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Louka S, Barry SM, Heyes DJ, Mubarak MQE, Ali HS, Alkhalaf LM, Munro AW, Scrutton NS, Challis GL, de Visser SP. Catalytic Mechanism of Aromatic Nitration by Cytochrome P450 TxtE: Involvement of a Ferric-Peroxynitrite Intermediate. J Am Chem Soc 2020; 142:15764-15779. [PMID: 32811149 PMCID: PMC7586343 DOI: 10.1021/jacs.0c05070] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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The
cytochromes P450 are heme-dependent enzymes that catalyze many
vital reaction processes in the human body related to biodegradation
and biosynthesis. They typically act as mono-oxygenases; however,
the recently discovered P450 subfamily TxtE utilizes O2 and NO to nitrate aromatic substrates such as L-tryptophan.
A direct and selective aromatic nitration reaction may be useful in
biotechnology for the synthesis of drugs or small molecules. Details
of the catalytic mechanism are unknown, and it has been suggested
that the reaction should proceed through either an iron(III)-superoxo
or an iron(II)-nitrosyl intermediate. To resolve this controversy,
we used stopped-flow kinetics to provide evidence for a catalytic
cycle where dioxygen binds prior to NO to generate an active iron(III)-peroxynitrite
species that is able to nitrate l-Trp efficiently. We show
that the rate of binding of O2 is faster than that of NO
and also leads to l-Trp nitration, while little evidence
of product formation is observed from the iron(II)-nitrosyl complex.
To support the experimental studies, we performed density functional
theory studies on large active site cluster models. The studies suggest
a mechanism involving an iron(III)-peroxynitrite that splits homolytically
to form an iron(IV)-oxo heme (Compound II) and a free NO2 radical via a small free energy of activation. The latter activates
the substrate on the aromatic ring, while compound II picks up the ipso-hydrogen to form the product. The calculations give
small reaction barriers for most steps in the catalytic cycle and,
therefore, predict fast product formation from the iron(III)-peroxynitrite
complex. These findings provide the first detailed insight into the
mechanism of nitration by a member of the TxtE subfamily and highlight
how the enzyme facilitates this novel reaction chemistry.
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Affiliation(s)
- Savvas Louka
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Mancheste M13 9PL, United Kingdom
| | - Sarah M Barry
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Derren J Heyes
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - M Qadri E Mubarak
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Mancheste M13 9PL, United Kingdom
| | - Hafiz Saqib Ali
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Lona M Alkhalaf
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Andrew W Munro
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Nigel S Scrutton
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Gregory L Challis
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom.,Department of Biochemistry and Molecular Biology, Monash University, Clayton VIC 3800, Australia.,ARC Centre for Excellence for Innovations in Peptide and Protein Science, Monash University, Clayton, VIC 3800, Australia
| | - Sam P de Visser
- The Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.,Department of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Mancheste M13 9PL, United Kingdom
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2
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Su Z, Horner JH, Newcomb M. Cytochrome P450 119 Compounds I Formed by Chemical Oxidation and Photooxidation Are the Same Species. Chemistry 2019; 25:14015-14020. [PMID: 23108625 PMCID: PMC3930626 DOI: 10.1002/chem.201202254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Indexed: 11/07/2022]
Abstract
Compound I from cytochrome P450 119 prepared by the photooxidation method involving peroxynitrite oxidation of the resting enzyme to Compound II followed by photooxidation to Compound I was compared to Compound I generated by m-chloroperoxybenzoic acid (MCPBA) oxidation of the resting enzyme. The two methods gave the same UV/Visible spectra, the same products from oxidations of lauric acid and palmitic acid and their (ω-2,ω-2,ω-3,ω-3)-tetradeuterated analogues, and the same kinetics for oxidations of lauric acid and caprylic acid. The experimental identities between the transients produced by the two methods leave no doubt that the same Compound I species is formed by the two methods.
