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Entry M0107    1.2.99.2    carbon-monoxide dehydrogenase (acceptor)

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Step 03

The sulfur dianion bridging the Mo(IV) and Cu(I) centres initiates a nucleophilic attack on the carbocation in a substitution reaction that displaces the carbon from the Cu(I) centre.

GIF of Reaction Step M0107.stg03


Comment: Upon inhibition with n-butylisocyanide (which mimics the product state of this step), the enzyme is Mo-EPR and Cu-EPR silent from temperatures of 16 to 120 K, suggesting that the oxidation states are +IV and +I respectively. These oxidation states are further supported by the shapes of the Mo- and Cu-K edges of the inactivated enzyme revealed by X-ray absorption spectroscopy [1].



Mechanisms

Intramolecular Nucleophilic Substitution

Mechanism Components

Bond Formation
Bond Cleavage
Metal De-coordination
Intermediate Formation

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Glu763 Side Chain spectator Not Active
Cys388 Side Chain spectator Metal Ligand
Electrostatic Stabiliser

Organic Cofactors involved in the reaction step

Cofactor Type Cofactor Activity Function
FAD FAD3932 spectator Not Active

Metal Cofactors involved in Step 03

Metal Type Metal Identity Chain Activity Function
iron FES 3907 x spectator Not Active
iron FES 3908 x spectator Not Active
copper CUB 3921 x spectator Activator
Substrate Binding
molybdenum CUB 3921 x spectator Substrate Binding

Reactive Centre

Bonds Formed Bonds Cleaved Bonds Changed in Order Atom Types Involved
C-S
Cu-C
None
C
Cu
S

View similar reactions in MACiE.


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