In enzymology, a peptide-tryptophan 2,3-dioxygenase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are peptide tryptophan and O<sub>2</sub>, whereas its product is peptide formylkynurenine.
This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O<sub>2</sub> as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O<sub>2</sub>. The systematic name of this enzyme class is peptide-tryptophan:oxygen 2,3-oxidoreductase (decyclizing). Other names in common use include pyrrolooxygenase, peptidyltryptophan 2,3-dioxygenase, and tryptophan pyrrolooxygenase.