TDO (Anopheles gambiae) (rec.) (His)

Tryptophan 2,3-dioxygenase (TDO) is a heme-containing dioxygenase catalyzing the addition of molecular oxygen across the 2,3-double bond of the indole ring of tryptophan to form N-formylkynurenine (NFK). In Anopheles gambiae, TDO is the only enzyme able to catalyze the first and rate-limiting step in L-Trp catabolism through the kynurenine pathway. Tryptophan is an essential amino acid for protein synthesis and also the precursor for production of a number of neurotransmitters, such as serotonin and melatonin; in mosquitoes, the kynurenine pathway is essential for eye pigmentation. Conceivably, the tryptophan-using pathways should be regulated in a coordinated manner in mosquitoes as well as in other species and TDO activation/inactivation processes could play an essential role in these phenomena.