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Entry M0254    5.4.99.17    squalene-hopene cyclase

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Step 02

The intermediate undergoes an intramolecular electrophilic addition in a Markovnikov-type cation–olefin addition.

GIF of Reaction Step M0254.stg02


Comment: A Markovnikov-type cation–olefin addition first produces a 6.6 bicyclic tertiary cation, which is stabilized by the pi-electrons and dipoles of aromatic residues including Phe365, Tyr420, Trp489, and Tyr609 [1].



Mechanisms

Intramolecular Electrophilic Addition

Mechanism Components

Bond Formation
Bond Order Change
Intermediate Formation
Cyclisation

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Asp376 Side Chain spectator Hydrogen Bond Acceptor
His451 Side Chain spectator Hydrogen Bond Donor
Electrostatic Stabiliser
Tyr495 Side Chain spectator Hydrogen Bond Donor
Electrostatic Stabiliser
Phe365 Side Chain spectator van der Waals interaction
Electrostatic Stabiliser
Tyr420 Side Chain spectator van der Waals interaction
Polar Non-polar interaction
Electrostatic Stabiliser
Trp489 Side Chain spectator van der Waals interaction
Polar Non-polar interaction
Electrostatic Stabiliser
Tyr609 Side Chain spectator van der Waals interaction
Polar Non-polar interaction
Electrostatic Stabiliser
Phe601 Side Chain spectator van der Waals interaction
Phe605 Side Chain spectator van der Waals interaction
Trp169 Side Chain spectator van der Waals interaction
Polar Non-polar interaction
Glu45 Side Chain spectator Hydrogen Bond Acceptor

Reactive Centre

Bonds Formed Bonds Cleaved Bonds Changed in Order Atom Types Involved
C-C
C-C
None
The C-C bond changes from a double to single bond
The C-C bond changes from a double to single bond
C

View similar reactions in MACiE.


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