   1.14.13.208 | benzoyl-CoA + NADPH + H+ + O2 = 2,3-epoxy-2,3-dihydrobenzoyl-CoA + NADP+ + H2O |
epoxidation starts with the binding of the O2 molecule to the diferrous center to generate a diferric peroxide complex, followed by concerted O-O bond cleavage and epoxide formation. Two different pathways have been located, leading to (2S,3R)-epoxy and (2R,3S)-epoxy products. The barrier difference is 2.8 kcal/mol, corresponding to a diastereomeric excess of about 99:1. Further isomerization from epoxide to phenol has quite a high barrier, which cannot compete with the product release step. After product release into solution, fast epoxide-oxepin isomerization and racemization can take place easily, leading to a racemic mixture of (2S,3R) and (2R,3S) products. The deoxygenation of epoxide to regenerate benzoyl-CoA by a diferrous form of the enzyme proceeds via a stepwise mechanism. The C2-O bond cleavage happens first, coupled with one electron transfer from one iron center to the substrate, to form a radical intermediate, which is followed by the second C3-O bond cleavage. The first step is rate-limiting. Reaction mechanism, modeling and simulations, detailed overview |
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