Intra- and extradiol dioxygenases are Fe-containing enzymes which catalyze the aromatic ring cleavage of catechols. Intradiol dioxygenases contain Fe³⁺ and cleave between the two hydroxyls of the catechol while extradiols cleave outside the hydroxyls and contain Fe²⁺. These dioxygenases show high specificity for their particular type of cleavage.

My project looks at homoprotocatechuate 2,3-dioxygenase (HPCD), an extradiol dioxygenase. Mutation of the second sphere residue H200F converts HPCD to do intradiol chemistry with the substrate 2,3-dihydroxybenzoate. I am using magnetic circular dichroism to study both the resting and substrate-bound complexes of the wild type and mutant enzymes.