This class of enzymes incorporate dioxygen into the substrate.
Catechol dioxygenases belong to the class of oxidoreductases and have several different substrate specificities, including catechol 1,2-dioxygenase (EC 1.13.11.1), catechol 2,3-dioxygenase (EC 1.13.11.2), and protocatechuate 3,4-dioxygenase (EC 1.13.11.3).
The active site of catechol dioxygenases most frequently contains iron, but manganese-containing forms are also known.
The Pseudomonas putida xylE gene, which encodes catechol 2,3-dioxygenase, is often used as a reporter to quantitate gene expression.
An example of the reaction carried out by catechol 1,2-dioxygenase is the formation of cis,cis-muconic acid from catechol, shown below.