Tryptophan 2-monooxygenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are L-tryptophan and oxygen. Its products are 3-indoleacetamide, carbon dioxide, and water.
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 with incorporation of one atom of oxygen (internal monooxygenases o internal mixed-function oxidases). The systematic name of this enzyme class is L-tryptophan:oxygen 2-oxidoreductase (decarboxylating). This enzyme participates in tryptophan metabolism, especially in plants, where the product amide can be converted to the auxin hormone indole-3-acetic acid.
Like other similar enzymes which use oxygen to cleave amino acids, this is a flavoprotein. Others include lysine 2-monooxygenase and arginine 2-monooxygenase.