A Kinetic, Spectroscopic, and Redox Study of Human Tryptophan 2,3-Dioxygenase

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

doi:10.1021/bi702393b

Cited by 64 publications

(106 citation statements)

References 20 publications

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“…In our previous study of ferrous TDO, the CO adduct exhibits a Soret band at 421 nm in the presence of L-Trp, and it is stable in the presence of O 2 (24). A similar 421-nm peak has also been reported for the ferrous-CO adduct of human TDO (41). When CO was bubbled into a solution containing ferric TDO and L-Trp, the addition of CO does not cause an observable shift of the Soret band.…”

Section: Reaction Of Oxidized Tdo and H 2 O 2 With L-trp-supporting

confidence: 66%

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Enzyme Reactivation by Hydrogen Peroxide in Heme-based Tryptophan Dioxygenase

Gupta

Geng

et al. 2011

Journal of Biological Chemistry

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An intriguing mystery about tryptophan 2,3-dioxygenase is its hydrogen peroxide-triggered enzyme reactivation from the resting ferric oxidation state to the catalytically active ferrous form. In this study, we found that such an odd Fe(III) reduction by an oxidant depends on the presence of L-Trp, which ultimately serves as the reductant for the enzyme. In the peroxide reaction with tryptophan 2,3-dioxygenase, a previously unknown catalase-like activity was detected. A ferryl species (␦ ‫؍‬ 0.055 mm/s and ⌬E Q ‫؍‬ 1.755 mm/s) and a protein-based free radical (g ‫؍‬ 2.0028 and 1.72 millitesla linewidth) were characterized by Mössbauer and EPR spectroscopy, respectively. This is the first compound ES-type of ferryl intermediate from a heme-based dioxygenase characterized by EPR and Mössbauer spectroscopy. Density functional theory calculations revealed the contribution of secondary ligand sphere to the spectroscopic properties of the ferryl species. In the presence of L-Trp, the reactivation was demonstrated by enzyme assays and by various spectroscopic techniques. A Trp-Trp dimer and a monooxygenated L-Trp were both observed as the enzyme reactivation byproducts by mass spectrometry. Together, these results lead to the unraveling of an over 60-year old mystery of peroxide reactivation mechanism. These results may shed light on how a metalloenzyme maintains its catalytic activity in an oxidizing environment.Hemoproteins perform a wide range of biological functions, including oxygen transport, storage, electron transfer, monooxygenation, and reduction of dioxygen. However, they rarely express dioxygenase activity as their native biological function. Tryptophan 2,3-dioxygenase (TDO) 3 is the first described exception (1-3). This enzyme employs a b-type ferrous heme prosthetic group to catalyze the oxidative cleavage of the indole ring of L-Trp, converting it to N-formylkynurenine (NFK) (Scheme 1). This is the first and rate-limiting step of the kynurenine pathway of L-Trp metabolism, which oxidizes over 99% of L-Trp in mammalian intracellular and extracellular pools (2, 4 -9). The kynurenine pathway constitutes the major steps in biosynthesis of NAD, an essential redox cofactor in all living systems (5).TDO is a hepatic enzyme first discovered in rat liver extracts in 1936 (1). An analogous enzyme, indoleamine 2,3-dioxygenase (IDO), was isolated 31 years later from tissues other than the liver (10). Although both enzymes catalyze the same reaction, TDO is highly substrate-specific with L-Trp, whereas IDO presents a more relaxed specificity. TDO is a homotetramer with a total mass of ϳ134 kDa, whereas IDO is a monomeric protein. The two enzymes share only 14% sequence identity but conserve similar active site architectures (11-13). In addition to humans, TDO has also been found in other mammals, such as rats and mice, as well as in mosquitoes and bacteria (2, 5, 14 -18). Recently, a potential heme-dependent dioxygenase enzyme superfamily has been proposed (19). Moreover, several other heme-based proteins, such as my...

