The Heme Environment of Recombinant Human Indoleamine 2,3-Dioxygenase

Terentis, Andrew C.; Thomas, Shane R.; Takikawa, Osamu; Littlejohn, Tamantha K.; Truscott, Roger J.W.; Armstrong, Robert S.; Yeh, Syun Ru; Stocker, Roland

doi:10.1074/jbc.m200457200

Cited by 95 publications

(176 citation statements)

References 36 publications

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“…Our model for the Michaelis complex shows that the O1 atom is 2.6 Å from the N1 atom of L-Trp and therefore can act as the general base to extract the proton from the N1 atom (SI Fig. 11) (19). The N1 atom is hydrogen-bonded to His 55 in TDO.…”

Section: Resultsmentioning

confidence: 99%

“…4a), which may favor the Criegee rearrangement pathway (SI Fig. 11) (19). The Criegee pathway is also favored based on chemical, thermodynamic, and quantum mechanical considerations (3).…”

Section: Resultsmentioning

confidence: 99%

“…It has been established that TDO has an ordered catalytic cycle in which the protein first binds L-Trp to the ferrous form, and then binding of dioxygen is facilitated, and nucleophilic attack from the substrate C3 is initiated (3,13,19). In the model, the distal oxygen atom interacts with the L-Trp ammonium moiety and the backbone amide nitrogen of Gly 125 (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Molecular insights into substrate recognition and catalysis by tryptophan 2,3-dioxygenase

Forouhar

Anderson

Mowat

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

169

284

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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-Å 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 dioxygenbinding 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.cancer ͉ heme enzymes ͉ immunomodulation ͉ indoleamine 2,3-dioxygenase T ryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) catalyze the oxidative cleavage of the L-tryptophan (L-Trp) pyrrole ring, the first and rate-limiting step in L-Trp catabolism through the kynurenine pathway (1-3). In addition, IDO has been implicated in a diverse range of physiological and pathological conditions, including suppression of T cell proliferation, maternal tolerance to allogenic fetus, and immune escape of cancers (4-8), and is an attractive target for drug discovery against cancer and autoimmune and other diseases (2, 9-12).Despite catalyzing identical biochemical reactions (Fig. 1a), the sequence similarity between TDO and IDO is extremely low. An alignment of their sequences is only possible based on their structures, which suggests a sequence identity of 10% between them (Fig. 1b). In comparison, Xanthomonas campestris TDO shares 34% sequence identity with human TDO (Fig. 1b), demonstrating the remarkable evolutionary conservation of this enzyme. TDO is a homotetrameric enzyme and is highly specific for L-Trp and related derivatives such as 6-fluoro-Trp as the substrate. In comparison, IDO is monomeric, and shows activity toward a larger collection of substrates, including L-Trp, Dtryptophan (D-Trp), serotonin, and tryptamine (3), although the K m for D-Trp is Ϸ100-fold higher than that for L-Trp (13). The structure of human IDO in the catalytically inactive, ferric [Fe(III)]-heme state in complex with the 4-phenylimidazole inhibitor has recently been reported (14). Although this structure gave information about important active site residues, the inhibitor is coordinat...

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Section: Resultsmentioning

confidence: 99%

“…4a), which may favor the Criegee rearrangement pathway (SI Fig. 11) (19). The Criegee pathway is also favored based on chemical, thermodynamic, and quantum mechanical considerations (3).…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Molecular insights into substrate recognition and catalysis by tryptophan 2,3-dioxygenase

Forouhar

Anderson

Mowat

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

169

284

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“…IndoDO is also capable of peroxidase-like activity [8,13]. Indeed, IndoDO exists in an oxygenated form that is still active to degrade substrates.…”

Section: Discussionmentioning

confidence: 99%

“…The conditions under which one can measure IndoDo activity are quite complex. Indeed, as described in the original report [7], and confirmed in numerous others [12][13][14][15], the experimental procedure involves ascorbic acid, Methylene Blue and catalase. Methylene Blue permits the transfer of electrons from ascorbic acid to molecular oxygen, leading to the formation of the superoxide anion.…”

Section: Introductionmentioning

confidence: 99%

Molecular evidence that melatonin is enzymatically oxidized in a different manner than tryptophan: investigations with both indoleamine 2,3-dioxygenase and myeloperoxidase

