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Entry M0192    5.3.99.3    prostaglandin-E synthase

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Step 03

A hydroxide ion deprotonates the C9 of the covalently bound intermediate initiating an elimination reaction that releases the thiolate form of Cys110 and the prostaglandin E2 product

GIF of Reaction Step M0192.stg03


Comment: An R-SH (or a water) bound between OH of Tyr107 and C9 of PGH2 is polarised by forming a H-bond with Tyr107, and consequently, the thiol group of R-SH (or water) is deprotonated at neutral pH. The resulting thiolic anion (or hydroxyl anion) removes the hydrogen atom attached to C9 [1].



Mechanisms

Bimolecular Elimination

Mechanism Components

Bond Formation
Bond Cleavage
Enzyme-Substrate Bond Cleavage
Bond Order Change
Intermediate Collapse
Intermediate Terminated
Intermediate Formation
Overall Product Formed

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Tyr107A Side Chain spectator Hydrogen Bond Donor
Electrostatic Stabiliser
Tyr107A Main Chain Amide spectator Hydrogen Bond Donor
Cys113 Side Chain spectator Hydrogen Bond Donor
Hydrogen Bond Acceptor
Electrostatic Stabiliser
Cys110 Side Chain reactant Nucleofuge
Hydrogen Bond Acceptor
Phe112 Main Chain Amide spectator Hydrogen Bond Donor
Electrostatic Stabiliser

Reactive Centre

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

View similar reactions in MACiE.


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