Studies on the regioselectivity and stereoselectivity of the soluble methane monooxygenase from methylococcus capsulatus (Bath)

Alkyl substituted derivatives of cyclohexane and cyclohexene have been used as active site probes of the soluble methane monooxygenase (MMO) from Methylococcus capsulatus (Bath). It is proposed that the products obtained are those that would be predicted on the grounds of chemical reactivity modulated by two enzymic constraints (i) steric hindrance favouring hydroxylation at positions distal to bulky substituents and (ii) limited penetration of the substrate beyond the active site of oxygen insertion. Evidence for inversion of stereochemistry during the hydroxylation of cis-dimethylcyclohexane and rearrangement during the hydroxylation of 3-methyl-1-cyclohexene supports the suggestion that a stepwise mechanism (hydrogen abstraction and hydroxylation) operates in the hydroxylation of aliphatic carbons.