Ferry

Ubeaud

Lambert³

et al. 2005

Biochemical Journal

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The catabolism of melatonin, whether naturally occurring or ingested, takes place via two pathways: ∼ 70 % can be accounted for by conjugation (sulpho-and glucurono-conjugation), and ∼ 30 % by oxidation. It is commonly thought that the interferoninduced enzyme indoleamine 2,3-dioxygenase (EC 1.13.11.42), which oxidizes tryptophan, is also responsible for the oxidation of 5-hydroxytryptamine (serotonin) and its derivative, melatonin. Using the recombinant enzyme expressed in Escherichia coli, we show in the present work that indoleamine 2,3-dioxygenase indeed cleaves tryptophan; however, under the same conditions, it is incapable of cleaving the two other indoleamines. By contrast, myeloperoxidase (EC 1.11.1.7) is capable of cleaving the indole moiety of melatonin. However, when using the peroxidase conditions of assay -with H 2 O 2 as co-substrate -indoleamine 2,3-dioxygenase is able to cleave melatonin into its main metabolite, a kynurenine derivative. The present work establishes that the oxidative metabolism of melatonin is due, in the presence of H 2 O 2 , to the activities of both myeloperoxidase and indoleamine 2,3-dioxygenase (with lower potency), since both enzymes have K m values for melatonin in the micromolar range. Under these conditions, several indolic compounds can be cleaved by both enzymes, such as tryptamine and 5-hydroxytryptamine. Furthermore, melatonin metabolism results in a kynurenine derivative, the pharmacological action of which remains to be studied, and could amplify the mechanisms of action of melatonin.

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Iron: Heme Proteins, Mono‐ & DioxygenasesBased in part on the article Iron: Heme Proteins, Mono‐ & Dioxygenases by Masanori Sono & John H. Dawson which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Wong

Bell

2005

Encyclopedia of Inorganic Chemistry

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Heme (iron protoporphyrin IX) proteins and enzymes play crucial roles in all living organisms. Iron is very tightly bound to the porphyrin and does not dissociate under physiological conditions. Indeed the heme group is almost like a separate element altogether. It is redox‐active, and heme proteins such as cytochrome c have important electron‐transfer functions. The strong π donor nature of heme iron(II) also means that heme proteins are involved in the binding and activation of small molecules such as oxygen. The P450 heme monooxygenases use two electrons and two protons to activate O 2 , giving one molecule of water and a high‐valent iron‐oxo intermediate that is sufficiently reactive to attack aliphatic CH bonds in a diverse range of organic molecules. The heme dioxygenases, as the name implies, insert both oxygen atoms of the O 2 molecule into the substrate. The known heme dioxygenases are indoleamine ring cleavage enzymes but have not been studied in detail, and no crystal structure of the enzymes is available. It is known that the active form of the enzyme has Fe(II), and that both oxygen and superoxide could be the source of the two oxygen atoms inserted into substrates. The main focus of this article is on the cytochrome P450 monooxygenases. The P450 (CYP) superfamily of enzymes is found in virtually all organisms where they catalyze the oxidation of endogenous and exogenous organic compounds. These reactions are vital steps in the biosynthesis of steroids and other hormones, and the detoxification and oxidative removal of xenobiotics. The primary activity of P450 enzymes is CH bond oxidation, but other activities such as alkene epoxidation, CC bond cleavage, heteroatom oxidation, and even reductive reactions are known. These reactions and their mechanisms are surveyed. The major sections review and summarize the steps in the P450 catalytic cycle, the nature of the rate‐limiting step, the chemical properties and electronic structure of the heme in the intermediates, and the mechanism of CH bond oxidation. The unique activity of P450 enzymes does not arise solely from the heme group; the pivotal roles of the protein environment and dynamics are discussed. The mechanism of aliphatic CH bond oxidation is one of the great challenges in chemistry. The nature of the active intermediate in P450 catalysis and the mechanism of action remain controversial. The results of mechanistic and theoretical approaches are brought together and reviewed.

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The Heme Environment of Recombinant Human Indoleamine 2,3-Dioxygenase

Cited by 95 publications

References 36 publications

Molecular insights into substrate recognition and catalysis by tryptophan 2,3-dioxygenase

Molecular insights into substrate recognition and catalysis by tryptophan 2,3-dioxygenase

Molecular evidence that melatonin is enzymatically oxidized in a different manner than tryptophan: investigations with both indoleamine 2,3-dioxygenase and myeloperoxidase

Iron: Heme Proteins, Mono‐ & DioxygenasesBased in part on the article Iron: Heme Proteins, Mono‐ & Dioxygenases by Masanori Sono & John H. Dawson which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

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