Most, if not all enzymes in the kynurenine metabolic pathway have crystal structures available (check text for details of reaction steps). Selected links are provided below:
Human TDO2 – http://www.rcsb.org/pdb/explore/explore.do?structureId=4PW8
Human IDO1 – http://www.rcsb.org/pdb/explore/explore.do?structureId=4PK6
Human KATI with PLP – http://www.rcsb.org/pdb/explore/explore.do?structureId=4WLH
Human KAT II with PLP – http://www.rcsb.org/pdb/explore/explore.do?structureId=5EUN
Mouse Kat III with PLP – http://www.rcsb.org/pdb/explore/explore.do?structureId=3E2F
Mouse Kat IV – http://www.rcsb.org/pdb/explore/explore.do?structureId=3HLM
Yeast apoKMO – http://www.rcsb.org/pdb/explore/explore.do?structureId=4J33
Yeast holoKMO, with inhibitor – http://www.rcsb.org/pdb/explore/explore.do?structureId=4J36
Human KYNU – http://www.rcsb.org/pdb/explore/explore.do?structureId=2HZP
Human HAAO – http://www.rcsb.org/pdb/explore/explore.do?structureId=2QNK
Human ACMSD – http://www.rcsb.org/pdb/explore/explore.do?structureId=4OFC