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Chen J, Tang Q, Wang Y, Xu M, Sun S, Zhang J, Wu R, Yue X, Li X, Chen Q, Liang X. Ultrasound-Induced Piezocatalysis Triggered NO Generation for Enhanced Hypoxic Tumor Therapy. ACS APPLIED MATERIALS & INTERFACES 2023; 15:15220-15234. [PMID: 36922152 DOI: 10.1021/acsami.3c00603] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Conventional NO gas generation based on l-arginine (l-Arg) is usually dependent on H2O2 and O2, both of which are very limited within the tumor microenvironment, thus greatly limiting l-Arg's therapeutic effect. Herein, a novel nanoplatform for efficiently triggering NO production based on ultrasound-induced piezocatalysis was developed, which was fabricated by coating amphiphilic poly-l-arginine (DSPE-PEG2000-Arg, DPA) on the piezoelectric material of barium titanate (BTO). The resulting BTO@DPA nanoparticles can efficiently generate H2O2, 1O2, and O2 via ultrasound-induced piezocatalysis based on BTO and oxidize the surface arginine to produce NO, which can even further interact with the reactive oxygen species (ROS) to produce more reactive peroxynitrite, thus inducing serious tumor cell apoptosis both in hypoxia and normoxia. After intravenous injection, BTO@DPA accumulated well at the tumor tissue at 4 h postinjection; later, ultrasound irradiation on the tumor not only achieved the best tumor inhibition rate of ∼70% but also completely inhibited tumor metastasis to the lungs via the alleviation of tumor hypoxia. Such a strategy was not dependent on the tumor microenvironment and can be well controlled by ultrasound irradiation, providing a simple and efficient therapy paradigm for hypoxic tumor.
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Affiliation(s)
- Jing Chen
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Qingshuang Tang
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Yuan Wang
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Menghong Xu
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Suhui Sun
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Jinxia Zhang
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Ruiqi Wu
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
| | - Xiuli Yue
- School of Environment, Harbin Institute of Technology, Harbin, 150090 China
| | - Xiaoda Li
- Medical Isotopes Research Center and Department of Radiation Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Qingfeng Chen
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore 138673, Singapore
| | - Xiaolong Liang
- Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
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2
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Mondal P, Ishigami I, Yeh SR, Wijeratne GB. The Role of Heme Peroxo Oxidants in the Rational Mechanistic Modeling of Nitric Oxide Synthase: Characterization of Key Intermediates and Elucidation of the Mechanism. Angew Chem Int Ed Engl 2022; 61:e202211521. [PMID: 36169890 PMCID: PMC9675724 DOI: 10.1002/anie.202211521] [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: 08/04/2022] [Indexed: 11/08/2022]
Abstract
Mammalian nitric oxide synthase (NOS) mediates the two-step O2 -dependent oxidative degradation of arginine, and has been linked to a medley of disease situations in humans. Nonetheless, its exact mechanism of action still remains unclear. This work presents the first NOS model system where biologically proposed heme superoxo and peroxo intermediates are assessed as active oxidants against oxime substrates. Markedly, heme peroxo intermediates engaged in a bioinspired oxime oxidation reaction pathway, converting oximes to ketones and nitroxyl anions (NO- ). Detailed thermodynamic, kinetic, and mechanistic interrogations all evince a rate-limiting step primarily driven by the nucleophilicity of the heme peroxo moiety. Coherent with other findings, 18 O and 15 N isotope substitution experiments herein suffice compelling evidence toward a detailed mechanism, which draw close parallels to one of the enzymatic proposals. Intriguingly, recent enzymatic studies also lend credence to these findings, and several relevant reaction intermediates have been observed during NOS turnover.
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Affiliation(s)
- Pritam Mondal
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Izumi Ishigami
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, The Bronx, NY 10461, USA
| | - Syun-Ru Yeh
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, The Bronx, NY 10461, USA
| | - Gayan B Wijeratne
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35205, USA
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3
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Johnson CM, Fast W. On the kinetic mechanism of dimethylarginine dimethylaminohydrolase. Bioorg Med Chem 2022; 66:116816. [PMID: 35598478 DOI: 10.1016/j.bmc.2022.116816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/06/2022] [Accepted: 05/09/2022] [Indexed: 11/28/2022]
Abstract
Dimethylarginine dimethylaminohydrolase (DDAH, EC 3.5.3.18) catalyzes the hydrolysis of asymmetric Nω,Nω-dimethyl-l-arginine (ADMA), an endogenous inhibitor of human nitric oxide synthases. The active-site cysteine residue has been proposed to serve as the catalytic nucleophile, forming an S-alkylthiourea reaction intermediate, and serving as a target for covalent inhibitors. Inhibition can lead to ADMA accumulation and downstream inhibition of nitric oxide production. Prior studies have provided experimental evidence for formation of this covalent adduct but have not characterized it kinetically. Here, rapid quench-flow is used with ADMA and the DDAH from Pseudomonas aeruginosa to determine the rate constants for formation (k2 = 17 ± 2 s-1) and decay (k3 = 1.5 ± 0.1 s-1) of the covalent S-alkylthiourea adduct. A minimal kinetic mechanism for DDAH is proposed that supports the kinetic competence of this species as a covalent reaction intermediate and assigns the rate-limiting step in substrate turnover as hydrolysis of this intermediate. This work helps elucidate the different reactivities of S-alkylthiourea intermediates found among the mechanistically diverse pentein superfamily of guanidine-modifying enzymes and provides information useful for inhibitor development.
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Affiliation(s)
- Corey M Johnson
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, TX 78712, USA; Department of Chemistry and Biochemistry, Howard College of Arts and Sciences, Samford University, Birmingham, AL 35229, USA
| | - Walter Fast
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, TX 78712, USA.
