Tryptophan-2,3-dioxygenase (TDO)

Tryptophan 2,3-dioxygenase (EC 1.13.11.11) plays a role in catalyzing the first and rat-limiting step in the kynurenine pathway, the major pathway of tryptophan metabolism.

Compared to the rat, the regulatory region of the human TDO2 gene had an insertion of approximately 1,064 bp of random DNA beginning at -293 bp and extended to -1357 bp. This displaced the glucocorticoid response element (GRE) occurring at -1174 bp in the rat to -1500 in human. The proximal GRE at -419 in the rat was missing in the human. However, within the DNA insert there was a GRE-like microsatellite region containing multiple GTT repeats plus additional GT(n) sequences. The intronic regions 5-prime and 3-prime to each exon were sequenced.