Add arrows and missing tetrahedral intermediates in mechanism. O ASP 176 OH Asp 176 N- His 263 H N N H -His263 Tetrahedral Intermediate Ser 152 ‘N 0 Ho Ser152 OAcyl OAcyl Phe77°N – 0 Phe77 N-H H R -N-R Leu 153 R H R H -N-R Leu 153 Asp 176 Asp 176 H H N но. His 263 -HiS263 ОАсу Acyl N H2O H Ser 152 0 OH 01 Ser 152 o НО. OAcyl O Acyl Phe77-N-H Phen-NH H R R H _N-R Leu 153 N-R Leu 153 Asp 176 OH Asp 178 N His 263 Tetrahedral Intermediate H ‘N H His263 OH HO Ser 152 -OH Phe77 N-H 0 H Phe77-N-H H R Leu153 -N-R R NA Leu753
The Correct Answer and Explanation is :
General Explanation of the Mechanism:
- Substrate Binding: The substrate (usually a peptide or protein) binds to the enzyme’s active site. The functional groups of the amino acids in the enzyme’s active site interact with the substrate.
- Nucleophilic Attack: Ser 152, a key nucleophile, attacks the carbonyl carbon of the substrate’s peptide bond. This forms a tetrahedral intermediate. The lone pair of electrons from the hydroxyl group of Ser 152 attacks the carbonyl carbon, creating a negatively charged oxygen.
- Tetrahedral Intermediate: The intermediate has a negative charge on the oxygen that was originally part of the peptide bond. This intermediate is often stabilized by hydrogen bonding with surrounding amino acids, such as His 263, which may help stabilize the negative charge.
- Formation of a New Bond: The bond between the substrate and the enzyme is temporarily broken as a new bond forms. This can involve the nucleophilic attack of water (H2O), which is activated by His 263. The water molecule attacks the intermediate, helping to release the substrate.
- Resolution: The hydrolyzed product is released, and the enzyme is restored to its original state, ready for another round of catalysis. This process can be repeated.
Key Amino Acid Roles:
- Ser 152: Nucleophile that initiates the attack.
- His 263: Proton donor/acceptor that aids in stabilizing the intermediate and activating water.
- Asp 176: Could be involved in stabilizing the charged intermediate.
- Phe 77 and Leu 153: Likely involved in substrate binding or maintaining the enzyme’s structural integrity.
If you want, I can generate an image illustrating the mechanism with arrows and intermediate structures based on these details! Let me know if you’d like me to proceed with that.