A kinetic, spectroscopic, and redox study of human tryptophan 2,3-dioxygenase.
The family of heme dioxygenases, as exemplified by indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase, catalyzes the oxidative cleavage of L-tryptophan to N-formylkynurenine. Here, we describe a bacterial expression system for human tryptophan 2,3-dioxygenase (rhTDO) together with spectroscopic, kinetic, and redox analyses. We find unexpected differences between human tryptophan 2,3-dioxygenase and human indoleamine 2,3-dioxygenase [Chauhan et al. (2008) Biochemistry 47, 4761-4769 ]. Thus, in contrast to indoleamine 2,3-dioxygenase, the catalytic ferrous-oxy complex of rhTDO is not observed, nor does the enzyme discriminate against substrate binding to the ferric derivative. In addition, we show that the rhTDO is also catalytically active in the ferric form. These new findings illustrate that significant mechanistic differences exist across the heme dioxygenase family, and the data are discussed within this broader framework.
Basran
Jaswir
J
Department of Biochemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester, England.
Rafice
Sara A
SA
Chauhan
Nishma
N
Efimov
Igor
I
Cheesman
Myles R
MR
Ghamsari
Lila
L
Raven
Emma Lloyd
EL
D004583:Electrons; D015870:Gene Expression; D006801:Humans; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011199:Potentiometry; D011485:Protein Binding; D013053:Spectrophotometry; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism; D014366:Tryptophan Oxygenase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D008024:Ligands; D014364:Tryptophan; D007501:Iron; D014366:Tryptophan Oxygenase; D010100:Oxygen