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4
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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: 82] [Impact Index Per Article: 27.3] [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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5
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Mondal P, Ishigami I, Gérard EF, Lim C, Yeh SR, de Visser SP, Wijeratne GB. Proton-coupled electron transfer reactivities of electronically divergent heme superoxide intermediates: a kinetic, thermodynamic, and theoretical study. Chem Sci 2021; 12:8872-8883. [PMID: 34257888 PMCID: PMC8246096 DOI: 10.1039/d1sc01952j] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 05/26/2021] [Indexed: 01/11/2023] Open
Abstract
Heme superoxides are one of the most versatile metallo-intermediates in biology, and they mediate a vast variety of oxidation and oxygenation reactions involving O2(g). Overall proton-coupled electron transfer (PCET) processes they facilitate may proceed via several different mechanistic pathways, attributes of which are not yet fully understood. Herein we present a detailed investigation into concerted PCET events of a series of geometrically similar, but electronically disparate synthetic heme superoxide mimics, where unprecedented, PCET feasibility-determining electronic effects of the heme center have been identified. These electronic factors firmly modulate both thermodynamic and kinetic parameters that are central to PCET, as supported by our experimental and theoretical observations. Consistently, the most electron-deficient superoxide adduct shows the strongest driving force for PCET, whereas the most electron-rich system remains unreactive. The pivotal role of these findings in understanding significant heme systems in biology, as well as in alternative energy applications is also discussed.
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Affiliation(s)
- Pritam Mondal
- Department of Chemistry, University of Alabama at Birmingham Birmingham AL 35205 USA
| | - Izumi Ishigami
- Department of Physiology and Biophysics, Albert Einstein College of Medicine The Bronx New York 10461 USA
| | - Emilie F Gérard
- Manchester Institute of Biotechnology, Department of Chemical Engineering and Analytical Science, The University of Manchester 131 Princess Street Manchester M1 7DN UK
| | - Chaeeun Lim
- Department of Chemistry, University of Alabama at Birmingham Birmingham AL 35205 USA
| | - Syun-Ru Yeh
- Department of Physiology and Biophysics, Albert Einstein College of Medicine The Bronx New York 10461 USA
| | - Sam P de Visser
- Manchester Institute of Biotechnology, Department of Chemical Engineering and Analytical Science, The University of Manchester 131 Princess Street Manchester M1 7DN UK
| | - Gayan B Wijeratne
- Department of Chemistry, University of Alabama at Birmingham Birmingham AL 35205 USA
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6
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Fang X, Cai S, Wang M, Chen Z, Lu C, Yang H. Photogenerated Holes Mediated Nitric Oxide Production for Hypoxic Tumor Treatment. Angew Chem Int Ed Engl 2021; 60:7046-7050. [PMID: 33368982 DOI: 10.1002/anie.202015082] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/21/2020] [Indexed: 12/28/2022]
Abstract
Nitric oxide (NO) is a gaseous signal molecule with multiple physiological functions, and it also plays a key role in cancer therapy. However, the production of NO which depends on O2 or H2 O2 is limited within the tumor microenvironment, leading to unsatisfactory anticancer effect. Herein, we report a NO-based phototherapeutic strategy mediated by photogenerated holes for hypoxic tumors, which is achieved by irradiation of the poly-L-arginine modified carbon-dots-doped graphitic carbon nitride nanomaterial (ArgCCN). Upon red light irradiation, the photogenerated holes on ArgCCN oxidized water into H2 O2 which subsequently oxidized the arginine residues to produce NO. In vitro and in vivo experiments showed that the high concentration of NO produced by ArgCCN could induce cancer cell apoptosis. The presented phototherapeutic strategy is based on microenvironment-independent photogenerated holes mediated oxidation reaction, paving the way for the development of NO therapeutic strategy.
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Affiliation(s)
- Xiao Fang
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Shuxian Cai
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Min Wang
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Zhaowei Chen
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Chunhua Lu
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Huanghao Yang
- MOE Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350108, P. R. China
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7
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Fang X, Cai S, Wang M, Chen Z, Lu C, Yang H. Photogenerated Holes Mediated Nitric Oxide Production for Hypoxic Tumor Treatment. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202015082] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Xiao Fang
- MOE Key Laboratory for Analytical Science of Food Safety and Biology Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety State Key Laboratory of Photocatalysis on Energy and Environment College of Chemistry Fuzhou University Fuzhou 350108 P. R. China
| | - Shuxian Cai
- MOE Key Laboratory for Analytical Science of Food Safety and Biology Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety State Key Laboratory of Photocatalysis on Energy and Environment College of Chemistry Fuzhou University Fuzhou 350108 P. R. China
| | - Min Wang
- MOE Key Laboratory for Analytical Science of Food Safety and Biology Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety State Key Laboratory of Photocatalysis on Energy and Environment College of Chemistry Fuzhou University Fuzhou 350108 P. R. China
| | - Zhaowei Chen
- MOE Key Laboratory for Analytical Science of Food Safety and Biology Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety State Key Laboratory of Photocatalysis on Energy and Environment College of Chemistry Fuzhou University Fuzhou 350108 P. R. China
| | - Chunhua Lu
- MOE Key Laboratory for Analytical Science of Food Safety and Biology Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety State Key Laboratory of Photocatalysis on Energy and Environment College of Chemistry Fuzhou University Fuzhou 350108 P. R. China
| | - Huanghao Yang
- MOE Key Laboratory for Analytical Science of Food Safety and Biology Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety State Key Laboratory of Photocatalysis on Energy and Environment College of Chemistry Fuzhou University Fuzhou 350108 P. R. China
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8
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Sacramento JJD, Goldberg DP. Oxidation of an indole substrate by porphyrin iron(iii) superoxide: relevance to indoleamine and tryptophan 2,3-dioxygenases. Chem Commun (Camb) 2020; 56:3089-3092. [PMID: 32052805 PMCID: PMC7065957 DOI: 10.1039/c9cc10019a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Reaction of FeIII(O2˙-)(TPP) with 2,3-dimethylindole at -40 °C gives the ring-opened, dioxygenated N-(2-acetyl-phenyl)-acetamide product. The reaction was monitored in situ by low-temperature UV-vis and 1H NMR spectroscopies. This work demonstrates that a discrete iron(iii)(superoxo) porphyrin is competent to carry out indole oxidation, as proposed for the tryptophan and indoleamine 2,3-dioxygenases.
