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Entry M0284    3.5.5.8    thiocyanate hydrolase

Next Step

Step 01

Tyr108 activates a water molecule towards nucleophilic attack on the Co(III) coordinated thiocyanate substrate.

GIF of Reaction Step M0284.stg01


Comment: It is unknown whether the post translational hydroxylation of Cys133 results in a protonated hydroxyl or anionic hydroxide functionality [3].
Crystallographic data suggests Co(III) forms a pentavalent coordination environment. The distal position is seen not to coordination to water, as is the case for the related enzyme Nitrile hydrolase, but instead binds the thiocyanate substrate via its nitrogen. The metal centre acts as a Lewis acid, increasing the electrophilic character of the bound thiocyanate [1].
Both Tyr108 and Cys133 have been identified as hydrolysis activating residues, although their precise roles are only partially characterised [1].



Mechanisms

Proton Transfer
Bimolecular Nucleophilic Addition

Mechanism Components

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

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Ser132C Side Chain spectator Metal Ligand
Electrostatic Stabiliser
Activator
Ser132C Main Chain Amide spectator Metal Ligand
Electrostatic Stabiliser
Activator
Cys128C Side Chain spectator Metal Ligand
Electrostatic Stabiliser
Activator
Cso133C Main Chain Amide spectator Metal Ligand
Electrostatic Stabiliser
Activator
Cso133C Post-Translationally Modified Residue spectator Metal Ligand
Electrostatic Stabiliser
Activator
Tyr108C Side Chain reactant Hydrogen Bond Acceptor
Proton Acceptor
Csd131C Post-Translationally Modified Residue spectator Metal Ligand
Electrostatic Stabiliser
Activator

Metal Cofactors involved in Step 01

Metal Type Metal Identity Chain Activity Function
cobalt 3CO 301 C spectator Activator
Substrate Binding
Increase Electrophilicity

Reactive Centre

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

View similar reactions in MACiE.


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