In enzymology, a tryptophan 2'-dioxygenase () is an enzyme that catalyzes the chemical reaction
<div align=center><small>L-tryptophan + + (indol-3-yl)glycolaldehyde + + </small></div>
Thus, the 3 substrates of this enzyme are L-tryptophan, and , whereas its 3 products are (indol-3-yl)glycolaldehyde, , and .
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 miscellaneous.
The systematic name of this enzyme class is L-tryptophan:oxygen 2'-oxidoreductase (side-chain-cleaving). Other names in common use include indole-3-alkane alpha-hydroxylase, tryptophan side-chain alpha,beta-oxidase, tryptophan side chain oxidase II, tryptophan side-chain oxidase, TSO, indolyl-3-alkan alpha-hydroxylase, tryptophan side chain oxidase type I, TSO I, TSO II, and tryptophan side chain oxidase.
This enzyme participates in tryptophan metabolism. It employs one cofactor, heme.