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Affiliation(s)
- Jireh Joy D Sacramento
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
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9
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Sacramento JJD, Goldberg DP. The hydrogen atom transfer reactivity of a porphyrinoid cobalt superoxide complex. Chem Commun (Camb) 2019; 55:913-916. [PMID: 30608073 DOI: 10.1039/c8cc08453j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The H-atom transfer (HAT) reactivity of a corrolazine cobalt superoxide with weak O-H and N-H substrates has been demonstrated. Kinetic analysis shows relatively fast rates of HAT with diphenylhydrazine (DPH). A kinetic isotope effect (KIE) and Eyring activation parameters are consistent with an HAT mechanism.
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Affiliation(s)
- Jireh Joy D Sacramento
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
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10
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A gentle introduction to gasotransmitters with special reference to nitric oxide: biological and chemical implications. REV INORG CHEM 2018. [DOI: 10.1515/revic-2018-0011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
AbstractNitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) are gaseous molecules of major impact in biology. Despite their toxicity, these molecules have profound effects on mammalian physiology and major implications in therapeutics. At tiny concentrations in human biology, they play key signaling and regulatory functions and hence are now labeled as “gasotransmitters.” In this literature survey, an introduction to gasotransmitters in relevance with NO, CO and H2S has been primarily focused. A special attention has been given to the conjoint physiological, pathophysiological and therapeutic aspects of NO in this work. In addition to the aforementioned elements of the investigation being reported, this report gives a detailed account of some of the recent advancements covering the NO release from both the nitro as well as nitroso compounds. The importance of the metallic center on the eve of producing the reduction center on NO and to develop photolabile properties have been elaborated within the effect of a few examples of metallic centers. Also, theoretical investigations that have been reported in the recent past and some other current theories pertaining to NO chemistry have been enlightened in this review. From the overall study, it is eminent that a number of facts are yet to be explored in context with NO for deeper mechanistic insights, model design for these molecules, other key roles and the search to find the best fit formalism in theoretical chemistry.
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11
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Adam SM, Wijeratne GB, Rogler PJ, Diaz DE, Quist DA, Liu JJ, Karlin KD. Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function. Chem Rev 2018; 118:10840-11022. [PMID: 30372042 PMCID: PMC6360144 DOI: 10.1021/acs.chemrev.8b00074] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.
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Affiliation(s)
- Suzanne M. Adam
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Gayan B. Wijeratne
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Patrick J. Rogler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Daniel E. Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jeffrey J. Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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12
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Shamovsky I, Belfield G, Lewis R, Narjes F, Ripa L, Tyrchan C, Öberg L, Sjö P. Theoretical studies of the second step of the nitric oxide synthase reaction: Electron tunneling prevents uncoupling. J Inorg Biochem 2018; 181:28-40. [PMID: 29407906 DOI: 10.1016/j.jinorgbio.2018.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/18/2017] [Accepted: 01/08/2018] [Indexed: 12/27/2022]
Abstract
Nitric oxide (NO·) is a messenger molecule with diverse physiological roles including host defense, neurotransmission and vascular function. The synthesis of NO· from l-arginine is catalyzed by NO-synthases and occurs in two steps through the intermediary Nω-hydroxy-l-arginine (NHA). In both steps the P450-like reaction cycle is coupled with the redox cycle of the cofactor tetrahydrobiopterin (H4B). The mechanism of the second step is studied by Density Functional Theory calculations to ascertain the canonical sequence of proton and electron transfer (PT and ET) events. The proposed mechanism is controlled by the interplay of two electron donors, H4B and NHA. Consistent with experimental data, the catalytic cycle proceeds through the ferric-hydroperoxide complex (Cpd 0) and the following aqua-ferriheme resting state, and involves interim partial oxidation of H4B. The mechanism starts with formation of Cpd 0 from the ferrous-dioxy reactant complex by PT from the C-ring heme propionate coupled with hole transfer to H4B through the highest occupied π-orbital of NHA as a bridge. This enables PT from NHA+· to the proximal oxygen leading to the shallow ferriheme-H2O2 oxidant. Subsequent Fenton-like peroxide bond cleavage triggered by ET from the NHA-derived iminoxy-radical leads to the protonated Cpd II diradicaloid singlet stabilized by spin delocalization in H4B, and the closed-shell coordination complex of HO- with iminoxy-cation. The complex is converted to the transient C-adduct, which releases intended products upon PT to the ferriheme-HO- complex coupled with ET to the H4B+·. Deferred ET from the substrate or undue ET from/to the cofactor leads to side products.
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Affiliation(s)
- Igor Shamovsky
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden.
| | - Graham Belfield
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Richard Lewis
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Frank Narjes
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Lena Ripa
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Christian Tyrchan
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Lisa Öberg
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Peter Sjö
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
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13
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Silverman RB. Design and Mechanism of GABA Aminotransferase Inactivators. Treatments for Epilepsies and Addictions. Chem Rev 2018; 118:4037-4070. [PMID: 29569907 DOI: 10.1021/acs.chemrev.8b00009] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
When the brain concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) diminishes below a threshold level, the excess neuronal excitation can lead to convulsions. This imbalance in neurotransmission can be corrected by inhibition of the enzyme γ-aminobutyric acid aminotransferase (GABA-AT), which catalyzes the conversion of GABA to the excitatory neurotransmitter l-glutamic acid. It also has been found that raising GABA levels can antagonize the rapid elevation and release of dopamine in the nucleus accumbens, which is responsible for the reward response in addiction. Therefore, the design of new inhibitors of GABA-AT, which increases brain GABA levels, is an important approach to new treatments for epilepsy and addiction. This review summarizes findings over the last 40 or so years of mechanism-based inactivators (unreactive compounds that require the target enzyme to catalyze their conversion to the inactivating species, which inactivate the enzyme prior to their release) of GABA-AT with emphasis on their catalytic mechanisms of inactivation, presented according to organic chemical mechanism, with minimal pharmacology, except where important for activity in epilepsy and addiction. Patents, abstracts, and conference proceedings are not covered in this review. The inactivation mechanisms described here can be applied to the inactivations of a wide variety of unrelated enzymes.
