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Entry M0178    3.6.3.14    H+-transporting two-sector ATPase

Next Step

Step 01

The gamma phopshate of ATP deprotonates the first water, which deprotonates a second water, which attacks the gamma phosphate in a nucleophilic addition resulting in a pentavalent phosphate intermediate.

Rate Determining Step

GIF of Reaction Step M0178.stg01


Comment: The proton of the nucleophilic water is first transferred to the other water molecule (non-nucleophilic) that then donates its proton to the gamma-oxygen of ATP to complete the proton transfer. This leads to a oxonium in the transition state. Computational studies suggest that this is the rate-determining step and that Arg373C electrostatically stabilises the phosphate and Glu188 stabilises the oxonium in the transition state [1].



Mechanisms

Proton Transfer
Bimolecular Nucleophilic Addition

Mechanism Components

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

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Arg373C Side Chain spectator Hydrogen Bond Donor
Electrostatic Stabiliser
Lys162 Side Chain spectator Hydrogen Bond Donor
Electrostatic Stabiliser
Glu188 Side Chain spectator Hydrogen Bond Acceptor
Electrostatic Stabiliser
Arg189 Side Chain spectator Hydrogen Bond Donor
Electrostatic Stabiliser

Metal Cofactors involved in Step 01

Metal Type Metal Identity Chain Activity Function
magnesium MG 601 A spectator Substrate Binding
Activator
Increase Electrophilicity
Electrostatic Stabiliser

Reactive Centre

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

View similar reactions in MACiE.


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