The beta subunit of the Class III extradiol dioxygenase, 2-amino-5-chlorophenol 1,6-dioxygenase, which catalyzes the oxidization and subsequent ring-opening of 2-amino-5-chlorophenol.
2-amino-5-chlorophenol 1,6-dioxygenase (2A5CPDO), catalyzes the oxidization and subsequent ring-opening of 2-amino-5-chlorophenol, which is an intermediate during p-chloronitrobenzene degradation. This enzyme is a member of the class III extradiol dioxygenase family, a group of enzymes which use a non-heme Fe(II) to cleave aromatic rings between a hydroxylated carbon and an adjacent non-hydroxylated carbon. The active 2A5CPDO enzyme is probably a heterotetramer, composed of two alpha and two beta subunits. The alpha and beta subunits share significant sequence similarity and may have evolved by gene duplication. This model describes the beta subunit, which contains a putative metal binding site with two conserved histidines; these residues are equivalent to two out of three Fe(II) binding residues present in the catalytic subunit dioxygenase LigB. The alpha subunit does not contain these potential metal binding residues. The 2A5CPDO beta subunit may be the catalytic subunit of the enzyme.