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Affiliation(s)
- Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , United States
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14
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Tang W, Li H, Poulos TL, Silverman RB. Mechanistic studies of inactivation of inducible nitric oxide synthase by amidines. Biochemistry 2015; 54:2530-8. [PMID: 25811913 DOI: 10.1021/acs.biochem.5b00135] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Nitric oxide synthase (NOS) catalyzes the conversion of L-arginine to L-citrulline and nitric oxide. N(5)-(1-Iminoethyl)-L-ornithine (L-NIO), an amidine-containing molecule, is a natural product known to be an inactivator of inducible NOS (iNOS). Because of the presence of the amidine methyl group in place of the guanidine amino group of substrate L-arginine, the active site heme peroxy intermediate sometimes cannot be protonated, thereby preventing its conversion to the heme oxo intermediate; instead, a heme oxygenase-type mechanism occurs, leading to conversion of the heme to biliverdin. This might be a new and general inactivation mechanism for heme-containing enzymes. In the studies described here, we attempted to provide support for amidines as substrates and inactivators of iNOS by the design and synthesis of amidine analogues of L-NIO having groups other than the amidine methyl group. No nitric oxide- or enzyme-catalyzed products could be detected by incubation of these amidines with iNOS. Although none of the L-NIO analogues acted as substrates, they all inhibited iNOS; increased inhibitory potency correlated with decreased substituent size. Computer modeling and molecular dynamics simulations were run on 10 and 11 to rationalize why these compounds do not act as substrates. Unlike the methyl amidine (L-NIO), the other alkyl groups block binding of O2 at the heme iron. Compounds 8, 9, and 11 were inactivators; however, no heme was lost, and no biliverdin was formed. No kinetic isotope effect on inactivation was observed with perdeuterated ethyl 8. A small amount of dimer disruption occurred with these inactivators, although the amount would not account for complete enzyme inactivation. The L-NIO analogues inactivate iNOS by a yet unknown mechanism; however, it is different from that of L-NIO, and the inactivation mechanism previously reported for L-NIO appears to be unique to methyl amidines.
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Affiliation(s)
- Wei Tang
- †Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- ‡Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Thomas L Poulos
- ‡Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Richard B Silverman
- †Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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15
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Davydov R, Labby KJ, Chobot SE, Lukoyanov DA, Crane BR, Silverman RB, Hoffman BM. Enzymatic and cryoreduction EPR studies of the hydroxylation of methylated N(ω)-hydroxy-L-arginine analogues by nitric oxide synthase from Geobacillus stearothermophilus. Biochemistry 2014; 53:6511-9. [PMID: 25251261 PMCID: PMC4204881 DOI: 10.1021/bi500485z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Nitric
oxide synthase (NOS) catalyzes the conversion of l-arginine
to l-citrulline and NO in a two-step process involving the
intermediate Nω-hydroxy-l-arginine (NHA). It was shown that Cpd I is the oxygenating species
for l-arginine; the hydroperoxo ferric intermediate is the
reactive intermediate with NHA. Methylation of the Nω-OH and Nω-H of NHA significantly inhibits the conversion
of NHA into NO and l-citrulline by mammalian NOS. Kinetic
studies now show that Nω-methylation of NHA has a
qualitatively similar effect on H2O2-dependent
catalysis by bacterial gsNOS. To elucidate the effect of methylating
Nω-hydroxy l-arginine on the properties
and reactivity of the one-electron-reduced oxy-heme center of NOS,
we have applied cryoreduction/annealing/EPR/ENDOR techniques. Measurements
of solvent kinetic isotope effects during 160 K cryoannealing cryoreduced
oxy-gsNOS/NHA confirm the hydroperoxo ferric intermediate as the catalytically
active species of step two. Product analysis for cryoreduced samples
with methylated NHA’s, NHMA, NMOA, and NMMA, annealed to 273
K, show a correlation of yields of l-citrulline with the
intensity of the g 2.26 EPR signal of the peroxo ferric
species trapped at 77 K, which converts to the reactive hydroperoxo
ferric state. There is also a correlation between the yield of l-citrulline in these experiments and kobs for the H2O2-dependent conversion
of the substrates by gsNOS. Correspondingly, no detectable amount
of cyanoornithine, formed when Cpd I is the reactive species, was
found in the samples. Methylation of the NHA guanidinium Nω-OH and Nω-H inhibits the second NO-producing reaction
by favoring protonation of the ferric-peroxo to form unreactive conformers
of the ferric-hydroperoxo state. It is suggested that this is caused
by modification of the distal-pocket hydrogen-bonding network of oxy
gsNOS and introduction of an ordered water molecule that facilitates
delivery of the proton(s) to the one-electron-reduced oxy-heme moiety.
