Indoleamine 2,3-dioxygenase; part of the gene cluster that mediates the biosynthesis of terreazepine, (PubMed:32843555). The first step of terreazepine biosynthesis is catalyzed by the indoleamine 2,3-dioxygenase tpzB which produces N-formyl-kynurenine through the catabolism of tryptophan (PubMed:32843555). The two-module NRPS tpzA then utilizes anthranilate and kynurenine to assemble terreazepine (PubMed:32843555). The first adenylation domain of tpzA (A1) loads anthranilate onto the T1 domain, while A2 loads kynurenine, generated through spontaneous nonenzymatic deformylation of the tzpB-supplied N-formyl-kynurenine (PubMed:32843555). TpzA produces a 2:1 mixture of S-R enantiomers, which suggests that the A2 domain accepts both D- and L-kynurenine (PubMed:32843555). The peptide bond formation between the tethered amino acids is catalyzed by the first condensation domain (C1) between anthranilate's carbonyl carbon and kynurenine's aliphatic primary amine (PubMed:32843555). The second C domain (C2) catalyzes the final cyclization event between the aromatic amine of kynurenine and the tethered carbonyl carbon, yielding the final terreazepine product (PubMed:32843555). The T3 domain may facilitate the interaction with downstream tailoring enzymes (PubMed:32843555). D-tryptophan + O2 = N-formyl-D-kynurenine L-tryptophan + O2 = N-formyl-L-kynurenine Binds 1 heme group per subunit. Secondary metabolite biosynthesis. Belongs to the indoleamine 2,3-dioxygenase family.