Molecular Insights into Substrate Recognition and Catalysis by Tryptophan 2,3-dioxygenase

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Proceedings of the National Academy of Sciences of the USA

DOI:https://doi.org/10.1073/pnas.0610007104· OSTI ID:930298

Forouhar, F; Ross Anderson, J; Mowat, C; Vorobiev, S; Hussain, A; Abashidze, M; Bruckmann, C; Thackray, S; Seetharaman, J

Tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) constitute an important, yet relatively poorly understood, family of heme-containing enzymes. Here, we report extensive structural and biochemical studies of the Xanthomonas campestris TDO and a related protein SO4414 from Shewanella oneidensis, including the structure at 1.6-{angstrom} resolution of the catalytically active, ferrous form of TDO in a binary complex with the substrate l-Trp. The carboxylate and ammonium moieties of tryptophan are recognized by electrostatic and hydrogen-bonding interactions with the enzyme and a propionate group of the heme, thus defining the l-stereospecificity. A second, possibly allosteric, l-Trp-binding site is present at the tetramer interface. The sixth coordination site of the heme-iron is vacant, providing a dioxygen-binding site that would also involve interactions with the ammonium moiety of l-Trp and the amide nitrogen of a glycine residue. The indole ring is positioned correctly for oxygenation at the C2 and C3 atoms. The active site is fully formed only in the binary complex, and biochemical experiments confirm this induced-fit behavior of the enzyme. The active site is completely devoid of water during catalysis, which is supported by our electrochemical studies showing significant stabilization of the enzyme upon substrate binding.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 930298
• Report Number(s): BNL--81003-2008-JA
• Journal Information: Proceedings of the National Academy of Sciences of the USA, Journal Name: Proceedings of the National Academy of Sciences of the USA Journal Issue: 2 Vol. 104
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
AMIDES
ATOMS
CATALYSIS
ELECTROSTATICS
ENZYMES
GLYCINE
HEME
INDOLES
INTERACTIONS
NITROGEN
PROTEINS
RESOLUTION
RINGS
STABILIZATION
SUBSTRATES
TRYPTOPHAN
WATER
national synchrotron light source