These results illustrate how variations in the properties of the substrate
can modulate the reactivity of a monooxygenase.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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16
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Affiliation(s)
- Thomas L. Poulos
- Departments of Molecular Biology & Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California Irvine, Irvine, California 92697-3900
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17
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Jansen Labby K, Li H, Roman LJ, Martásek P, Poulos TL, Silverman RB. Methylated N(ω)-hydroxy-L-arginine analogues as mechanistic probes for the second step of the nitric oxide synthase-catalyzed reaction. Biochemistry 2013; 52:3062-73. [PMID: 23586781 DOI: 10.1021/bi301571v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Nitric oxide synthase (NOS) catalyzes the conversion of L-arginine to L-citrulline through the intermediate N(ω)-hydroxy-L-arginine (NHA), producing nitric oxide, an important mammalian signaling molecule. Several disease states are associated with improper regulation of nitric oxide production, making NOS a therapeutic target. The first step of the NOS reaction has been well-characterized and is presumed to proceed through a compound I heme species, analogous to the cytochrome P450 mechanism. The second step, however, is enzymatically unprecedented and is thought to occur via a ferric peroxo heme species. To gain insight into the details of this unique second step, we report here the synthesis of NHA analogues bearing guanidinium methyl or ethyl substitutions and their investigation as either inhibitors of or alternate substrates for NOS. Radiolabeling studies reveal that N(ω)-methoxy-L-arginine, an alternative NOS substrate, produces citrulline, nitric oxide, and methanol. On the basis of these results, we propose a mechanism for the second step of NOS catalysis in which a methylated nitric oxide species is released and is further metabolized by NOS. Crystal structures of our NHA analogues bound to nNOS have been determined, revealing the presence of an active site water molecule only in the presence of singly methylated analogues. Bulkier analogues displace this active site water molecule; a different mechanism is proposed in the absence of the water molecule. Our results provide new insights into the steric and stereochemical tolerance of the NOS active site and substrate capabilities of NOS.
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Affiliation(s)
- Kristin Jansen Labby
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
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18
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Santolini J. The molecular mechanism of mammalian NO-synthases: a story of electrons and protons. J Inorg Biochem 2010; 105:127-41. [PMID: 21194610 DOI: 10.1016/j.jinorgbio.2010.10.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/19/2010] [Accepted: 10/22/2010] [Indexed: 02/01/2023]
Abstract
Since its discovery, nitric oxide synthase (NOS), the enzyme responsible for NO biosynthesis in mammals, has been the subject of extensive investigations regarding its catalytic and molecular mechanisms. These studies reveal the high degree of sophistication of NOS functioning and regulation. However, the precise description of the NOS molecular mechanism and in particular of the oxygen activation chemistry is still lacking. The reaction intermediates implicated in NOS catalysis continue to elude identification and the current working paradigm is increasingly contested. Consequently, the last three years has seen the emergence of several competing models. All these models propose the same global reaction scheme consisting of two successive oxidation reactions but they diverge in the details of their reaction sequence. The major discrepancies concern the number, source and characteristics of proton and electron transfer processes. As a result each model proposes distinct reaction pathways with different implied oxidative species. This review aims to examine the different experimental evidence concerning NOS proton and electron transfer events and the role played by the substrates and cofactors in these processes. The resulting discussion should provide a comparative picture of all potential models for the NOS molecular mechanism.
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Affiliation(s)
- Jérôme Santolini
- iBiTec-S; LSOD, C. E. A. Saclay; 91191 Gif-sur-Yvette Cedex, France.
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19
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Nigro AP, Goodin DB. Reaction of N-hydroxyguanidine with the ferrous-oxy state of a heme peroxidase cavity mutant: a model for the reactions of nitric oxide synthase. Arch Biochem Biophys 2010; 500:66-73. [PMID: 20346907 DOI: 10.1016/j.abb.2010.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 03/19/2010] [Accepted: 03/20/2010] [Indexed: 12/01/2022]
Abstract
Yeast cytochrome c peroxidase was used to construct a model for the reactions catalyzed by the second cycle of nitric oxide synthase. The R48A/W191F mutant introduced a binding site for N-hydroxyguanidine near the distal heme face and removed the redox active Trp-191 radical site. Both the R48A and R48A/W191F mutants catalyzed the H2O2 dependent conversion of N-hydroxyguanidine to N-nitrosoguanidine. It is proposed that these reactions proceed by direct one-electron oxidation of NHG by the Fe(+4)O center of either Compound I (Fe(+4)=O, porph+(.)) or Compound ES (Fe(+4)=O, Trp+(.)). R48A/W191F formed a Fe(+2)O2 complex upon photolysis of Fe(+2)CO in the presence of O2, and N-hydroxyguanidine was observed to react with this species to produce products, distinct from N-nitrosoguanidine, that gave a positive Griess reaction for nitrate+nitrite, a positive Berthelot reaction for urea, and no evidence for formation of NO(.). It is proposed that HNO and urea are produced in analogy with reactions of nitric oxide synthase in the pterin-free state.
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Affiliation(s)
- Alycen Pond Nigro
- Department of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA
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20
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Giroud C, Moreau M, Mattioli TA, Balland V, Boucher JL, Xu-Li Y, Stuehr DJ, Santolini J. Role of arginine guanidinium moiety in nitric-oxide synthase mechanism of oxygen activation. J Biol Chem 2009; 285:7233-45. [PMID: 19951943 DOI: 10.1074/jbc.m109.038240] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Nitric-oxide synthases (NOS) are highly regulated heme-thiolate enzymes that catalyze two oxidation reactions that sequentially convert the substrate L-Arg first to N(omega)-hydroxyl-L-arginine and then to L-citrulline and nitric oxide. Despite numerous investigations, the detailed molecular mechanism of NOS remains elusive and debatable. Much of the dispute in the various proposed mechanisms resides in the uncertainty concerning the number and sources of proton transfers. Although specific protonation events are key features in determining the specificity and efficiency of the two catalytic steps, little is known about the role and properties of protons from the substrate, cofactors, and H-bond network in the vicinity of the heme active site. In this study, we have investigated the role of the acidic proton from the L-Arg guanidinium moiety on the stability and reactivity of the ferrous heme-oxy complex intermediate by exploiting a series of L-Arg analogues exhibiting a wide range of guanidinium pK(a) values. Using electrochemical and vibrational spectroscopic techniques, we have analyzed the effects of the analogues on the heme, including characteristics of its proximal ligand, heme conformation, redox potential, and electrostatic properties of its distal environment. Our results indicate that the substrate guanidinium pK(a) value significantly affects the H-bond network near the heme distal pocket. Our results lead us to propose a new structural model where the properties of the guanidinium moiety finely control the proton transfer events in NOS and tune its oxidative chemistry. This model may account for the discrepancies found in previously proposed mechanisms of NOS oxidation processes.
