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Entry M0060    3.5.99.6    glucosamine-6-phosphate deaminase

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Step 04

In an electrophilic reaction, water is added across the C1-C2 pi bond.

GIF of Reaction Step M0060.stg04


Comment: There are two alternative mechanism for this step. The proton from the ammonium group could be transferred to the Asp72 carboxylate. The resulting cis-enolamine then removes the proton from Asp72 to the position C1 pro-R of the intermediate which rearranges to form fructosimine 6-phosphate. The imino bond reacts with a water molecule, giving an unstable carbinol ammonium intermediate. Alternatively, shown here, the pi-bond (C1-C2) of the cis-enol-ammonium is attacked by a water molecule coming from the re-face of the intermediate (i.e. from the same side as Asp72) [1].



Mechanisms

Bimolecular Electrophilic Addition

Mechanism Components

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

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
His143 Side Chain spectator Hydrogen Bond Acceptor
Hydrogen Bond Donor
Asp72 Side Chain spectator Electrostatic Stabiliser
Hydrogen Bond Acceptor
Glu148 Side Chain spectator Hydrogen Bond Acceptor
Asp141 Side Chain spectator Hydrogen Bond Acceptor

Reactive Centre

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

View similar reactions in MACiE.


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