Involved in the pathway of tryptophan degradation. Reduces FAD/FMN to FADH(2)/FMNH(2), which are subsequently used for the hydroxylation of anthranilate. It can reduce either FAD or flavin mononucleotide (FMN) but prefers FAD. The enzyme has a slight preference for NADPH as acceptor. FADH2 + NAD(+) = FAD + 2 H(+) + NADH FADH2 + NADP(+) = FAD + 2 H(+) + NADPH With FAD as substrate NADH can be used as an electron donor, with 95% activity relative to NADPH. Anthranilate 3-monooxygenase consists of a reductase component (GTNG_3158) and an oxygenase component HpaH.