduce the reaction entropy change (the contribution of this mechanism to catalysis is relatively small)
Enzymes may use several of these mechanisms simultaneously. For example, proteases such as trypsin perform covalent catalysis using a catalytic triad, stabilise charge build-up on the transition states using an oxyanion hole, complete hydrolysis using an oriented water substrate.