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Affiliation(s)
- Claire Giroud
- Laboratoire Stress Oxydants et Detoxication, Commissariat à l'Energie Atomique Saclay, Institut de Biologie et de Technologies de Saclay, 91191 Gif-sur-Yvette Cedex, France
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21
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Doukov T, Li H, Soltis M, Poulos TL. Single crystal structural and absorption spectral characterizations of nitric oxide synthase complexed with N(omega)-hydroxy-L-arginine and diatomic ligands. Biochemistry 2009; 48:10246-54. [PMID: 19791770 DOI: 10.1021/bi9009743] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The X-ray structures of neuronal nitric oxide synthase (nNOS) with N(omega)-hydroxy-l-arginine (l-NHA) and CO (or NO) bound have been determined at 1.91-2.2 A resolution. Microspectrophotometric techniques confirmed reduced redox state and the status of diatomic ligand complexes during X-ray diffraction data collection. The structure of nNOS-NHA-NO, a close mimic to the dioxygen complex, provides a picture of the potential interactions between the heme-bound diatomic ligand, substrate l-NHA, and the surrounding protein and solvent structure environment. The OH group of l-NHA in the X-ray structures deviates from the plane of the guanidinium moiety substantially, indicating that the OH-bearing, protonated guanidine N(omega) nitrogen of l-NHA has substantial sp(3) hybridization character. This nitrogen geometry, different from that of the guanidinium N(omega) nitrogen of l-arginine, allows a hydrogen bond to be donated to the proximal oxygen of the heme-bound dioxygen complex, thus preventing cleavage of the O-O bond. Instead, it favors the stabilization of the ferric-hydroperoxy intermediate, Fe(3+)-OOH(-), which serves as the active oxidant in the conversion of l-NHA to NO and citrulline in the second reaction of the NOS.
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Affiliation(s)
- Tzanko Doukov
- Macromolecular Crystallographic Group, The Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford, California 94309, USA
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22
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Martin NI, Woodward JJ, Winter MB, Marletta MA. 4,4-Difluorinated analogues of l-arginine and N(G)-hydroxy-l-arginine as mechanistic probes for nitric oxide synthase. Bioorg Med Chem Lett 2009; 19:1758-62. [PMID: 19230661 DOI: 10.1016/j.bmcl.2009.01.076] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2008] [Revised: 01/21/2009] [Accepted: 01/22/2009] [Indexed: 10/21/2022]
Abstract
4,4-Difluoro-l-arginine and 4,4-difluoro-N(G)-hydroxy-l-arginine were synthesized and shown to be substrates for the inducible isoform of nitric oxide synthase (iNOS). Binding of both fluorinated analogues to the NOS active site was also investigated using a spectral binding assay employing a heme domain construct of the inducible NOS isoform (iNOS(heme)). 4,4-Difluoro-N(G)-hydroxy-arginine was found to bind at the NOS active site in a unique manner consistent with a model involving ligation of the Fe(III) heme center by the oxygen atom of the N(G)-hydroxy moiety.
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Affiliation(s)
- Nathaniel I Martin
- Department of Medicinal Chemistry and Chemical Biology, University of Utrecht, 3584 CA, The Netherlands
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23
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Cho KB, Carvajal MA, Shaik S. First Half-Reaction Mechanism of Nitric Oxide Synthase: The Role of Proton and Oxygen Coupled Electron Transfer in the Reaction by Quantum Mechanics/Molecular Mechanics. J Phys Chem B 2008; 113:336-46. [DOI: 10.1021/jp8073199] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kyung-Bin Cho
- Institute of Chemistry and The Lise Meitner-Minerva Center for Quantum Computational Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Maria Angels Carvajal
- Institute of Chemistry and The Lise Meitner-Minerva Center for Quantum Computational Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Sason Shaik
- Institute of Chemistry and The Lise Meitner-Minerva Center for Quantum Computational Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
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24
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Robinet JJ, Cho KB, Gauld JW. A density functional theory investigation on the mechanism of the second half-reaction of nitric oxide synthase. J Am Chem Soc 2008; 130:3328-34. [PMID: 18293966 DOI: 10.1021/ja072650+] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Density functional theory methods have been employed to systematically investigate the overall mechanism of the second half-reaction of nitric oxide synthases. The initial heme-bound hydrogen peroxide intermediate previously identified is found to first undergo a simple rotation about its O-O peroxide bond. Then, via a "ping-pong" peroxidase-like mechanism the -O(in)H- proton is transferred back onto the substrate's -NO oxygen then subsequently onto the outer oxygen of the resulting Fe(heme)-OOH species. As a result, O(out) is released as H2O with concomitant formation of a compound I-type (Fe(heme)-O) species. Formation of the final citrulline and NO products can then be achieved in one step via a tetrahedral transition structure resulting from direct attack of the Fe(heme)-O moiety at the substrate's guanidinium carbon center. The possible role of alternative mechanisms involving a protonated compound II-type species or an initial transfer of only the -NH- hydrogen of the =NHOH+ group of N(omega)-hydroxy-L-arginine is also discussed.
