Dioxygenase

In molecular biology, a dioxygenase is an enzyme which catalyses the incorporation of both atoms of molecular oxygen into substrates using a variety of reaction mechanisms. Cleavage of aromatic rings is one of the most important functions of dioxygenases, which play key roles in the degradation of aromatic compounds. The substrates of ring-cleavage dioxygenases can be classified into two groups according to the mode of scission of the aromatic ring. Intradiol enzymes use a non-haem Fe(III) to cleave the aromatic ring between two hydroxyl groups (ortho-cleavage), whereas extradiol enzymes use a non-haem Fe(II) to cleave the aromatic ring between a hydroxylated carbon and an adjacent non-hydroxylated carbon (meta-cleavage). These two subfamilies differ in sequence, structural fold, iron ligands, and the orientation of second sphere active site amino acid residues.

Enzymes that belong to the intradiol family include catechol 1,2-dioxygenase (1,2-CTD) ; protocatechuate 3,4-dioxygenase (3,4-PCD) and chlorocatechol 1,2-dioxygenase

Enzymes that belong to the extradiol class II family include catechol 2,3-dioxygenase (2,3-CTD) and biphenyl-2,3-diol 1,2-dioxygenase (BphC).