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Entry M0175    3.4.23.16    HIV-1 retropepsin

Next Step

Step 01

Asp25A deprotonates water, which then attacks the carbonyl carbon of the peptide bond in a nucleophilic addition, the resulting oxyanion then deprotonates Asp25B.

GIF of Reaction Step M0175.stg01


Comment: Catalytic aspartate residues have been shown to have different pKa values of 3.1 and 5.2, consistent with protonation of one catalytic residue. NMR measurements have also indicated that one of the two residues is protonated [4]. High resolution crystal structures suggest that the protonation states shown here are the correct ones [4].



Mechanisms

Proton Transfer
Bimolecular Nucleophilic Addition

Mechanism Components

Overall Reactant Used
Bond Formation
Bond Order Change
Bond Cleavage
Intermediate Formation

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Asp25A Side Chain reactant Hydrogen Bond Acceptor
Proton Acceptor
Gly27A Main Chain Amide spectator Hydrogen Bond Donor
Asp25B Side Chain reactant Hydrogen Bond Acceptor
Hydrogen Bond Donor
Proton Donor
Gly27B Main Chain Amide spectator Hydrogen Bond Donor
Electrostatic Stabiliser

Reactive Centre

Bonds Formed Bonds Cleaved Bonds Changed in Order Atom Types Involved
C-O
O-H
O-H
O-H
O-H
The C-O bond changes from a double to single bond
C
H
O

View similar reactions in MACiE.


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