CHEM 3050 Lecture Notes - Lecture 31: Scissile Bond, Oxyanion Hole, Glycolysis
3 May 2018
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CHEM 3050
Lecture 31
- Example: Chymotrypsin Mechanism
1. O atom of Ser195 has a Nucleophilic attack on
Carbonyl C which leads to formation of tetrahedral
geometry of the transition state
2. Now the anionic O “fits” into oxyanion hole (O is
not in the right place)
3. O forms a H-bond with the backbone NH of Ser195
and Gly193
4. Another H-bond from Gly193 is formed with NH
preceding the scissile bond of the substrate
o High Energy of the transition state is lowered by
forming the 3 H-bonds
o H-bonding is the primary source for stabilization
o Lowering the energy hill is the secondary source
for stabilization (Low barrier H-bond: shorter
the bond, the stronger it is)
In order for the Enzymes to have an Effect:
- It is important that they are closed in proximity, and
has proper orientation.
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