The
charge relay system in chymotrypsin is a mechanism that activates the serine residue to perform nucleophilic attack on the peptide bond during protein digestion. This system involves a catalytic triad of three amino acids: Serine (Ser), Histidine (His), and Aspartate (Asp). The mechanism works as follows:
- Aspartate forms a hydrogen bond with Histidine, stabilizing its positive charge.
- Histidine acts as a base and accepts a proton from the hydroxyl group of Serine.
- This deprotonation activates Serine to become a highly reactive nucleophile.
- The activated serine then attacks the carbonyl carbon of the peptide bond, leading to its cleavage.
This relay of charges between Asp, His, and Ser effectively enhances the enzymeβs catalytic activity by preparing the serine residue for proteolysis.