A kinetic, spectroscopic, and redox study of human tryptophan 2,3-dioxygenase

Jaswir Basran, Sara A. Rafice, Nishma Chauhan, Igor Efimov, Myles R. Cheesman, Lila Ghamsari, Emma Lloyd Raven

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60 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)4752-4760
Number of pages9
Issue number16
Publication statusPublished - 1 Apr 2008

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