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Affiliation(s)
- Zhi Su
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60617 U.S.A, Fax: (+1) 312-996-0431
| | - John H. Horner
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60617 U.S.A, Fax: (+1) 312-996-0431
| | - Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60617 U.S.A, Fax: (+1) 312-996-0431
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3
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Caranto JD. The emergence of nitric oxide in the biosynthesis of bacterial natural products. Curr Opin Chem Biol 2019; 49:130-138. [DOI: 10.1016/j.cbpa.2018.11.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/28/2018] [Accepted: 11/09/2018] [Indexed: 12/16/2022]
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4
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Lang J, Maréchal A, Couture M, Santolini J. Reaction Intermediates and Molecular Mechanism of Peroxynitrite Activation by NO Synthases. Biophys J 2017; 111:2099-2109. [PMID: 27851935 DOI: 10.1016/j.bpj.2016.05.056] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 05/26/2016] [Accepted: 05/31/2016] [Indexed: 11/26/2022] Open
Abstract
The activation of the peroxynitrite anion (PN) by hemoproteins, which leads to its detoxification or, on the contrary to the enhancement of its cytotoxic activity, is a reaction of physiological importance that is still poorly understood. It has been known for some years that the reaction of hemoproteins, notably cytochrome P450, with PN leads to the buildup of an intermediate species with a Soret band at ∼435 nm (I435). The nature of this intermediate is, however, debated. On the one hand, I435 has been presented as a compound II species that can be photoactivated to compound I. A competing alternative involves the assignment of I435 to a ferric-nitrosyl species. Similar to cytochromes P450, the buildup of I435 occurs in nitric oxide synthases (NOSs) upon their reaction with excess PN. Interestingly, the NOS isoforms vary in their capacity to detoxify/activate PN, although they all show the buildup of I435. To better understand PN activation/detoxification by heme proteins, a definitive assignment of I435 is needed. Here we used a combination of fine kinetic analysis under specific conditions (pH, PN concentrations, and PN/NOSs ratios) to probe the formation of I435. These studies revealed that I435 is not formed upon homolytic cleavage of the O-O bond of PN, but instead arises from side reactions associated with excess PN. Characterization of I435 by resonance Raman spectroscopy allowed its identification as a ferric iron-nitrosyl complex. Our study indicates that the model used so far to depict PN interactions with hemo-thiolate proteins, i.e., leading to the formation and accumulation of compound II, needs to be reconsidered.
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Affiliation(s)
- Jérôme Lang
- Laboratory of Oxidative Stress and Detoxification, iBiTec-S/I2BC, UMR 9198, CEA-Centre National de la Recherche Scientifique Université Paris Sud, CEA Saclay, Gif-sur-Yvette Cedex, France; Department of Biochemistry, Université Laval, Laval, Québec, Canada
| | - Amandine Maréchal
- Laboratory of Oxidative Stress and Detoxification, iBiTec-S/I2BC, UMR 9198, CEA-Centre National de la Recherche Scientifique Université Paris Sud, CEA Saclay, Gif-sur-Yvette Cedex, France
| | - Manon Couture
- Department of Biochemistry, Université Laval, Laval, Québec, Canada
| | - Jérôme Santolini
- Laboratory of Oxidative Stress and Detoxification, iBiTec-S/I2BC, UMR 9198, CEA-Centre National de la Recherche Scientifique Université Paris Sud, CEA Saclay, Gif-sur-Yvette Cedex, France.
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5
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Krest CM, Onderko EL, Yosca TH, Calixto JC, Karp RF, Livada J, Rittle J, Green MT. Reactive intermediates in cytochrome p450 catalysis. J Biol Chem 2013; 288:17074-81. [PMID: 23632017 DOI: 10.1074/jbc.r113.473108] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, we reported the spectroscopic and kinetic characterizations of cytochrome P450 compound I in CYP119A1, effectively closing the catalytic cycle of cytochrome P450-mediated hydroxylations. In this minireview, we focus on the developments that made this breakthrough possible. We examine the importance of enzyme purification in the quest for reactive intermediates and report the preparation of compound I in a second P450 (P450ST). In an effort to bring clarity to the field, we also examine the validity of controversial reports claiming the production of P450 compound I through the use of peroxynitrite and laser flash photolysis.
