Entry M0254 184.108.40.206 squalene-hopene cyclase
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The water molecule polarised by Glu45 abstracts the proton or attacks the E-ring cation, to terminate the reaction.
Comment: Finally, the enzyme reaction is terminated by either regiospecific elimination of the Z-methyl group to the major product hop-22(29)-ene (80%), alternatively, addition of water forms the minor product hopan-22-ol (20%). It has been proposed that the water molecules are polarized by residues in the hydrogen-bonding network around Glu45 at the bottom of the active-site cavity; a polarized water molecule abstracts the proton or attacks the E-ring cation, to terminate the reaction. In fact, the product ratio of hopene and hopanol has been reported to be significantly altered in E45A and E45D mutants of A. acidocaldarius SHC .
Amino acids involved in the reaction step.
||Bonds Changed in Order
||Atom Types Involved
The C-C bond changes from a single to double bond
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