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Affiliation(s)
- Jesse J Robinet
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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25
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Chartier FJM, Couture M. Substrate-specific Interactions with the Heme-bound Oxygen Molecule of Nitric-oxide Synthase. J Biol Chem 2007; 282:20877-86. [PMID: 17537725 DOI: 10.1074/jbc.m701800200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report the characterization by resonance Raman spectroscopy of the oxygenated complex (Fe(II)O(2)) of nitric-oxide synthases of Staphylococcus aureus (saNOS) and Bacillus subtilis (bsNOS) saturated with N(omega)-hydroxy-l-arginine. The frequencies of the nu(Fe-O) and nu(O-O) modes were 530 and 1135 cm(-), respectively, in both the presence and absence of tetrahydrobiopterin. On the basis of a comparison of these frequencies with those of saNOS and bsNOS saturated with l-arginine (nu(Fe-O) at 517 cm(-1) and nu(O-O) at 1123 cm(-1)) and those of substrate-free saNOS (nu(Fe-O) at 517 and nu(O-O) at 1135 cm(-1)) (Chartier, F. J. M., Blais, S. P., and Couture, M. (2006) J. Biol. Chem. 281, 9953-9962), we propose two models that account for the frequency shift of nu(Fe-O) (but not nu(O-O)) upon N(omega)-hydroxy-l-arginine binding as well as the frequency shift of nu(O-O) (but not nu(Fe-O)) upon l-arginine binding. The implications of these substrate-specific interactions with respect to catalysis by NOSs are discussed.
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Affiliation(s)
- François J M Chartier
- Département de Biochimie et de Microbiologie and the Centre de Recherche sur la Fonction, la Structure, et l'Ingénierie des Protéines, Université Laval, Quebec City, Quebec G1K 7P4, Canada
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26
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Li H, Igarashi J, Jamal J, Yang W, Poulos TL. Structural studies of constitutive nitric oxide synthases with diatomic ligands bound. J Biol Inorg Chem 2006; 11:753-68. [PMID: 16804678 DOI: 10.1007/s00775-006-0123-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Accepted: 05/18/2006] [Indexed: 10/24/2022]
Abstract
Crystal structures are reported for the endothelial nitric oxide synthase (eNOS)-arginine-CO ternary complex as well as the neuronal nitric oxide synthase (nNOS) heme domain complexed with L: -arginine and diatomic ligands, CO or NO, in the presence of the native cofactor, tetrahydrobiopterin, or its oxidized analogs, dihydrobiopterin and 4-aminobiopterin. The nature of the biopterin has no influence on the diatomic ligand binding. The binding geometries of diatomic ligands to nitric oxide synthase (NOS) follow the {MXY}(n) formalism developed from the inorganic diatomic-metal complexes. The structures reveal some subtle structural differences between eNOS and nNOS when CO is bound to the heme which correlate well with the differences in CO stretching frequencies observed by resonance Raman techniques. The detailed hydrogen-bonding geometries depicted in the active site of nNOS structures indicate that it is the ordered active-site water molecule rather than the substrate itself that would most likely serve as a direct proton donor to the diatomic ligands (CO, NO, as well as O(2)) bound to the heme. This has important implications for the oxygen activation mechanism critical to NOS catalysis.
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Affiliation(s)
- Huiying Li
- Department of Molecular Biology and Biochemistry, Center in Chemical and Structural Biology, University of California, Irvine, CA 92697-3900, USA
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27
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Porasuphatana S, Weaver J, Rosen GM. Inducible nitric oxide synthase catalyzes ethanol oxidation to α-hydroxyethyl radical and acetaldehyde. Toxicology 2006; 223:167-74. [PMID: 16713055 DOI: 10.1016/j.tox.2006.02.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 02/26/2006] [Accepted: 02/28/2006] [Indexed: 11/17/2022]
Abstract
The physiologic function of nitric oxide synthases, independent of the isozyme, is well established, metabolizing L-arginine to L-citrulline and nitric oxide (NO). This enzyme can also transfer electrons to O2, affording superoxide (O2*-) and hydrogen peroxide (H2O2). We have demonstrated that NOS1, in the presence of L-arginine, can biotransform ethanol (EtOH) to alpha-hydroxyethyl radical (CH3*CHOH). We now report that a competent NOS2 with l-arginine can, like NOS1, oxidize EtOH to CH3*CHOH. Once this free radical is formed, it is metabolized to acetaldehyde as shown by LC-ESI-MS/MS and HPLC analysis. These observations suggest that NOS2 can behave similarly to cytochrome P-450 in the catalysis of acetaldehyde formation from ethanol via the generation of alpha-hydroxyethyl radical when L-arginine is present.
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Affiliation(s)
- Supatra Porasuphatana
- Department of Toxicology, Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand.
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28
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Sudhamsu J, Crane BR. Structure and reactivity of a thermostable prokaryotic nitric-oxide synthase that forms a long-lived oxy-heme complex. J Biol Chem 2006; 281:9623-32. [PMID: 16407211 DOI: 10.1074/jbc.m510062200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In an effort to generate more stable reaction intermediates involved in substrate oxidation by nitric-oxide synthases (NOSs), we have cloned, expressed, and characterized a thermostable NOS homolog from the thermophilic bacterium Geobacillus stearothermophilus (gsNOS). As expected, gsNOS forms nitric oxide (NO) from l-arginine via the stable intermediate N-hydroxy l-arginine (NOHA). The addition of oxygen to ferrous gsNOS results in long-lived heme-oxy complexes in the presence (Soret peak 427 nm) and absence (Soret peak 413 nm) of substrates l-arginine and NOHA. The substrate-induced red shift correlates with hydrogen bonding between substrate and heme-bound oxygen resulting in conversion to a ferric heme-superoxy species. In single turnover experiments with NOHA, NO forms only in the presence of H(4)B. The crystal structure of gsNOS at 3.2 AA of resolution reveals great similarity to other known bacterial NOS structures, with the exception of differences in the distal heme pocket, close to the oxygen binding site. In particular, a Lys-356 (Bacillus subtilis NOS) to Arg-365 (gsNOS) substitution alters the conformation of a conserved Asp carboxylate, resulting in movement of an Ile residue toward the heme. Thus, a more constrained heme pocket may slow ligand dissociation and increase the lifetime of heme-bound oxygen to seconds at 4 degrees C. Similarly, the ferric-heme NO complex is also stabilized in gsNOS. The slow kinetics of gsNOS offer promise for studying downstream intermediates involved in substrate oxidation.