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Affiliation(s)
- Courtney M Krest
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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6
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Abstract
P450(BM3) (CYP102A1), a fatty acid hydroxylase from Bacillus megaterium, has been extensively studied over a period of almost forty years. The enzyme has been redesigned to catalyse the oxidation of non-natural substrates as diverse as pharmaceuticals, terpenes and gaseous alkanes using a variety of engineering strategies. Crystal structures have provided a basis for several of the catalytic effects brought about by mutagenesis, while changes to reduction potentials, inter-domain electron transfer rates and catalytic parameters have yielded functional insights. Areas of active research interest include drug metabolite production, the development of process-scale techniques, unravelling general mechanistic aspects of P450 chemistry, methane oxidation, and improving selectivity control to allow the synthesis of fine chemicals. This review draws together the disparate research themes and places them in a historical context with the aim of creating a resource that can be used as a gateway to the field.
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Affiliation(s)
- Christopher J C Whitehouse
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
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7
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Chen X, Su Z, Horner JH, Newcomb M. Oxidation of 10-undecenoic acid by cytochrome P450(BM-3) and its Compound I transient. Org Biomol Chem 2011; 9:7427-33. [PMID: 21901220 DOI: 10.1039/c1ob06035j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxidations of 10-undecenoic acid by cytochrome P450(BM-3) and its Compound I transient were studied. The only product formed in Compound I oxidations was 10,11-epoxyundecanoic acid, whereas the enzyme under turnover conditions gave the epoxide and 9-hydroxy-10-undecenoic acid in a 10 : 90 ratio. Kinetic studies at 0 °C of oxidations by Compounds I formed by MCPBA oxidation and by a photo-oxidation pathway gave the same results, displaying saturation kinetics that yielded equilibrium binding constants and first-order oxidation rate constants that were experimentally indistinguishable. Oxidation of 10-undecenoic acid by Compound I from CYP119 generated by MCBPA oxidation also gave 10,11-epoxyundecanoic acid as the only product. CYP119 Compound I bound the substrate less strongly but reacted with a faster oxidation rate constant than P450(BM-3) Compound I. The kinetic parameters for oxidation of the substrate by P450(BM-3) under turnover conditions were similar to those of the Compound I transient even though the products differed.
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Affiliation(s)
- Xiaohong Chen
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60607, USA.
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8
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Sivaramakrishnan S, Ouellet H, Du J, McLean KJ, Medzihradszky KF, Dawson JH, Munro AW, Ortiz de Montellano PR. A novel intermediate in the reaction of seleno CYP119 with m-chloroperbenzoic acid. Biochemistry 2011; 50:3014-24. [PMID: 21381758 DOI: 10.1021/bi101728y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochrome P450-mediated monooxygenation generally proceeds via a reactive ferryl intermediate coupled to a ligand radical [Fe(IV)═O]+• termed Compound I (Cpd I). The proximal cysteine thiolate ligand is a critical determinant of the spectral and catalytic properties of P450 enzymes. To explore the effect of an increased level of donation of electrons by the proximal ligand in the P450 catalytic cycle, we recently reported successful incorporation of SeCys into the active site of CYP119, a thermophilic cytochrome P450. Here we report relevant physical properties of SeCYP119 and a detailed analysis of the reaction of SeCYP119 with m-chloroperbenzoic acid. Our results indicate that the selenolate anion reduces rather than stabilizes Cpd I and also protects the heme from oxidative destruction, leading to the generation of a new stable species with an absorbance maximum at 406 nm. This stable intermediate can be returned to the normal ferric state by reducing agents and thiols, in agreement with oxidative modification of the selenolate ligand itself. Thus, in the seleno protein, the oxidative damage shifts from the heme to the proximal ligand, presumably because (a) an increased level of donation of electrons more efficiently quenches reactive species such as Cpd I and (b) the protection of the thiolate ligand provided by the protein active site structure is insufficient to shield the more oxidizable selenolate ligand.
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Affiliation(s)
- Santhosh Sivaramakrishnan
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517, United States
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9
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Cooper HLR, Groves JT. Molecular probes of the mechanism of cytochrome P450. Oxygen traps a substrate radical intermediate. Arch Biochem Biophys 2011; 507:111-8. [PMID: 21075070 PMCID: PMC3041850 DOI: 10.1016/j.abb.2010.11.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 11/05/2010] [Accepted: 11/05/2010] [Indexed: 01/05/2023]
Abstract
The diagnostic substrate tetramethylcyclopropane (TMCP) has been reexamined as a substrate with three drug- and xenobiotic-metabolizing cytochrome P450 enzymes, human CYP2E1, CYP3A4 and rat CYP2B1. The major hydroxylation product in all cases was the unrearranged primary alcohol along with smaller amounts of a rearranged tertiary alcohol. Significantly, another ring-opened product, diacetone alcohol, was also observed. With CYP2E1 this product accounted for 20% of the total turnover. Diacetone alcohol also was detected as a product from TMCP with a biomimetic model catalyst, FeTMPyP, but not with a ruthenium porphyrin catalyst. Lifetimes of the intermediate radicals were determined from the ratios of rearranged and unrearranged products to be 120, 13 and 1ps for CYP2E1, CYP3A4 and CYP2B1, respectively, corresponding to rebound rates of 0.9×10(10)s(-1), 7.2×10(10)s(-1) and 1.0×10(12)s(-1). For the model iron porphyrin, FeTMPyP, a radical lifetime of 81ps and a rebound rate of 1.2×10(10)s(-1) were determined. These apparent radical lifetimes are consistent with earlier reports with a variety of CYP enzymes and radical clock substrates, however, the large amounts of diacetone alcohol with CYP2E1 and the iron porphyrin suggest that for these systems a considerable amount of the intermediate carbon radical is trapped by molecular oxygen. These results add to the view that cage escape of the intermediate carbon radical in [Fe(IV)-OH ()R] can compete with cage collapse to form a C-O bond. The results could be significant with regard to our understanding of iron-catalyzed C-H hydroxylation, the observation of P450-dependent peroxidation and the development of oxidative stress, especially for CYP2E1.
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Affiliation(s)
| | - John T. Groves
- Department of Chemistry, Princeton University, Princeton NJ 08544 USA
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10
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Jung C. The mystery of cytochrome P450 Compound I. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:46-57. [DOI: 10.1016/j.bbapap.2010.06.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 05/31/2010] [Accepted: 06/04/2010] [Indexed: 10/19/2022]
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11
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Rittle J, Green MT. Cytochrome P450 compound I: capture, characterization, and C-H bond activation kinetics. Science 2010; 330:933-7. [PMID: 21071661 DOI: 10.1126/science.1193478] [Citation(s) in RCA: 991] [Impact Index Per Article: 70.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Cytochrome P450 enzymes are responsible for the phase I metabolism of approximately 75% of known pharmaceuticals. P450s perform this and other important biological functions through the controlled activation of C-H bonds. Here, we report the spectroscopic and kinetic characterization of the long-sought principal intermediate involved in this process, P450 compound I (P450-I), which we prepared in approximately 75% yield by reacting ferric CYP119 with m-chloroperbenzoic acid. The Mössbauer spectrum of CYP119-I is similar to that of chloroperoxidase compound I, although its electron paramagnetic resonance spectrum reflects an increase in |J|/D, the ratio of the exchange coupling to the zero-field splitting. CYP119-I hydroxylates the unactivated C-H bonds of lauric acid [D(C-H) ~ 100 kilocalories per mole], with an apparent second-order rate constant of k(app) = 1.1 × 10(7) per molar per second at 4°C. Direct measurements put a lower limit of k ≥ 210 per second on the rate constant for bound substrate oxidation, whereas analyses involving kinetic isotope effects predict a value in excess of 1400 per second.
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Affiliation(s)
- Jonathan Rittle
- Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA
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12
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Schopfer MP, Wang J, Karlin KD. Bioinspired heme, heme/nonheme diiron, heme/copper, and inorganic NOx chemistry: *NO((g)) oxidation, peroxynitrite-metal chemistry, and *NO((g)) reductive coupling. Inorg Chem 2010; 49:6267-82. [PMID: 20666386 DOI: 10.1021/ic100033y] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The focus of this Forum Article highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide [nitrogen monoxide, *NO((g))] and its biological roles and reactions. The latter focus is on (i) oxidation of *NO((g)) to nitrate by nitric oxide dioxygenases (NODs) and (ii) reductive coupling of two molecules of *NO((g)) to give N(2)O(g). In the former case, NODs are described, and the highlighting of possible peroxynitrite/heme intermediates and the consequences of this are given by a discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with *NO((g)) and O(2)(g), leading to peroxynitrite species, are given. The coverage of biological reductive coupling of *NO((g)) deals with bacterial nitric oxide reductases (NORs) with heme/nonheme diiron active sites and on heme/copper oxidases such as cytochrome c oxidase, which can mediate the same chemistry. Recently designed protein and synthetic model compounds (heme/nonheme/diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, that describe the oxidation of *NO((g)) to nitrate (or nitrite) and possible peroxynitrite intermediates or reductive coupling of *NO((g)) to give nitrous oxide.
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Affiliation(s)
- Mark P Schopfer
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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13
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Abstract
Oxygenated heme proteins are known to react rapidly with nitric oxide (NO) to produce peroxynitrite (PN) at the heme site. This process could lead either to attenuation of the effects of NO or to nitrosative protein damage. PN is a powerful nitrating and oxidizing agent that has been implicated in a variety of cell injuries. Accordingly, it is important to delineate the nature and variety of reaction mechanisms of PN interactions with heme proteins. In this Forum, we survey the range of reactions of PN with heme proteins, with particular attention to myoglobin and cytochrome c. While these two proteins are textbook paradigms for oxygen binding and electron transfer, respectively, both have recently been shown to have other important functions that involve NO and PN. We have recently described direct evidence that ferrylmyolgobin (ferrylMb) and nitrogen dioxide (NO(2)) are both produced during the reaction of PN and metmyolgobin (metMb) (Su, J.; Groves, J. T. J. Am. Chem. Soc. 2009, 131, 12979-12988). Kinetic evidence indicates that these products evolve from the initial formation of a caged radical intermediate [Fe(IV) horizontal lineO.NO(2)]. This caged pair reacts mainly via internal return with a rate constant k(r) to form metMb and nitrate in an oxygen-rebound scenario. Detectable amounts of ferrylMb are observed by stopped-flow spectrophotometry, appearing at a rate consistent with the rate, k(obs), of heme-mediated PN decomposition. Freely diffusing NO(2), which is liberated concomitantly from the radical pair (k(e)), preferentially nitrates myoglobin Tyr103 and added fluorescein. For cytochrome c, Raman spectroscopy has revealed that a substantial fraction of cytochrome c converts to a beta-sheet structure, at the expense of turns and helices at low pH (Balakrishnan, G.; Hu, Y.; Oyerinde, O. F.; Su, J.; Groves, J. T.; Spiro, T. G. J. Am. Chem. Soc., 2007, 129, 504-505). It is proposed that a short beta-sheet segment, comprising residues 37-39 and 58-61, extends itself into the large 37-61 loop when the latter is destabilized by protonation of H26, which forms an anchoring hydrogen bond to loop residue P44. This conformation change ruptures the Met80-Fe bond, as revealed by changes in ligation-sensitive Raman bands. It also induces peroxidase activity with the same temperature profile. This process is suggested to model the apoptotic peroxidation of cardiolipin by cytochrome c.
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Affiliation(s)
- Jia Su
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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14
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Maréchal A, Mattioli TA, Stuehr DJ, Santolini J. NO synthase isoforms specifically modify peroxynitrite reactivity. FEBS J 2010; 277:3963-73. [DOI: 10.1111/j.1742-4658.2010.07786.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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15
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Rittle J, Younker JM, Green MT. Cytochrome P450: The Active Oxidant and Its Spectrum. Inorg Chem 2010; 49:3610-7. [DOI: 10.1021/ic902062d] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jonathan Rittle
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Jarod M. Younker
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Michael T. Green
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
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16
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Affiliation(s)
- Paul R. Ortiz de Montellano
- Department of Pharmaceutical Chemistry, University of California, 600 16 Street, San Francisco, California 94158-2517
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17
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Su J, Groves JT. Direct detection of the oxygen rebound intermediates, ferryl Mb and NO2, in the reaction of metmyoglobin with peroxynitrite. J Am Chem Soc 2010; 131:12979-88. [PMID: 19705829 DOI: 10.1021/ja902473r] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxygenated hemoproteins are known to react rapidly with nitric oxide (NO) to produce peroxynitrite (PN) at the heme site. This process could lead either to attenuation of the effects of NO or to nitrosative protein damage. Peroxynitrite is a powerful nitrating and oxidizing agent that has been implicated in a variety of cell injuries. Accordingly, it is important to delineate the nature and variety of reaction mechanisms of PN reactions with heme proteins. Here, we present direct evidence that ferrylMb and NO(2) are both produced during the reaction of PN and metmyoglobin (metMb). Kinetic evidence indicates that these products evolve from initial formation of a caged radical intermediate [Fe(IV)=O *NO(2)]. This caged pair reacts mainly via internal return with a rate constant k(r) to form metMb and nitrate in an oxygen rebound scenario. Detectable amounts of ferrylMb are observed by stopped-flow spectrophotometry, appearing at a rate consistent with the rate, k(obs), of heme-mediated PN decomposition. Freely diffusing NO(2), which is liberated concomitantly from the radical pair (k(e)), preferentially nitrates Tyr103 in horse heart myoglobin. The ratio of the rates of in-cage rebound and cage escape, k(r)/k(e), was found to be approximately 10 by examining the nitration yields of fluorescein, an external NO(2) trap. This rebound/escape model for the metMb/PN interaction is analogous to the behavior of alkyl hyponitrites and the well-studied geminate recombination processes of deoxymyoglobin with O(2), CO, and NO. The scenario is also similar to the stepwise events of substrate hydroxylation by cytochrome P450 and other oxygenases. It is likely, therefore, that the reaction of metMb with ONOO(-) and that of oxyMb with NO proceed through the same [Fe(IV)=O *NO(2)] caged radical intermediate and lead to similar outcomes. The results indicate that while oxyMb may reduce the concentration of intracellular NO, it would not eliminate the formation of NO(2) as a decomposition product of peroxynitrite.