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Section: Reaction Of Oxidized Tdo and H 2 O 2 With L-trp-supporting

confidence: 66%

“…It is known that CO reacts with the ferrous heme of TDO and that the ferrous-CO complex is catalytically inactive (41). Like O 2 , CO does not bind to ferric hemoproteins (42).…”

Section: Reaction Of Oxidized Tdo and H 2 O 2 With L-trp-mentioning

confidence: 99%

Enzyme Reactivation by Hydrogen Peroxide in Heme-based Tryptophan Dioxygenase

Gupta

Geng

et al. 2011

Journal of Biological Chemistry

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“…34,48−50 All of the cmTDO mutants showed the same trend of change in spintransition upon substrate binding ( Figure 1B−1D). By comparing its g-values with those of the hydroxide-bound ferric low-spin species identified in other hemoproteins, 45,51 this newly produced low-spin species can be assigned as such. It has been proposed that the hydroxide ligand is derived from an active site water, 26,36,46 which has been shown to be H-bonded to the amine group of the substrate in the ligand-bound crystal structure of xcTDO.…”

Section: ■ Resultsmentioning

confidence: 99%

Chemical Rescue of the Distal Histidine Mutants of Tryptophan 2,3-Dioxygenase

2012

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Tryptophan 2,3-dioxygenase (TDO) is a heme-dependent enzyme that catalyzes the oxidative degradation of L-tryptophan (L-Trp) to N-formylkynurenine (NFK). A highly conserved histidine residue in the distal heme pocket has attracted great attention in the mechanistic studies of TDO. However, a consensus has not been reached regarding whether and how this distal histidine plays a catalytic role after substrate binding. In this study, three mutant proteins, H72S, H72N, and Q73F were generated to investigate the function of the distal histidine residue in Cupriavidus metallidurans TDO (cmTDO). Spectroscopic characterizations, enzymatic kinetic analysis, and chemical rescue assays were employed to study the biochemical properties of the wild-type enzyme and the mutant proteins. Rapid kinetic methods were utilized to explore the molecular basis for the observed stimulation of catalytic activity by 2-methylimidazole in the His72 variants. The results indicate that the distal histidine plays multiple roles in cmTDO. First, His72 contributes to but is not essential for substrate binding. In addition, it shields the heme center from nonproductive binding of exogenous small ligand molecules (i.e., imidazole and its analogs) via steric hindrance. Most importantly, His72 participates in the subsequent chemical catalytic steps after substrate binding possibly by providing H-bonding interactions to the heme-bound oxygen.

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“…these enzymes catalyze the same dioxygenase reaction and contain similar heme active sites (8 -10), IDO and TDO are distinct enzymes that are monomeric and homotetrameric, respectively, share only 10% sequence identity (9), and show differences in tissue distribution, protein structure, substrate specificity and binding, and enzyme reactivity (11)(12)(13).…”

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confidence: 99%

Human Indoleamine 2,3-Dioxygenase Is a Catalyst of Physiological Heme Peroxidase Reactions

Freewan

Rees

Plaza

et al. 2013

Journal of Biological Chemistry

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Background: Certain heme proteins exhibit a pseudo-peroxidase activity that alters their function. Results: H 2 O 2 engages the peroxidase activity of indoleamine 2,3-dioxygenase (IDO) to oxidatively inactivate its dioxygenase activity, consume nitric oxide, and promote IDO protein nitration. Conclusion: IDO is a catalyst of physiological peroxidase reactions. Significance: IDO peroxidase activity has novel implications for the control and biological actions of this important immune regulatory enzyme.

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A Kinetic, Spectroscopic, and Redox Study of Human Tryptophan 2,3-Dioxygenase

Cited by 64 publications

References 20 publications

Enzyme Reactivation by Hydrogen Peroxide in Heme-based Tryptophan Dioxygenase

Enzyme Reactivation by Hydrogen Peroxide in Heme-based Tryptophan Dioxygenase

Chemical Rescue of the Distal Histidine Mutants of Tryptophan 2,3-Dioxygenase

Human Indoleamine 2,3-Dioxygenase Is a Catalyst of Physiological Heme Peroxidase Reactions

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