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Affiliation(s)
- Jawahar Sudhamsu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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29
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Pennington RL, Sha X, King SB. N-Hydroxy sulfonimidamides as new nitroxyl (HNO) donors. Bioorg Med Chem Lett 2005; 15:2331-4. [PMID: 15837319 DOI: 10.1016/j.bmcl.2005.02.082] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 02/24/2005] [Accepted: 02/28/2005] [Indexed: 11/16/2022]
Abstract
Chlorination and condensation of simple sulfinamides with O-benzyl and O-tert-butyl dimethyl siloxy hydroxylamine gives O-protected N-hydroxy sulfonimidamides. Deprotection of these compounds produces the corresponding sulfinamide and nitrous oxide, which provides evidence for the intermediacy of nitroxyl (HNO) and identifies these compounds as new potential HNO donors.
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Affiliation(s)
- Richard L Pennington
- Department of Chemistry, College of St. Mary, 1901 S. 72nd Street, Omaha, NE 68124-2377, USA
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30
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Ost TWB, Daff S. Thermodynamic and kinetic analysis of the nitrosyl, carbonyl, and dioxy heme complexes of neuronal nitric-oxide synthase. The roles of substrate and tetrahydrobiopterin in oxygen activation. J Biol Chem 2004; 280:965-73. [PMID: 15507439 DOI: 10.1074/jbc.m411191200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian NO synthases catalyze the monooxygenation of L-arginine (L-Arg) to N-hydroxyarginine (NOHA) and the subsequent monooxygenation of this to NO and citrulline. Both steps proceed via formation of an oxyferrous heme complex and may ultimately lead to a ferrous NO complex, from which NO must be released. Electrochemical reduction of NO-bound neuronal nitricoxide synthase (nNOS) oxygenase domain was used to form the ferrous heme NO complex, which was found to be stable only in the presence of low NO concentrations, due to catalytic degradation of NO at the nNOS heme site. The reduction potential for the heme-NO complex was approximately -140 mV, which shifted to 0 mV in the presence of either L-Arg or NOHA. This indicates that the complex is stabilized by 14 kJ mol(-1) in the presence of substrate, consistent with a strong H-bonding interaction between NO and the guanidino group. Neither substrate influenced the reduction potential of the ferrous heme CO complex, however. Both L-Arg and NOHA appear to interact with bound NO in a similar way, indicating that both bind as guanidinium ions. The dissociation constant for NO bound to ferrous heme in the presence of l-Arg was determined electrochemically to be 0.17 nM, and the rate of dissociation was estimated to be 10(-4) s(-1), which is much slower than the rate of catalysis. Stopped-flow kinetic analysis of oxyferrous formation and decay showed that both l-Arg and NOHA also stabilize the ferrous heme dioxy complex, resulting in a 100-fold decrease in its rate of decay. Electron transfer from the active-site cofactor tetrahydrobiopterin (H4B) has been proposed to trigger the monoxygenation process. Consistent with this, substitution by the analogue/inhibitor 4-amino-H4B stabilized the oxyferrous complex by a further two orders of magnitude. H4B is required, therefore, to break down both the oxyferrousand ferrous nitrosyl complexes of nNOS during catalysis. The energetics of these processes necessitates an electron donor/acceptor operating within a specific reduction potential range, defining the role of H4B.
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Affiliation(s)
- Tobias W B Ost
- School of Chemistry, University of Edinburgh, King's Bldgs., West Mains Rd., Edinburgh EH9 3JJ, United Kingdom
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Matter H, Kotsonis P. Biology and chemistry of the inhibition of nitric oxide synthases by pteridine-derivatives as therapeutic agents. Med Res Rev 2004; 24:662-84. [PMID: 15224385 DOI: 10.1002/med.20005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Inhibitors of the family of nitric oxide synthases (NOS-I-III; EC 1.14.13.39) are of interest as pharmacological agents to modulate pathologically high nitric oxide (NO) levels in inflammation, sepsis, and stroke. In this article, we discuss the approach for targeting the unique (6R)-5,6,7,8-tetrahydro-L-biopterin (H4Bip) binding site of NOS by appropriate inhibitors. This binding site maximally increases enzyme activity and NO production from the substrate L-arginine upon cofactor binding. The first generation of H4Bip-based NOS inhibitors was based on 4-amino H4Bip derivatives in analogy to anti-folates such as methotrexate. In addition, we discuss the structure-activity relationship of a related series of 4-oxo-pteridine derivatives. Furthermore, molecular modeling studies provide an understanding of pterin antagonism on a structural level based on favorable and unfavorable interactions between protein binding site and ligands. These techniques include 3D-QSAR (CoMFA, CoMSIA) to understand ligand affinity and GRID/consensus principal component analysis (CPCA) to learn about selectivity requirements. Collectively these approaches, in combination with the presented SAR and structural data, provide useful information for the design of novel NOS inhibitors with increased isoform selectivity.
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Affiliation(s)
- Hans Matter
- Aventis Pharma Deutschland GmbH, DI&A Chemistry, Molecular Modelling, Building G 878, D-65926, Frankfurt am Main, Germany.
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32
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Maldotti A, Molinari A, Vitali I, Ganzaroli E, Battioni P, Mathieu D, Mansuy D. Oxidation ofN-(4-Chlorophenyl)-N′-hydroxyguanidine toN-(4-Chlorophenyl)urea and Nitric Oxide by Photoexcited Iron Porphyrins. Eur J Inorg Chem 2004. [DOI: 10.1002/ejic.200400056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Stuehr DJ, Santolini J, Wang ZQ, Wei CC, Adak S. Update on mechanism and catalytic regulation in the NO synthases. J Biol Chem 2004; 279:36167-70. [PMID: 15133020 DOI: 10.1074/jbc.r400017200] [Citation(s) in RCA: 368] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Dennis J Stuehr
- Department of Immunology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
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Werner ER, Gorren ACF, Heller R, Werner-Felmayer G, