1
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Minerdi D, Sabbatini P. Impact of Cytochrome P450 Enzyme on Fruit Quality. Int J Mol Sci 2024; 25:7181. [PMID: 39000287 PMCID: PMC11241655 DOI: 10.3390/ijms25137181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/20/2024] [Accepted: 06/26/2024] [Indexed: 07/16/2024] Open
Abstract
Cytochrome P450 enzymes are monooxygenases widely diffused in nature ranging from viruses to man. They can catalyze a very wide range of reactions, including the ketonization of C-H bonds, N/O/S-dealkylation, C-C bond cleavage, N/S-oxidation, hydroxylation, and the epoxidation of C=C bonds. Their versatility makes them valuable across various fields such as medicine, chemistry, and food processing. In this review, we aim to highlight the significant contribution of P450 enzymes to fruit quality, with a specific focus on the ripening process, particularly in grapevines. Grapevines are of particular interest due to their economic importance in the fruit industry and their significance in winemaking. Understanding the role of P450 enzymes in grapevine fruit ripening can provide insights into enhancing grape quality, flavor, and aroma, which are critical factors in determining the market value of grapes and derived products like wine. Moreover, the potential of P450 enzymes extends beyond fruit ripening. They represent promising candidates for engineering crop species that are resilient to both biotic and abiotic stresses. Their involvement in metabolic engineering offers opportunities for enhancing fruit quality attributes, such as taste, nutritional content, and shelf life. Harnessing the capabilities of P450 enzymes in crop improvement holds immense promise for sustainable agriculture and food security.
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Affiliation(s)
- Daniela Minerdi
- Department of Agricultural, Forestry and Food Sciences, University of Turin, Largo Paolo Braccini 2, 10095 Grugliasco, TO, Italy;
| | - Paolo Sabbatini
- Department of Agricultural, Forestry and Food Sciences, University of Turin, Largo Paolo Braccini 2, 10095 Grugliasco, TO, Italy;
- Department of Horticulture, Michigan State University, East Lansing, MI 48824, USA
- Interdepartmental Centre for Grapevines and Wine Sciences, University of Turin, Corso Enotria 2/C, 12051 Alba, CN, Italy
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2
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Kanematsu Y, Kondo HX, Takano Y. Computational Exploration of Minimum Energy Reaction Pathway of N 2O Formation from Intermediate I of P450nor Using an Active Center Model. Int J Mol Sci 2023; 24:17172. [PMID: 38139001 PMCID: PMC10743073 DOI: 10.3390/ijms242417172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 11/30/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
P450nor is a heme-containing enzyme that catalyzes the conversion of nitric oxide (NO) to nitrous oxide (N2O). Its catalytic mechanism has attracted attention in chemistry, biology, and environmental engineering. The catalytic cycle of P450nor is proposed to consist of three major steps. The reaction mechanism for the last step, N2O generation, remains unknown. In this study, the reaction pathway of the N2O generation from the intermediate I was explored with the B3LYP calculations using an active center model after the examination of the validity of the model. In the validation, we compared the heme distortions between P450nor and other oxidoreductases, suggesting a small effect of protein environment on the N2O generation reaction in P450nor. We then evaluated the electrostatic environment effect of P450nor on the hydride affinity to the active site with quantum mechanics/molecular mechanics (QM/MM) calculations, confirming that the affinity was unchanged with or without the protein environment. The active center model for P450nor showed that the N2O generation process in the enzymatic reaction undergoes a reasonable barrier height without protein environment. Consequently, our findings strongly suggest that the N2O generation reaction from the intermediate I depends sorely on the intrinsic reactivity of the heme cofactor bound on cysteine residue.
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Affiliation(s)
- Yusuke Kanematsu
- Graduate School of Advanced Science and Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan
- Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozukahigashi Asaminamiku, Hiroshima 731-3194, Japan;
| | - Hiroko X. Kondo
- Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozukahigashi Asaminamiku, Hiroshima 731-3194, Japan;
- Faculty of Engineering, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507, Japan
| | - Yu Takano
- Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozukahigashi Asaminamiku, Hiroshima 731-3194, Japan;
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3
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Park J, Kim J, Jeong GY, Kim Y, Lee E. Uncovering Nitrosyl Reactivity at N-Heterocyclic Carbene Center. Angew Chem Int Ed Engl 2023:e202314978. [PMID: 37917039 DOI: 10.1002/anie.202314978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 10/31/2023] [Accepted: 11/02/2023] [Indexed: 11/03/2023]
Abstract
N-heterocyclic carbenes (NHCs) have garnered much attention due to their unique properties, such as strong σ-donating and π-accepting abilities, as well as their transition-metal-like reactivity toward small molecules. In 2015, we discovered that NHCs can react with nitric oxide (NO) gas to form radical adducts that resemble transition metal nitrosyl complexes. To elucidate the analogy between NHC and transition metal NO adducts, here we have undertaken a systematic investigation of the electron- and proton-transfer chemistry of [NHC-NO]⋅ (N-heterocyclic carbene nitric oxide radical) compounds. We have accessed a suite of compounds, comprised of [NHC-NO]+ , [NHC-NO]- , [NHC-NOH]0 , and [NHC-NHOH]+ species. In particular, [NHC-NO]- was isolated as potassium and lithium ion adducts. Most interestingly, a monomeric potassium [NHC-NO]- compound was isolated with the assistance of 18-crown-6, which is the first instance of a monomeric alkali N-oxyl compound to the best of our knowledge. Our results demonstrate that [NHC-NO]⋅ exhibits redox behavior broadly similar to metal nitrosyl complexes, which opens up more possibilities for utilizing NHCs to build on the known reactivity of metal complexes.
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Affiliation(s)
- Junbeom Park
- Department of Chemistry, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Jaelim Kim
- Department of Chemistry, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Gu Yoon Jeong
- Department of Chemistry, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Youngsuk Kim
- Department of Chemistry, Pusan National University, Busan, 46241, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
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4
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Manickas EC, LaLonde AB, Hu MY, Alp EE, Lehnert N. Stabilization of a Heme-HNO Model Complex Using a Bulky Bis-Picket Fence Porphyrin and Reactivity Studies with NO. J Am Chem Soc 2023; 145:23014-23026. [PMID: 37824502 DOI: 10.1021/jacs.3c05333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Nitroxyl, HNO/NO-, the one-electron reduced form of NO, is suggested to take part in distinct signaling pathways in mammals and is also a key intermediate in various heme-catalyzed NOx interconversions in the nitrogen cycle. Cytochrome P450nor (Cyt P450nor) is a heme-containing enzyme that performs NO reduction to N2O in fungal denitrification. The reactive intermediate in this enzyme, termed "Intermediate I", is proposed to be an Fe-NHO/Fe-NHOH type species, but it is difficult to study its electronic structure and exact protonation state due to its instability. Here, we utilize a bulky bis-picket fence porphyrin to obtain the first stable heme-HNO model complex, [Fe(3,5-Me-BAFP)(MI)(NHO)], as a model for Intermediate I, and more generally HNO adducts of heme proteins. Due to the steric hindrance of the bis-picket fence porphyrin, [Fe(3,5-Me-BAFP)(MI)(NHO)] is stable (τ1/2 = 56 min at -30 °C), can be isolated as a solid, and is available for thorough spectroscopic characterization. In particular, we were able to solve a conundrum in the literature and provide the first full vibrational characterization of a heme-HNO complex using IR and nuclear resonance vibrational spectroscopy (NRVS). Reactivity studies of [Fe(3,5-Me-BAFP)(MI)(NHO)] with NO gas show a 91 ± 10% yield for N2O formation, demonstrating that heme-HNO complexes are catalytically competent intermediates for NO reduction to N2O in Cyt P450nor. The implications of these results for the mechanism of Cyt P450nor are further discussed.
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Affiliation(s)
- Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Ashley B LaLonde
- Department of Chemistry and Department of Biophysics, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Michael Y Hu
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, Illinois 60439, United States
| | - E Ercan Alp
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, Illinois 60439, United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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5
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Rajakumara E, Saniya D, Bajaj P, Rajeshwari R, Giri J, Davari MD. Hijacking Chemical Reactions of P450 Enzymes for Altered Chemical Reactions and Asymmetric Synthesis. Int J Mol Sci 2022; 24:ijms24010214. [PMID: 36613657 PMCID: PMC9820634 DOI: 10.3390/ijms24010214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 12/09/2022] [Accepted: 12/12/2022] [Indexed: 12/25/2022] Open
Abstract
Cytochrome P450s are heme-containing enzymes capable of the oxidative transformation of a wide range of organic substrates. A protein scaffold that coordinates the heme iron, and the catalytic pocket residues, together, determine the reaction selectivity and regio- and stereo-selectivity of the P450 enzymes. Different substrates also affect the properties of P450s by binding to its catalytic pocket. Modulating the redox potential of the heme by substituting iron-coordinating residues changes the chemical reaction, the type of cofactor requirement, and the stereoselectivity of P450s. Around hundreds of P450s are experimentally characterized, therefore, a mechanistic understanding of the factors affecting their catalysis is increasingly vital in the age of synthetic biology and biotechnology. Engineering P450s can enable them to catalyze a variety of chemical reactions viz. oxygenation, peroxygenation, cyclopropanation, epoxidation, nitration, etc., to synthesize high-value chiral organic molecules with exceptionally high stereo- and regioselectivity and catalytic efficiency. This review will focus on recent studies of the mechanistic understandings of the modulation of heme redox potential in the engineered P450 variants, and the effect of small decoy molecules, dual function small molecules, and substrate mimetics on the type of chemical reaction and the catalytic cycle of the P450 enzymes.
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Affiliation(s)
- Eerappa Rajakumara
- Macromolecular Structural Biology Lab, Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, India
- Correspondence: (E.R.); (M.D.D.)
| | - Dubey Saniya
- Macromolecular Structural Biology Lab, Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, India
| | - Priyanka Bajaj
- Department of Chemical Sciences, National Institute of Pharmaceutical Education and Research (NIPER), NH-44, Balanagar, Hyderabad 500037, India
| | - Rajanna Rajeshwari
- Department of Plant Pathology, College of Horticulture, University of Horticultural Sciences, Bagalkot Campus, GKVK, Bengaluru 560064, India
| | - Jyotsnendu Giri
- Department of Biomedical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, India
| | - Mehdi D. Davari
- Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle, Germany
- Correspondence: (E.R.); (M.D.D.)
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6
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Lehnert N, Kim E, Dong HT, Harland JB, Hunt AP, Manickas EC, Oakley KM, Pham J, Reed GC, Alfaro VS. The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity. Chem Rev 2021; 121:14682-14905. [PMID: 34902255 DOI: 10.1021/acs.chemrev.1c00253] [Citation(s) in RCA: 96] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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7
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Short-lived intermediate in N 2O generation by P450 NO reductase captured by time-resolved IR spectroscopy and XFEL crystallography. Proc Natl Acad Sci U S A 2021; 118:2101481118. [PMID: 34001620 DOI: 10.1073/pnas.2101481118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nitric oxide (NO) reductase from the fungus Fusarium oxysporum is a P450-type enzyme (P450nor) that catalyzes the reduction of NO to nitrous oxide (N2O) in the global nitrogen cycle. In this enzymatic reaction, the heme-bound NO is activated by the direct hydride transfer from NADH to generate a short-lived intermediate ( I ), a key state to promote N-N bond formation and N-O bond cleavage. This study applied time-resolved (TR) techniques in conjunction with photolabile-caged NO to gain direct experimental results for the characterization of the coordination and electronic structures of I TR freeze-trap crystallography using an X-ray free electron laser (XFEL) reveals highly bent Fe-NO coordination in I , with an elongated Fe-NO bond length (Fe-NO = 1.91 Å, Fe-N-O = 138°) in the absence of NAD+ TR-infrared (IR) spectroscopy detects the formation of I with an N-O stretching frequency of 1,290 cm-1 upon hydride transfer from NADH to the Fe3+-NO enzyme via the dissociation of NAD+ from a transient state, with an N-O stretching of 1,330 cm-1 and a lifetime of ca. 16 ms. Quantum mechanics/molecular mechanics calculations, based on these crystallographic and IR spectroscopic results, demonstrate that the electronic structure of I is characterized by a singly protonated Fe3+-NHO•- radical. The current findings provide conclusive evidence for the N2O generation mechanism via a radical-radical coupling of the heme nitroxyl complex with the second NO molecule.
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8
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Kim DH, Ringe S, Kim H, Kim S, Kim B, Bae G, Oh HS, Jaouen F, Kim W, Kim H, Choi CH. Selective electrochemical reduction of nitric oxide to hydroxylamine by atomically dispersed iron catalyst. Nat Commun 2021; 12:1856. [PMID: 33767159 PMCID: PMC7994811 DOI: 10.1038/s41467-021-22147-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 02/19/2021] [Indexed: 12/03/2022] Open
Abstract
Electrocatalytic conversion of nitrogen oxides to value-added chemicals is a promising strategy for mitigating the human-caused unbalance of the global nitrogen-cycle, but controlling product selectivity remains a great challenge. Here we show iron-nitrogen-doped carbon as an efficient and durable electrocatalyst for selective nitric oxide reduction into hydroxylamine. Using in operando spectroscopic techniques, the catalytic site is identified as isolated ferrous moieties, at which the rate for hydroxylamine production increases in a super-Nernstian way upon pH decrease. Computational multiscale modelling attributes the origin of unconventional pH dependence to the redox active (non-innocent) property of NO. This makes the rate-limiting NO adsorbate state more sensitive to surface charge which varies with the pH-dependent overpotential. Guided by these fundamental insights, we achieve a Faradaic efficiency of 71% and an unprecedented production rate of 215 μmol cm-2 h-1 at a short-circuit mode in a flow-type fuel cell without significant catalytic deactivation over 50 h operation.
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Affiliation(s)
- Dong Hyun Kim
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Stefan Ringe
- Department of Energy Science and Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu, Republic of Korea
| | - Haesol Kim
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Sejun Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Bupmo Kim
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Geunsu Bae
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Hyung-Suk Oh
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea
| | - Frédéric Jaouen
- ICGM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Wooyul Kim
- Department of Chemical and Biological Engineering, Sookmyung Women's University, Seoul, Republic of Korea.
| | - Hyungjun Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.
| | - Chang Hyuck Choi
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
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9
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Abstract
Ammonia-oxidizing bacteria (AOB) convert ammonia (NH3) to nitrite (NO2-) as their primary metabolism and thus provide a blueprint for the use of NH3 as a chemical fuel. The first energy-producing step involves the homotrimeric enzyme hydroxylamine oxidoreductase (HAO), which was originally reported to oxidize hydroxylamine (NH2OH) to NO2-. HAO uses the heme P460 cofactor as the site of catalysis. This heme is supported by seven other c hemes in each monomer that mediate electron transfer. Heme P460 cofactors are c-heme-based cofactors that have atypical protein cross-links between the peptide backbone and the porphyrin macrocycle. This cofactor has been observed in both the HAO and cytochrome (cyt) P460 protein families. However, there are differences; specifically, HAO uses a single tyrosine residue to form two covalent attachments to the macrocycle whereas cyt P460 uses a lysine residue to form one. In Nitrosomonas europaea, which expresses both HAO and cyt P460, these enzymes achieve the oxidation of NH2OH and were both originally reported to produce NO2-. Each can inspire means to effect controlled release of chemical energy.Spectroscopically studying the P460 cofactors of HAO is complicated by the 21 non-P460 heme cofactors, which obscure the active site. However, monoheme cyt P460 is more approachable biochemically and spectroscopically. Thus, we have used cyt P460 to study biological NH2OH oxidation. Under aerobic conditions substoichiometric production of NO2- was observed along with production of nitrous oxide (N2O). Under anaerobic conditions, however, N2O was the exclusive product of NH2OH oxidation. We have advanced our understanding of the mechanism of this enzyme and have showed that a key intermediate is a ferric nitrosyl that can dissociate the bound nitric oxide (NO) molecule and react with O2, thus producing NO2- abiotically. Because N2O was the true product of one P460 cofactor-containing enzyme, this prompted us to reinvestigate whether NO2- is enzymatically generated from HAO catalysis. Like cyt P460, we showed that HAO does not produce NO2- enzymatically, but unlike cyt P460, its final product is NO, establishing it as an intermediate of nitrification. More broadly, NO can be recognized as a molecule common to the primary metabolisms of all organisms involved in nitrogen "defixation".Delving deeper into cyt P460 yielded insights broadly applicable to controlled biochemical redox processes. Studies of an inactive cyt P460 from Nitrosomonas sp. AL212 showed that this enzyme was unable to oxidize NH2OH because it lacked a glutamate residue in its secondary coordination sphere that was present in the active N. europaea cyt P460 variant. Restoring the Glu residue imbued activity, revealing that a second-sphere base is Nature's key to controlled oxidation of NH2OH. A key lesson of bioinorganic chemistry is reinforced: the polypeptide matrix is an essential part of dictating function. Our work also exposed some key functional contributions of noncanonical heme-protein cross-links. The heme-Lys cross-link of cyt P460 enforces the relative position of the cofactor and second-sphere residues. Moreover, the cross-link prevents the dissociation of the axial histidine residue, which stops catalysis, emphasizing the importance of this unique post-translational modification.
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Affiliation(s)
- Rachael E. Coleman
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Kyle M. Lancaster
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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10
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Ferousi C, Majer SH, DiMucci IM, Lancaster KM. Biological and Bioinspired Inorganic N-N Bond-Forming Reactions. Chem Rev 2020; 120:5252-5307. [PMID: 32108471 PMCID: PMC7339862 DOI: 10.1021/acs.chemrev.9b00629] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The metallobiochemistry underlying the formation of the inorganic N-N-bond-containing molecules nitrous oxide (N2O), dinitrogen (N2), and hydrazine (N2H4) is essential to the lifestyles of diverse organisms. Similar reactions hold promise as means to use N-based fuels as alternative carbon-free energy sources. This review discusses research efforts to understand the mechanisms underlying biological N-N bond formation in primary metabolism and how the associated reactions are tied to energy transduction and organismal survival. These efforts comprise studies of both natural and engineered metalloenzymes as well as synthetic model complexes.
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Affiliation(s)
- Christina Ferousi
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Sean H Majer
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Ida M DiMucci
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
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11
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Smith MA, Majer SH, Vilbert AC, Lancaster KM. Controlling a burn: outer-sphere gating of hydroxylamine oxidation by a distal base in cytochrome P460. Chem Sci 2019; 10:3756-3764. [PMID: 31015919 PMCID: PMC6457333 DOI: 10.1039/c9sc00195f] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 02/14/2019] [Indexed: 01/19/2023] Open
Abstract
One amino acid makes the difference between a metalloenzyme and a metalloprotein in two otherwise effectively identical cytochrome P460s.
Ammonia oxidizing bacteria (AOB) use the cytotoxic, energetic molecule hydroxylamine (NH2OH) as a source of reducing equivalents for cellular respiration. Despite disproportionation or violent decomposition being typical outcomes of reactions of NH2OH with iron, AOB and anammox heme P460 proteins including cytochrome (cyt) P460 and hydroxylamine oxidoreductase (HAO) effect controlled, stepwise oxidation of NH2OH to nitric oxide (NO). Curiously, a recently characterized cyt P460 variant from the AOB Nitrosomonas sp. AL212 is able to form all intermediates of cyt P460 catalysis, but is nevertheless incompetent for NH2OH oxidation. We now show via site-directed mutagenesis, activity assays, spectroscopy, and structural biology that this lack of activity is attributable to the absence of a critical basic glutamate residue in the distal pocket above the heme P460 cofactor. This substitution is the only distinguishing characteristic of a protein that is otherwise effectively structurally and spectroscopically identical to an active variant. This highlights and reinforces a fundamental principal of metalloenzymology: metallocofactor inner-sphere geometric and electronic structures are in many cases insufficient for imbuing reactivity; a precisely defined outer coordination sphere contributed by the polypeptide matrix can be the key differentiator between a metalloenzyme and an unreactive metalloprotein.
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Affiliation(s)
- Meghan A Smith
- Department of Chemistry and Chemical Biology , Baker Laboratory , Cornell University , Ithaca , NY 14853 , USA .
| | - Sean H Majer
- Department of Chemistry and Chemical Biology , Baker Laboratory , Cornell University , Ithaca , NY 14853 , USA .
| | - Avery C Vilbert
- Department of Chemistry and Chemical Biology , Baker Laboratory , Cornell University , Ithaca , NY 14853 , USA .
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology , Baker Laboratory , Cornell University , Ithaca , NY 14853 , USA .
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12
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McQuarters AB, Blaesi EJ, Kampf JW, Alp EE, Zhao J, Hu M, Krebs C, Lehnert N. Synthetic Model Complex of the Key Intermediate in Cytochrome P450 Nitric Oxide Reductase. Inorg Chem 2019; 58:1398-1413. [PMID: 30623648 DOI: 10.1021/acs.inorgchem.8b02947] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fungal denitrification plays a crucial role in the nitrogen cycle and contributes to the total N2O emission from agricultural soils. Here, cytochrome P450 NO reductase (P450nor) reduces two NO to N2O using a single heme site. Despite much research, the exact nature of the critical "Intermediate I" responsible for the key N-N coupling step in P450nor is unknown. This species likely corresponds to a Fe-NHOH-type intermediate with an unknown electronic structure. Here we report a new strategy to generate a model system for this intermediate, starting from the iron(III) methylhydroxylamide complex [Fe(3,5-Me-BAFP)(NHOMe)] (1), which was fully characterized by 1H NMR, UV-vis, electron paramagnetic resonance, and vibrational spectroscopy (rRaman and NRVS). Our data show that 1 is a high-spin ferric complex with an N-bound hydroxylamide ligand that is strongly coordinated (Fe-N distance, 1.918 Å; Fe-NHOMe stretch, 558 cm-1). Simple one-electron oxidation of 1 at -80 °C then cleanly generates the first model system for Intermediate I, [Fe(3,5-Me-BAFP)(NHOMe)]+ (1+). UV-vis, resonance Raman, and Mössbauer spectroscopies, in comparison to the chloro analogue [Fe(3,5-Me-BAFP)(Cl)]+, demonstrate that 1+ is best described as an FeIII-(NHOMe)• complex with a bound NHOMe radical. Further reactivity studies show that 1+ is highly reactive toward NO, a reaction that likely proceeds via N-N bond formation, following a radical-radical-type coupling mechanism. Our results therefore provide experimental evidence, for the first time, that an FeIII-(NHOMe)• electronic structure is indeed a reasonable electronic description for Intermediate I and that this electronic structure is advantageous for P450nor catalysis because it can greatly facilitate N-N bond formation and, ultimately, N2O generation.
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Affiliation(s)
- Ashley B McQuarters
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Elizabeth J Blaesi
- Department of Chemistry and Department of Biochemistry and Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Jeff W Kampf
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - E Ercan Alp
- Advanced Photon Source (APS) , Argonne National Laboratory (ANL) , Argonne , Illinois 60439 , United States
| | - Jiyong Zhao
- Advanced Photon Source (APS) , Argonne National Laboratory (ANL) , Argonne , Illinois 60439 , United States
| | - Michael Hu
- Advanced Photon Source (APS) , Argonne National Laboratory (ANL) , Argonne , Illinois 60439 , United States
| | - Carsten Krebs
- Department of Chemistry and Department of Biochemistry and Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109 , United States
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13
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Preimesberger MR, Johnson EA, Nye DB, Lecomte JTJ. Covalent attachment of the heme to Synechococcus hemoglobin alters its reactivity toward nitric oxide. J Inorg Biochem 2017; 177:171-182. [PMID: 28968520 DOI: 10.1016/j.jinorgbio.2017.09.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 09/18/2017] [Accepted: 09/19/2017] [Indexed: 01/19/2023]
Abstract
The cyanobacterium Synechococcus sp. PCC 7002 produces a monomeric hemoglobin (GlbN) implicated in the detoxification of reactive nitrogen and oxygen species. GlbN contains a b heme, which can be modified under certain reducing conditions. The modified protein (GlbN-A) has one heme-histidine C-N linkage similar to the C-S linkage of cytochrome c. No clear functional role has been assigned to this modification. Here, optical absorbance and NMR spectroscopies were used to compare the reactivity of GlbN and GlbN-A toward nitric oxide (NO). Both forms of the protein are capable of NO dioxygenase activity and both undergo heme bleaching after multiple NO challenges. GlbN and GlbN-A bind NO in the ferric state and form diamagnetic complexes (FeIII-NO) that resist reductive nitrosylation to the paramagnetic FeII-NO forms. Dithionite reduction of FeIII-NO GlbN and GlbN-A, however, resulted in distinct outcomes. Whereas GlbN-A rapidly formed the expected FeII-NO complex, NO binding to FeII GlbN caused immediate heme loss and, remarkably, was followed by slow heme rebinding and HNO (nitrosyl hydride) production. Additionally, combining FeIII GlbN, 15N-labeled nitrite, and excess dithionite resulted in the formation of FeII-H15NO GlbN. Dithionite-mediated HNO production was also observed for the related GlbN from Synechocystis sp. PCC 6803. Although ferrous GlbN-A appeared capable of trapping preformed HNO, the histidine-heme post-translational modification extinguished the NO reduction chemistry associated with GlbN. Overall, the results suggest a role for the covalent modification in FeII GlbNs: protection from NO-mediated heme loss and prevention of HNO formation.
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Affiliation(s)
| | - Eric A Johnson
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Dillon B Nye
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Juliette T J Lecomte
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.
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14
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Ciaramella A, Minerdi D, Gilardi G. Catalytically self-sufficient cytochromes P450 for green production of fine chemicals. RENDICONTI LINCEI-SCIENZE FISICHE E NATURALI 2016. [DOI: 10.1007/s12210-016-0581-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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15
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Nitrosomonas europaea cytochrome P460 is a direct link between nitrification and nitrous oxide emission. Proc Natl Acad Sci U S A 2016; 113:14704-14709. [PMID: 27856762 DOI: 10.1073/pnas.1611051113] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ammonia oxidizing bacteria (AOB) are major contributors to the emission of nitrous oxide (N2O). It has been proposed that N2O is produced by reduction of NO. Here, we report that the enzyme cytochrome (cyt) P460 from the AOB Nitrosomonas europaea converts hydroxylamine (NH2OH) quantitatively to N2O under anaerobic conditions. Previous literature reported that this enzyme oxidizes NH2OH to nitrite ([Formula: see text]) under aerobic conditions. Although we observe [Formula: see text] formation under aerobic conditions, its concentration is not stoichiometric with the NH2OH concentration. By contrast, under anaerobic conditions, the enzyme uses 4 oxidizing equivalents (eq) to convert 2 eq of NH2OH to N2O. Enzyme kinetics coupled to UV/visible absorption and electron paramagnetic resonance (EPR) spectroscopies support a mechanism in which an FeIII-NH2OH adduct of cyt P460 is oxidized to an {FeNO}6 unit. This species subsequently undergoes nucleophilic attack by a second equivalent of NH2OH, forming the N-N bond of N2O during a bimolecular, rate-determining step. We propose that [Formula: see text] results when nitric oxide (NO) dissociates from the {FeNO}6 intermediate and reacts with dioxygen. Thus, [Formula: see text] is not a direct product of cyt P460 activity. We hypothesize that the cyt P460 oxidation of NH2OH contributes to NO and N2O emissions from nitrifying microorganisms.
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16
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Ortmayer M, Lafite P, Menon BRK, Tralau T, Fisher K, Denkhaus L, Scrutton NS, Rigby SEJ, Munro AW, Hay S, Leys D. An oxidative N-demethylase reveals PAS transition from ubiquitous sensor to enzyme. Nature 2016; 539:593-597. [PMID: 27851736 DOI: 10.1038/nature20159] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 10/15/2016] [Indexed: 12/14/2022]
Abstract
The universal Per-ARNT-Sim (PAS) domain functions as a signal transduction module involved in sensing diverse stimuli such as small molecules, light, redox state and gases. The highly evolvable PAS scaffold can bind a broad range of ligands, including haem, flavins and metal ions. However, although these ligands can support catalytic activity, to our knowledge no enzymatic PAS domain has been found. Here we report characterization of the first PAS enzyme: a haem-dependent oxidative N-demethylase. Unrelated to other amine oxidases, this enzyme contains haem, flavin mononucleotide, 2Fe-2S and tetrahydrofolic acid cofactors, and specifically catalyses the NADPH-dependent oxidation of dimethylamine. The structure of the α subunit reveals that it is a haem-binding PAS domain, similar in structure to PAS gas sensors. The dimethylamine substrate forms part of a highly polarized oxygen-binding site, and directly assists oxygen activation by acting as both an electron and proton donor. Our data reveal that the ubiquitous PAS domain can make the transition from sensor to enzyme, suggesting that the PAS scaffold can support the development of artificial enzymes.
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Affiliation(s)
- Mary Ortmayer
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Pierre Lafite
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Binuraj R K Menon
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Tewes Tralau
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Karl Fisher
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Lukas Denkhaus
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Andrew W Munro
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - Sam Hay
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
| | - David Leys
- Manchester Institute of Biotechnology, School of Chemistry, 131 Princess Street, University of Manchester, Manchester M1 7DN, UK
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Walter MR, Dzul SP, Rodrigues AV, Stemmler TL, Telser J, Conradie J, Ghosh A, Harrop TC. Synthesis of CoII–NO– Complexes and Their Reactivity as a Source of Nitroxyl. J Am Chem Soc 2016; 138:12459-71. [DOI: 10.1021/jacs.6b05896] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Melody R. Walter
- Department
of Chemistry and Center for Metalloenzyme Studies, The University of Georgia, 140 Cedar Street, Athens, Georgia 30602, United States
| | - Stephen P. Dzul
- Departments
of Pharmaceutical Sciences, Biochemistry, and Molecular Biology, Wayne State University, Detroit, Michigan 48201, United States
| | - Andria V. Rodrigues
- Departments
of Pharmaceutical Sciences, Biochemistry, and Molecular Biology, Wayne State University, Detroit, Michigan 48201, United States
| | - Timothy L. Stemmler
- Departments
of Pharmaceutical Sciences, Biochemistry, and Molecular Biology, Wayne State University, Detroit, Michigan 48201, United States
| | - Joshua Telser
- Department
of Biological, Chemical, and Physical Sciences, Roosevelt University, 430 South Michigan Avenue, Chicago, Illinois 60605, United States
| | - Jeanet Conradie
- Department
of Chemistry, University of the Free State, 9300 Bloemfontein, Republic of South Africa
| | - Abhik Ghosh
- Department
of Chemistry and Center for Theoretical and
Computational Chemistry, University of Tromsø, N-9037 Tromsø, Norway
| | - Todd C. Harrop
- Department
of Chemistry and Center for Metalloenzyme Studies, The University of Georgia, 140 Cedar Street, Athens, Georgia 30602, United States
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18
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Pardillo AD, Morozov AN, Chatfield DC. Proximal Pocket Hydrogen Bonds Significantly Influence the Mechanism of Chloroperoxidase Compound I Formation. J Phys Chem B 2015; 119:12590-602. [DOI: 10.1021/acs.jpcb.5b06324] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Armando D. Pardillo
- Department of Chemistry and
Biochemistry, Florida International University, 11200 SW 8th Street, Miami, Florida 33199, United States
| | - Alexander N. Morozov
- Department of Chemistry and
Biochemistry, Florida International University, 11200 SW 8th Street, Miami, Florida 33199, United States
| | - David C. Chatfield
- Department of Chemistry and
Biochemistry, Florida International University, 11200 SW 8th Street, Miami, Florida 33199, United States
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19
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Lee T, Hwang S, Lim M. Picosecond Dynamics of Photoexcited DNO-Bound Myoglobin Probed by Femtosecond Vibrational Spectroscopy. J Phys Chem B 2015; 119:1814-22. [DOI: 10.1021/jp509644m] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Taegon Lee
- Department
of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea
| | - Sungu Hwang
- Department
of Applied Nanoscience, Pusan National University, Miryang 627-706, Korea
| | - Manho Lim
- Department
of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea
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20
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Das AB, Nauser T, Koppenol WH, Kettle AJ, Winterbourn CC, Nagy P. Rapid reaction of superoxide with insulin-tyrosyl radicals to generate a hydroperoxide with subsequent glutathione addition. Free Radic Biol Med 2014; 70:86-95. [PMID: 24561577 DOI: 10.1016/j.freeradbiomed.2014.02.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 01/28/2014] [Accepted: 02/05/2014] [Indexed: 10/25/2022]
Abstract
Tyrosine (Tyr) residues are major sites of radical generation during protein oxidation. We used insulin as a model to study the kinetics, mechanisms, and products of the reactions of radiation-induced or enzyme-generated protein-tyrosyl radicals with superoxide to demonstrate the feasibility of these reactions under oxidative stress conditions. We found that insulin-tyrosyl radicals combined to form dimers, mostly via the tyrosine at position 14 on the α chain (Tyr14). However, in the presence of superoxide, dimerization was largely outcompeted by the reaction of superoxide with insulin-tyrosyl radicals. Using pulse radiolysis, we measured a second-order rate constant for the latter reaction of (6±1) × 10(8) M(-1) s(-1) at pH 7.3, representing the first measured rate constant for a protein-tyrosyl radical with superoxide. Mass-spectrometry-based product analyses revealed the addition of superoxide to the insulin-Tyr14 radical to form the hydroperoxide. Glutathione efficiently reduced the hydroperoxide to the corresponding monoxide and also subsequently underwent Michael addition to the monoxide to give a diglutathionylated protein adduct. Although much slower, conjugation of the backbone amide group can form a bicyclic Tyr-monoxide derivative, allowing the addition of only one glutathione molecule. These findings suggest that Tyr-hydroperoxides should readily form on proteins under oxidative stress conditions where protein radicals and superoxide are both generated and that these should form addition products with thiol compounds such as glutathione.
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Affiliation(s)
- Andrew B Das
- Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch, Christchurch 8140, New Zealand
| | - Thomas Nauser
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8092 Zurich, Switzerland
| | - Willem H Koppenol
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8092 Zurich, Switzerland
| | - Anthony J Kettle
- Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch, Christchurch 8140, New Zealand
| | - Christine C Winterbourn
- Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch, Christchurch 8140, New Zealand
| | - Péter Nagy
- Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch, Christchurch 8140, New Zealand.
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21
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Speelman AL, Lehnert N. Heme versus non-heme iron-nitroxyl {FeN(H)O}⁸ complexes: electronic structure and biologically relevant reactivity. Acc Chem Res 2014; 47:1106-16. [PMID: 24555413 DOI: 10.1021/ar400256u] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Researchers have completed extensive studies on heme and non-heme iron-nitrosyl complexes, which are labeled {FeNO}(7) in the Enemark-Feltham notation, but they have had very limited success in producing corresponding, one-electron reduced, {FeNO}(8) complexes where a nitroxyl anion (NO(-)) is formally bound to an iron(II) center. These complexes, and their protonated iron(II)-NHO analogues, are proposed key intermediates in nitrite (NO2(-)) and nitric oxide (NO) reducing enzymes in bacteria and fungi. In addition, HNO is known to have a variety of physiological effects, most notably in the cardiovascular system. HNO may also serve as a signaling molecule in mammals. For these functions, iron-containing proteins may mediate the production of HNO and serve as receptors for HNO in vivo. In this Account, we highlight recent key advances in the preparation, spectroscopic characterization, and reactivity of ferrous heme and non-heme nitroxyl (NO(-)/HNO) complexes that have greatly enhanced our understanding of the potential biological roles of these species. Low-spin (ls) heme {FeNO}(7) complexes (S = 1/2) can be reversibly reduced to the corresponding {FeNO}(8) species, which are stable, diamagnetic compounds. Because the reduction is ligand (NO) centered in these cases, it occurs at extremely negative redox potentials that are at the edge of the biologically feasible range. Interestingly, the electronic structures of ls-{FeNO}(7) and ls-{FeNO}(8) species are strongly correlated with very similar frontier molecular orbitals (FMOs) and thermodynamically strong Fe-NO bonds. In contrast, high-spin (hs) non-heme {FeNO}(7) complexes (S = 3/2) can be reduced at relatively mild redox potentials. Here, the reduction is metal-centered and leads to a paramagnetic (S = 1) {FeNO}(8) complex. The increased electron density at the iron center in these species significantly decreases the covalency of the Fe-NO bond, making the reduced complexes highly reactive. In the absence of steric bulk, monomeric high-spin {FeNO}(8) complexes decompose rapidly. Notably, in a recently prepared, dimeric [{FeNO}(7)]2 species, we observed that reduction leads to rapid N-N bond formation and N2O generation, which directly models the reactivity of flavodiiron NO reductases (FNORs). We have also made key progress in the preparation and stabilization of corresponding HNO complexes, {FeNHO}(8), using both heme and non-heme ligand sets. In both cases, we have taken advantage of sterically bulky coligands to stabilize these species. ls-{FeNO}(8) complexes are basic and easily form corresponding ls-{FeNHO}(8) species, which, however, decompose rapidly via disproportionation and H2 release. Importantly, we recently showed that we can suppress this reaction via steric protection of the bound HNO ligand. As a result, we have demonstrated that ls-{FeNHO}(8) model complexes are stable and amenable to spectroscopic characterization. Neither ls-{FeNO}(8) nor ls-{FeNHO}(8) model complexes are active for N-N coupling, and hence, seem unsuitable as reactive intermediates in nitric oxide reductases (NORs). Hs-{FeNO}(8) complexes are more basic than their hs-{FeNO}(7) precursors, but their electronic structure and reactivity is not as well characterized.
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Affiliation(s)
- Amy L. Speelman
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nicolai Lehnert
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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22
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Model complexes of key intermediates in fungal cytochrome P450 nitric oxide reductase (P450nor). Curr Opin Chem Biol 2014; 19:82-9. [DOI: 10.1016/j.cbpa.2014.01.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Revised: 01/18/2014] [Accepted: 01/20/2014] [Indexed: 11/19/2022]
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23
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Riplinger C, Bill E, Daiber A, Ullrich V, Shoun H, Neese F. New Insights into the Nature of Observable Reaction Intermediates in Cytochrome P450 NO Reductase by Using a Combination of Spectroscopy and Quantum Mechanics/Molecular Mechanics Calculations. Chemistry 2014; 20:1602-14. [DOI: 10.1002/chem.201302443] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 11/04/2013] [Indexed: 11/08/2022]
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24
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Quantum mechanical modeling: a tool for the understanding of enzyme reactions. Biomolecules 2013; 3:662-702. [PMID: 24970187 PMCID: PMC4030948 DOI: 10.3390/biom3030662] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 09/17/2013] [Accepted: 09/19/2013] [Indexed: 01/16/2023] Open
Abstract
Most enzyme reactions involve formation and cleavage of covalent bonds, while electrostatic effects, as well as dynamics of the active site and surrounding protein regions, may also be crucial. Accordingly, special computational methods are needed to provide an adequate description, which combine quantum mechanics for the reactive region with molecular mechanics and molecular dynamics describing the environment and dynamic effects, respectively. In this review we intend to give an overview to non-specialists on various enzyme models as well as established computational methods and describe applications to some specific cases. For the treatment of various enzyme mechanisms, special approaches are often needed to obtain results, which adequately refer to experimental data. As a result of the spectacular progress in the last two decades, most enzyme reactions can be quite precisely treated by various computational methods.
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25
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Sanders BC, Patra AK, Harrop TC. Synthesis, properties, and reactivity of a series of non-heme {FeNO}7/8 complexes: Implications for Fe-nitroxyl coordination. J Inorg Biochem 2013; 118:115-27. [DOI: 10.1016/j.jinorgbio.2012.08.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/17/2012] [Accepted: 08/18/2012] [Indexed: 10/27/2022]
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26
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Evaluation of structural features in fungal cytochromes P450 predicted to rule catalytic diversification. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:205-20. [DOI: 10.1016/j.bbapap.2012.09.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/17/2012] [Accepted: 09/18/2012] [Indexed: 01/11/2023]
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27
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Sanders BC, Rhine MA, Harrop TC. Properties of {FeNO}8 and {CoNO}9 Metal Nitrosyls in Relation to Nitroxyl Coordination Chemistry. MOLECULAR DESIGN IN INORGANIC BIOCHEMISTRY 2013. [DOI: 10.1007/430_2012_87] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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28
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Lehnert N, Scheidt WR, Wolf MW. Structure and Bonding in Heme–Nitrosyl Complexes and Implications for Biology. NITROSYL COMPLEXES IN INORGANIC CHEMISTRY, BIOCHEMISTRY AND MEDICINE II 2013. [DOI: 10.1007/430_2013_92] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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29
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Shoun H, Fushinobu S, Jiang L, Kim SW, Wakagi T. Fungal denitrification and nitric oxide reductase cytochrome P450nor. Philos Trans R Soc Lond B Biol Sci 2012; 367:1186-94. [PMID: 22451104 DOI: 10.1098/rstb.2011.0335] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have shown that many fungi (eukaryotes) exhibit distinct denitrifying activities, although occurrence of denitrification was previously thought to be restricted to bacteria (prokaryotes), and have characterized the fungal denitrification system. It comprises NirK (copper-containing nitrite reductase) and P450nor (a cytochrome P450 nitric oxide (NO) reductase (Nor)) to reduce nitrite to nitrous oxide (N(2)O). The system is localized in mitochondria functioning during anaerobic respiration. Some fungal systems further contain and use dissimilatory and assimilatory nitrate reductases to denitrify nitrate. Phylogenetic analysis of nirK genes showed that the fungal-denitrifying system has the same ancestor as the bacterial counterpart and suggested a possibility of its proto-mitochondrial origin. By contrast, fungi that have acquired a P450 from bacteria by horizontal transfer of the gene, modulated its function to give a Nor activity replacing the original Nor with P450nor. P450nor receives electrons directly from nicotinamide adenine dinucleotide to reduce NO to N(2)O. The mechanism of this unprecedented electron transfer has been extensively studied and thoroughly elucidated. Fungal denitrification is often accompanied by a unique phenomenon, co-denitrification, in which a hybrid N(2) or N(2)O species is formed upon the combination of nitrogen atoms of nitrite with a nitrogen donor (amines and imines). Possible involvement of NirK and P450nor is suggested.
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Affiliation(s)
- Hirofumi Shoun
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
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30
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Krámos B, Menyhárd DK, Oláh J. Direct hydride shift mechanism and stereoselectivity of P450nor confirmed by QM/MM calculations. J Phys Chem B 2012; 116:872-85. [PMID: 22148861 DOI: 10.1021/jp2080918] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Nitric oxide reductase (P450(nor)) found in Fusarium oxysporum catalyzes the reduction of nitric oxide to N(2)O in a multistep process. The reducing agent, NADH, is bound in the distal pocket of the enzyme, and direct hydride transfer occurs from NADH to the nitric oxide bound heme enzyme, forming intermediate I. Here we studied the possibility of hydride transfer from NADH to both the nitrogen and oxygen of the heme-bound nitric oxide, using quantum chemical and combined quantum mechanics/molecular mechanics (QM/MM) calculations, on two different protein models, representing both possible stereochemistries, a syn- and an anti-NADH arrangement. All calculations clearly favor hydride transfer to the nitrogen of nitric oxide, and the QM-only barrier and kinetic isotope effects are good agreement with the experimental values of intermediate I formation. We obtained higher barriers in the QM/MM calculations for both pathways, but hydride transfer to the nitrogen of nitric oxide is still clearly favored. The barriers obtained for the syn, Pro-R conformation of NADH are lower and show significantly less variation than the barriers obtained in the case of anti conformation. The effect of basis set and wide range of functionals on the obtained results are also discussed.
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Affiliation(s)
- Balázs Krámos
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary
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Patra AK, Dube KS, Sanders BC, Papaefthymiou GC, Conradie J, Ghosh A, Harrop TC. A thermally stable {FeNO}8complex: properties and biological reactivity of reduced MNO systems. Chem Sci 2012. [DOI: 10.1039/c1sc00582k] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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Doctorovich F, Bikiel D, Pellegrino J, Suárez SA, Larsen A, Martí MA. Nitroxyl (azanone) trapping by metalloporphyrins. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2011.04.012] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Riplinger C, Neese F. The reaction mechanism of Cytochrome P450 NO reductase: a detailed quantum mechanics/molecular mechanics study. Chemphyschem 2011; 12:3192-203. [PMID: 22095732 DOI: 10.1002/cphc.201100523] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 10/10/2011] [Indexed: 11/09/2022]
Abstract
A detailed QM/MM study on the reaction mechanism of Cytochrome P450 NO reductase is reported. Two reaction pathways connecting the two well-characterized intermediates as well as two putative intermediates that represent the unknown third intermediate are explored, with emphasis on the unusual direct reduction of the enzymatic active site by the cofactor NADH. Activation barriers and kinetic isotope effect are calculated and reveal that reduction of the NO-bound species occurs in form of a hydride ion transfer. Furthermore, the impact of different hydrogen bonds in the active site to binding and reactivity of NADH is explored. The calculated kinetic and thermodynamic properties for both modelled pathways are used for the kinetic simulation of the entire reaction course. It is thus shown that the unknown key intermediate is the singlet diradical Fe(III)-NHOH(⋅). It is also found that the mechanism of the N-N bond formation is spin-recoupling, which is only possible due to the diradical character of the key intermediate.
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Affiliation(s)
- Christoph Riplinger
- MPI for Bioinorganic Chemistry, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
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Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase. Proc Natl Acad Sci U S A 2011; 108:18926-31. [PMID: 22084064 DOI: 10.1073/pnas.1111488108] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Quercetin dioxygenase (QDO) catalyzes the oxidation of the flavonol quercetin with dioxygen, cleaving the central heterocyclic ring and releasing CO. The QDO from Bacillus subtilis is unusual in that it has been shown to be active with several divalent metal cofactors such as Fe, Mn, and Co. Previous comparison of the catalytic activities suggest that Mn(II) is the preferred cofactor for this enzyme. We herein report the unprecedented substitution of nitrosyl hydride (HNO) for dioxygen in the activity of Mn-QDO, resulting in the incorporation of both N and O atoms into the product. Turnover is demonstrated by consumption of quercetin and other related substrates under anaerobic conditions in the presence of HNO-releasing compounds and the enzyme. As with dioxygenase activity, a nonenzymatic base-catalyzed reaction of quercetin with HNO is observed above pH 7, but no enhancement of this basal reactivity is found upon addition of divalent metal salts. Unique and regioselective N-containing products ((14)N/(15)N) have been characterized by MS analysis for both the enzymatic and nonenzymatic reactions. Of the several metallo-QDO enzymes examined for nitroxygenase activity under anaerobic condition, only the Mn(II) is active; the Fe(II) and Co(II) substituted enzymes show little or no activity. This result represents an enzymatic catalysis which we denote nitroxygenase activity; the unique reactivity of the Mn-QDO suggests a metal-mediated electron transfer mechanism rather than metal activation of the substrate's inherent base-catalyzed reactivity.
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Kumar MR, Fukuto JM, Miranda KM, Farmer PJ. Reactions of HNO with heme proteins: new routes to HNO-heme complexes and insight into physiological effects. Inorg Chem 2010; 49:6283-92. [PMID: 20666387 DOI: 10.1021/ic902319d] [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
The formation and interconversion of nitrogen oxides has been of interest in numerous contexts for decades. Early studies focused on gas-phase reactions, particularly with regard to industrial and atmospheric environments, and on nitrogen fixation. Additionally, investigation of the coordination chemistry of nitric oxide (NO) with hemoglobin dates back nearly a century. With the discovery in the early 1980s that NO is biosynthesized as a molecular signaling agent, the literature has been focused on the biological effects of nitrogen oxides, but the original concerns remain relevant. For instance, hemoglobin has long been known to react with nitrite, but this reductase activity has recently been considered to be important to produce NO under hypoxic conditions. The association of nitrosyl hydride (HNO; also commonly referred to as nitroxyl) with heme proteins can also produce NO by reductive nitrosylation. Furthermore, HNO is considered to be an intermediate in bacterial denitrification, but conclusive identification has been elusive. The authors of this article have approached the bioinorganic chemistry of HNO from different perspectives, which have converged because heme proteins are important biological targets of HNO.
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Affiliation(s)
- Murugaeson R Kumar
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76706, USA
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Goodrich LE, Paulat F, Praneeth VKK, Lehnert N. Electronic Structure of Heme-Nitrosyls and Its Significance for Nitric Oxide Reactivity, Sensing, Transport, and Toxicity in Biological Systems. Inorg Chem 2010; 49:6293-316. [DOI: 10.1021/ic902304a] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Lauren E. Goodrich
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | - Florian Paulat
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | - V. K. K. Praneeth
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | - Nicolai Lehnert
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
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Daiber A, Schildknecht S, Müller J, Kamuf J, Bachschmid MM, Ullrich V. Chemical model systems for cellular nitros(yl)ation reactions. Free Radic Biol Med 2009; 47:458-67. [PMID: 19477267 PMCID: PMC4006669 DOI: 10.1016/j.freeradbiomed.2009.05.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 04/21/2009] [Accepted: 05/18/2009] [Indexed: 01/21/2023]
Abstract
S-nitros(yl)ation belongs to the redox-based posttranslational modifications of proteins but the underlying chemistry is controversial. In contrast to current concepts involving the autoxidation of nitric oxide ((.)NO, nitrogen monoxide), we and others have proposed the formation of peroxynitrite (oxoperoxonitrate (1(-))as an essential intermediate. This requires low cellular fluxes of (.)NO and superoxide (UO2(-)), for which model systems have been introduced. We here propose two new systems for nitros(yl)ation that avoid the shortcomings of previous models. Based on the thermal decomposition of 3-morpholinosydnonimine,equal fluxes of (.)NO and UO2(-) were generated and modulated by the addition of (.)NO donors or Cu,Zn superoxide dismutase. As reactants for S-nitros(yl)ation, NADP+-dependent isocitrate dehydrogenase and glutathione were employed, for which optimal S-nitros(yl)ation was observed at nanomolar fluxes of (.)NO and UO2(-) at a ratio of about 3:1. The previously used reactants phenol and diaminonaphthalene (C- and Nnitrosation)demonstrated potential participation of multiple pathways for nitros(yl)ation. According to our data, neither peroxynitrite nor autoxidation of UNO was as efficient as the 3 (.)NO/1 UO2(-) system in mediating S-nitros(yl)ation. In theory this could lead to an elusive nitrosonium (nitrosyl cation)-like species in the first step and to N2O3 in the subsequent reaction. Which of these two species or whether both together will participate in biological S-nitros(yl)ation remains to be elucidated. Finally, we developed several hypothetical scenarios to which the described (.)NO/UO2-flux model could apply, providing conditions that allow either direct electrophilic substitution at a thiolate or S-nitros(yl)ation via transnitrosation from S-nitrosoglutathione.
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Affiliation(s)
- Andreas Daiber
- Second Medical Clinic, Department of Cardiology, Johannes Gutenberg University, 55101 Mainz, Germany.
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Affiliation(s)
- Victor Rosca
- Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
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39
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Purification and functional analysis of fungal nitric oxide reductase cytochrome P450nor. Methods Enzymol 2008. [PMID: 18433626 DOI: 10.1016/s0076-6879(07)37007-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2023]
Abstract
Cytochrome P450nor (P450nor) is a nitric oxide (NO) reductase involved in fungal denitrification. Denitrification is a biological process in which nitrate or nitrite is reduced to gaseous nitrogen, the reverse reaction of nitrogen fixation. It therefore plays an important role in maintaining global environmental homeostasis. The involvement of P450nor in fungal denitrification indicates that denitrification not only occurs in prokaryotic bacteria, but also in eukaryotic fungi. In addition, the reduction of NO to nitrous oxide catalyzed by P450nor has added new insight into the function of cytochrome P450s, which are usually monooxygenases. Currently, five isozymes of P450nor have been isolated from the subdivisions of eumycota, and studies on the function and structure of P450nor have provided important information for both molecular mechanisms of P450 reactions and wastewater treatment. This chapter describes the screening of NO reductase activities, cloning, purification, and functional analysis of P450nor.
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de Groot MT, Merkx M, Koper MT. Bioinspired electrocatalytic reduction of nitric oxide by immobilized heme groups. CR CHIM 2007. [DOI: 10.1016/j.crci.2006.11.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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41
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Linder DP, Rodgers KR. Computational modeling of factors that modulate the unique FeNO bonding in {FeNO}(6) heme-thiolate model complexes. J Biol Inorg Chem 2007; 12:721-31. [PMID: 17356871 DOI: 10.1007/s00775-007-0223-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Accepted: 02/09/2007] [Indexed: 10/23/2022]
Abstract
A density functional theory account of the changes in FeNO bonding that occur in response to both bonded and nonbonded structural perturbations is reported for a series of {FeNO}(6) heme-thiolate model complexes. Using [Fe(porphine)(SCH(3))NO] as the reference complex, we constructed models to mimic equatorial (cis), distal, and proximal influences of protein environments. Overall, the results from these calculations reveal that the Fe-NO and N-O bond strengths change in the same direction upon variations in structure and environment. These bonding changes are manifested in unique direct correlations between the Fe-NO and N-O vibrational frequencies and bond lengths, as evidenced by their positive slopes (slopes of the familiar inverse or backbonding correlations are negative). The electronic origin of the direct correlations appears to derive from the electron density distribution in high-energy molecular orbitals. This variability modulates the FeNO antibonding character throughout the triatomic FeNO moiety. The results of this study suggest that the stabilities and reactivities of {FeNO}(6) centers in heme-thiolate enzymes can be modulated over a significant range through a variety of bonded and nonbonded means.
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Affiliation(s)
- Douglas P Linder
- Department of Chemistry, Biochemistry, and Molecular Biology, North Dakota State University, Fargo, ND 58105-5516, USA
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Pérez T, Garcia-Montiel D, Trumbore S, Tyler S, de Camargo P, Moreira M, Piccolo M, Cerri C. Nitrous oxide nitrification and denitrification 15N enrichment factors from Amazon forest soils. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2006; 16:2153-67. [PMID: 17205894 DOI: 10.1890/1051-0761(2006)016[2153:nonadn]2.0.co;2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The isotopic signatures of 15N and 18O in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes in constraining the global N2O budget. Determining the reasons for spatial and temporal variations in isotope signatures requires that we know the isotope enrichment factors for nitrification and denitrification, the two processes that produce N2O in soils. We have devised a method for measuring these enrichment factors using soil incubation experiments and report results from this method for three rain forest soils collected in the Brazilian Amazon: soil with differing sand and clay content from the Tapajos National Forest (TNF) near Santarém, Pará, and Nova Vida Farm, Rondônia. The 15N enrichment factors for nitrification and denitrification differ with soil texture and site: -111 per thousand +/- 12 per thousand and -31 per thousand +/- 11 per thousand for a clay-rich Oxisol (TNF), -102 per thousand +/- 5 per thousand and -45 per thousand +/- 5 per thousand for a sandier Ultisol (TNF), and -10.4 per thousand +/- 3.5 per thousand (enrichment factor for denitrification) for another Ultisol (Nova Vida) soil, respectively. We also show that the isotopomer site preference (delta15Nalpha - delta15Nbeta, where alpha indicates the central nitrogen atom and beta the terminal nitrogen atom in N2O) may allow differentiation between processes of production and consumption of N2O and can potentially be used to determine the contributions of nitrification and denitrification. The site preferences for nitrification and denitrification from the TNF-Ultisol incubated soils are: 4.2 per thousand +/- 8.4 per thousand and 31.6 per thousand +/- 8.1 per thousand, respectively. Thus, nitrifying and denitrifying bacteria populations under the conditions of our study exhibit significantly different 15N site preference fingerprints. Our data set strongly suggests that N2O isotopomers can be used in concert with traditional N2O stable isotope measurements as constraints to differentiate microbial N2O processes in soil and will contribute to interpretations of the isotopic site preference N2O values found in the free troposphere.
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Affiliation(s)
- Tibisay Pérez
- Atmospheric Chemistry Laboratory, Instituto Venezolano de Investigaciones Científicas (IVIC) Apartado 21827, Caracas 1020-A, Venezuela.
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Menyhárd DK, Keseru GM. Binding mode analysis of the NADH cofactor in nitric oxide reductase: a theoretical study. J Mol Graph Model 2006; 25:363-72. [PMID: 16542862 DOI: 10.1016/j.jmgm.2006.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2004] [Revised: 10/10/2005] [Accepted: 02/13/2006] [Indexed: 11/24/2022]
Abstract
Nitric oxide reductase (Nor), a member of the cytochrome P450 superfamily, takes part in the denitrification process of fungi by reducing NO to N(2)O. Evidence indicates that Nor binds NADH, source of the reducing equivalents of the reaction, within its large hydrophilic ligand binding cavity on the distal side of heme and receives electrons directly from the cofactor. Here we present a binding mode analysis of the structure of the Nor-NO-NADH complex, performed in three steps. The NADH cofactor was first docked into the enzyme interior using the Monte Carlo multiple minimum algorithm, refined by low-mode conformational search and the final arrangement was obtained in a 5ns NPT molecular dynamics simulation. The NADH cofactor, in our results, is positioned--by Arg174, Lys291, Asp393 and several water molecules--within reactive distance of the NO binding spot suggesting a direct hydride shift mechanism between the two. The catalytically required water molecule is captured by NADH and the cofactor not only retains the suggested H-bonded proton transfer pathway between the active site and the solvent, but provides structural restraint for its members. We also found that direct interaction is formed between the cofactor and propionate A of the heme group, which flips from the proximal to the distal side of the heme plane in order to become an H-bonding partner of NADH. The role of Arg64 and Glu71 was suggested to be fixing the residues of the translocated helix B' to their new position.
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Affiliation(s)
- Dóra K Menyhárd
- Department of Chemical Information Technology, Budapest University of Technology and Economics, Gellért Tér 4., H-1111 Budapest, Hungary.
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Boccini F, Domazou AS, Herold S. Pulse Radiolysis Studies of the Reactions of CO3•- and NO2• with Nitrosyl(II)myoglobin and Nitrosyl(II)hemoglobin. J Phys Chem A 2006; 110:3927-32. [PMID: 16539414 DOI: 10.1021/jp056452l] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reactions of carbonate radical anion [CO3*-, systematic name: trioxidocarbonate*1-] with nitrosyl(II)hemoglobin (HbFe(II)NO) and nitrosyl(II)myoglobin (MbFe(II)NO) were studied by pulse radiolysis in N2O-saturated 0.25 M sodium bicarbonate solutions at pH 10.0 and room temperature. The reactions proceed in two steps: outer-sphere oxidation of the nitrosyliron(II) proteins to their corresponding nitrosyliron(III) forms and subsequent dissociation of NO*. The second-order rate constants measured for the first reaction steps were (4.3 +/- 0.2) x 10(8) and (1.5 +/- 0.3) x 10(8) M(-1) s(-1), for MbFe(II)NO and HbFe(II)NO, respectively. The reactions between nitrogen dioxide and MbFe(II)NO or HbFe(II)NO were studied by pulse radiolysis in N2O-saturated 0.1 M phosphate buffer pH 7.4 containing 5 mM nitrite. Also for the reactions of this oxidant with the nitrosyliron(II) forms of Mb and Hb a two-step reaction was observed: oxidation of the iron was followed by dissociation of NO*. The second-order rate constants measured for the first reaction steps were (2.9 +/- 0.3) x 10(7) and (1.8 +/- 0.3) x 10(7) M(-1) s(-1), for MbFe(II)NO and HbFe(II)NO, respectively. Both radicals appear to be able to oxidize the iron(II) centers of the proteins directly. Only for the reactions with HbFe(II)NO it cannot be excluded that, in a parallel reaction, CO3*- and NO2* first react with amino acid(s) of the globin, which then oxidize the nitrosyliron(II) center.
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Affiliation(s)
- Francesca Boccini
- Laboratorium für Anorganische Chemie, Eidgenössische Technische Hochschule, ETH Hönggerberg, CH-8093 Zürich, Switzerland
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Hartree–Fock and density functional theory calculations for the reaction mechanism of nitric oxide reductase cytochrome P450nor from Fusarium oxysporum. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.theochem.2005.06.040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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de Groot MT, Merkx M, Koper MTM. Heme Release in Myoglobin−DDAB Films and Its Role in Electrochemical NO Reduction. J Am Chem Soc 2005; 127:16224-32. [PMID: 16287313 DOI: 10.1021/ja0546572] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrochemical nitric oxide (NO) reduction by heme groups incorporated in films of didodecyldimethylammonium bromide (DDAB) on pyrolitic graphite was investigated. It is shown that DDAB most likely induces the release of the heme group from myoglobin and therefore myoglobin-DDAB and heme-DDAB films give the same voltammetric responses. This is confirmed by UV/vis spectroscopy showing a clear shift in the Soret band of myoglobin in a DDAB solution. The electrochemical NO reduction on a heme-DDAB film at different pH values reveals the presence of pH-dependent and pH-independent NO reduction pathways. The selectivity of these pathways is probed by combining the rotating ring-disk electrode technique with online electrochemical mass spectroscopy showing that the product of the pH-independent pathway is N2O and the product of the pH-dependent pathway is NH2OH. The preference for one or the other pathway seems to depend on whether a proton or a NO molecule is transferred to a Fe(II)-NO- reaction intermediate and is influenced by pH, NO concentration, and potential.
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Affiliation(s)
- Matheus T de Groot
- Laboratory of Inorganic Chemistry and Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Michel E, Nauser T, Sutter B, Bounds PL, Koppenol WH. Kinetics properties of Cu,Zn-superoxide dismutase as a function of metal content. Arch Biochem Biophys 2005; 439:234-40. [PMID: 15978540 DOI: 10.1016/j.abb.2005.05.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Revised: 05/11/2005] [Accepted: 05/13/2005] [Indexed: 10/25/2022]
Abstract
The kinetics of bovine Cu,Zn superoxide dismutase were studied by pulse radiolysis. To ensure the absence of catalytically active free copper, commercially obtained holo-superoxide dismutase was demetallated, and the apo-superoxide dismutase concentrations were determined by isothermal titration calorimetry prior to reconstitution with defined amounts of copper and zinc. The catalytic rate constant was determined as a function of ionic strength over the range of 4-154 mM, and of the copper and zinc content. The catalytic rate constant increases with ionic strength up to (1.5 +/- 0.2) x 10(9) M(-1) s(-1) at an ionic strength of 15 mM, and then decreases. At pH 7 and 50 mM ionic strength, k = (1.2 +/- 0.2) x 10(9) M(-1) s(-1), and at a physiologically relevant ionic strength of 150 mM, it is (0.7 +/- 0.1) x 10 (9) M(-1) s(-1). The effect of ionic strength is ascribed to the inhomogeneous electric field generated by the surface charges of superoxide dismutase. The value of the catalytic rate constant at 50 mM is ca. 2-fold smaller than earlier values reported in the literature. The relationship between copper content and the catalytic rate constant shows that addition of more than a stoichiometric amount of copper cannot be masked efficiently by EDTA. The possibility exists that earlier reported values were based on experiments contaminated with trace amounts of copper.
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Affiliation(s)
- Erich Michel
- Inorganic Institute, Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland
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49
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de Groot MT, Merkx M, Wonders AH, Koper MTM. Electrochemical Reduction of NO by Hemin Adsorbed at Pyrolitic Graphite. J Am Chem Soc 2005; 127:7579-86. [PMID: 15898809 DOI: 10.1021/ja051151a] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanism of the electrochemical reduction of nitric oxide (NO) by hemin adsorbed at pyrolitic graphite was investigated. The selectivity of NO reduction was probed by combining the rotating ring disk electrode (RRDE) technique with a newly developed technique called on-line electrochemical mass spectroscopy (OLEMS). These techniques show that NO reduction by adsorbed heme groups results in production of hydroxylamine (NH(2)OH) with almost 100% selectivity at low potentials. Small amounts of nitrous oxide (N(2)O) were only observed at higher potentials. The rate-determining step in NO reduction most likely consists of an electrochemical equilibrium involving a proton transfer, as can be derived from the Tafel slope value of 62 mV/dec and the pH dependence of -42 mV/pH. The almost 100% selectivity toward NH(2)OH distinguishes this system both from NO reduction on bare metal electrodes, which often yields NH(3), and from biological NO reduction in cytochrome P450nor, which yields N(2)O exclusively.
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Affiliation(s)
- Matheus T de Groot
- Laboratory of Inorganic Chemistry and Catalysis, Schuit Institute of Catalysis, Netherlands
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50
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Denisov IG, Makris TM, Sligar SG, Schlichting I. Structure and Chemistry of Cytochrome P450. Chem Rev 2005; 105:2253-77. [PMID: 15941214 DOI: 10.1021/cr0307143] [Citation(s) in RCA: 1512] [Impact Index Per Article: 79.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ilia G Denisov
- Department of Biochemistry, Center for Biophysics and Computational Biology, University of Illinois, Urbana-Champaign, 61801, USA
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