Heme-dependent dioxygenase that catalyzes the oxidative cleavage of the L-tryptophan (L-Trp) pyrrole ring and converts L-tryptophan to N-formyl-L-kynurenine. Catalyzes the oxidative cleavage of the indole moiety. L-tryptophan + O2 = N-formyl-L-kynurenine Binds 1 heme group per subunit. Stimulated by low concentrations of hydrogen peroxide (5 uM), ascorbate (0.1-0.3 mM), and sodium hydrosulfite (0.1 mM). Inhibited by high concentrations of hydrogen peroxide (0.1 mM), ascorbate (10 mM), and sodium hydrosulfite (1 mM). Optimum pH is 8.0. Optimum temperature is 40 degrees Celsius. Amino-acid degradation; L-tryptophan degradation via kynurenine pathway; L-kynurenine from L-tryptophan: step 1/2. Pigment biosynthesis; ommochrome biosynthesis. Homotetramer. Dimer of dimers. Belongs to the tryptophan 2,3-dioxygenase family.