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Affiliation(s)
- Jia Su
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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18
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Repetto EM, Sanchez R, Cipelli J, Astort F, Calejman CM, Piroli GG, Arias P, Cymeryng CB. Dysregulation of corticosterone secretion in streptozotocin-diabetic rats: modulatory role of the adrenocortical nitrergic system. Endocrinology 2010; 151:203-10. [PMID: 19940040 DOI: 10.1210/en.2009-0592] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
An increased activity of the hypothalamo-pituitary-adrenal axis resulting in exaggerated glucocorticoid secretion has been repeatedly described in patients with diabetes mellitus and in animal models of this disease. However, it has been pointed out that experimental diabetes is accompanied by a decreased glucocorticoid response to ACTH stimulation. Because previous studies from our laboratory demonstrate the involvement of nitric oxide (NO) in the modulation of corticosterone production, present investigations were designed to evaluate 1) the impact of streptozotocin (STZ)-induced diabetes on the adrenocortical nitrergic system and 2) the role of NO in the modulation of adrenal steroidogenesis in STZ-diabetic rats. Four weeks after STZ injection, increased activity and expression levels of proteins involved in L-arginine transport and in NO synthesis were detected, and increased levels of thiobarbituric acid reactive species, carbonyl adducts, and nitrotyrosine-modified proteins were measured in the adrenocortical tissue of hyperglycemic rats. An impaired corticosterone response to ACTH was evident both in vivo and in adrenocortical cells isolated from STZ-treated animals. Inhibition of NO synthase activity resulted in higher corticosterone generation in adrenal tissue from STZ-treated rats. Moreover, a stronger inhibition of steroid output from adrenal cells by a NO donor was observed in adrenocortical Y1 cells previously subjected to high glucose (30 mM) treatment. In summary, results presented herein indicate an inhibitory effect of endogenously generated NO on steroid production, probably potentiated by hyperglycemia-induced oxidative stress, in the adrenal cortex of STZ-treated rats.
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Affiliation(s)
- E M Repetto
- Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Centro de Estudios Farmacológicos y Botanicos-Consejo Nacional de Investigaciones Científicas y Técnicas (CEFYBO-CONICET), Buenos Aires, Argentina
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Yuan X, Wang Q, Horner JH, Sheng X, Newcomb M. Kinetics and activation parameters for oxidations of styrene by Compounds I from the cytochrome P450(BM-3) (CYP102A1) heme domain and from CYP119. Biochemistry 2009; 48:9140-6. [PMID: 19708688 DOI: 10.1021/bi901258m] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome P450 (CYP or P450) enzymes are ubiquitous in nature where they catalyze a vast array of oxidation reactions. The active oxidants in P450s have long been assumed to be iron(IV)-oxo porphyrin radical cations termed Compounds I, but P450 Compounds I have proven to be difficult to prepare. The recent development of an entry to these transients by photo-oxidation of the corresponding iron(IV)-oxo neutral porphyrin species (Compounds II) permits spectroscopic and kinetic studies. We report here application of the photo-oxidation method for production of Compound I from the heme domain of CYP102A1 (cytochrome P450(BM-3)), and product and kinetic studies of reactions of styrene with this Compound I transient and also Compound I from CYP119. The studies were performed at low temperatures in 1:1 (v:v) mixtures of glycerol and phosphate buffer. Single-turnover reactions at 0 degrees C gave styrene oxide in good yields. In kinetic studies conducted between -10 and -50 degrees C, both Compounds I displayed saturation kinetics permitting determinations of binding constants and first-order oxidation rate constants. Temperature-dependent functions for the binding constants and rate constants were determined for both Compounds I. In the temperature range studied, the Compound I transient from the CYP102A1 heme domain bound styrene more strongly than Compound I from CYP119, but the rate constants for oxidations of styrene by the latter were somewhat larger than those for the former. The temperature-dependent functions for the first-order oxidation reactions are as follows: log k = 13.2-15.2/2.303RT and log k = 13.3-14.6/2.303RT (kilocalories per mole) for Compounds I from the CYP102A1 heme domain and CYP119, respectively.
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Affiliation(s)
- Xinting Yuan
- Department of Chemistry, University of Illinois, 845 West Taylor Street, Chicago, Illinois 60607, USA
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Sheng X, Horner JH, Newcomb M. Spectra and kinetic studies of the compound I derivative of cytochrome P450 119. J Am Chem Soc 2008; 130:13310-20. [PMID: 18788736 DOI: 10.1021/ja802652b] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Compound I derivative of cytochrome P450 119 (CYP119) was produced by laser flash photolysis of the corresponding Compound II derivative, which was first prepared by reaction of the resting enzyme with peroxynitrite. The UV-vis spectrum of the Compound I species contained an asymmetric Soret band that could be resolved into overlapping transitions centered at approximately 367 and approximately 416 nm and a Q band with lambda(max) approximately 650 nm. Reactions of the Compound I derivative with organic substrates gave epoxidized (alkene oxidation) and hydroxylated (C-H oxidation) products, as demonstrated by product studies and oxygen-18 labeling studies. The kinetics of oxidations by CYP119 Compound I were measured directly; the reactions included hydroxylations of benzyl alcohol, ethylbenzene, Tris buffer, lauric acid, and methyl laurate and epoxidations of styrene and 10-undecenoic acid. Apparent second-order rate constants, equal to the product of the equilibrium binding constant (K(bind)) and the first-order oxidation rate constant (k(ox)), were obtained for all of the substrates. The oxidations of lauric acid and methyl laurate displayed saturation kinetic behavior, which permitted the determination of both K(bind) and k(ox) for these substrates. The unactivated C-H positions of lauric acid reacted with a rate constant of k(ox) = 0.8 s(-1) at room temperature. The CYP119 Compound I derivative is more reactive than model Compound I species [iron(IV)-oxo porphyrin radical cations] and similar in reactivity to the Compound I derivative of the heme-thiolate enzyme chloroperoxidase. Kinetic isotope effects (kH/kD) for oxidations of benzyl alcohol and ethylbenzene were small, reflecting the increased reactivity of the Compound I derivative in comparison to models. Nonetheless, CYP119 Compound I apparently is much less reactive than the oxidizing species formed in the P450 cam reaction cycle. Studies of competition kinetics employing CYP119 activated by hydrogen peroxide indicated that the same oxidizing transient is formed in the photochemical reaction and in the hydrogen peroxide shunt reaction.
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Affiliation(s)
- Xin Sheng
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA
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Replacement of tyrosine residues by phenylalanine in cytochrome P450cam alters the formation of Cpd II-like species in reactions with artificial oxidants. J Biol Inorg Chem 2008; 13:599-611. [DOI: 10.1007/s00775-008-0348-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 01/27/2008] [Indexed: 10/22/2022]
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X-ray absorption spectroscopic characterization of a cytochrome P450 compound II derivative. Proc Natl Acad Sci U S A 2008; 105:8179-84. [PMID: 18174331 DOI: 10.1073/pnas.0708299105] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytochrome P450 enzyme CYP119, its compound II derivative, and its nitrosyl complex were studied by iron K-edge x-ray absorption spectroscopy. The compound II derivative was prepared by reaction of the resting enzyme with peroxynitrite and had a lifetime of approximately 10 s at 23 degrees C. The CYP119 nitrosyl complex was prepared by reaction of the enzyme with nitrogen monoxide gas or with a nitrosyl donor and was stable at 23 degrees C for hours. Samples of CYP119 and its derivatives were studied by x-ray absorption spectroscopy at temperatures below 140 (K) at the Advanced Photon Source of Argonne National Laboratory. The x-ray absorption near-edge structure spectra displayed shifts in edge and pre-edge energies consistent with increasing effective positive charge on iron in the series native CYP119 < CYP119 nitrosyl complex < CYP119 compound II derivative. Extended x-ray absorption fine structure spectra were simulated with good fits for k = 12 A(-1) for native CYP119 and k = 13 A(-1) for both the nitrosyl complex and the compound II derivative. The important structural features for the compound II derivative were an iron-oxygen bond length of 1.82 A and an iron-sulfur bond length of 2.24 A, both of which indicate an iron-oxygen single bond in a ferryl-hydroxide, Fe(IV)OH, moiety.
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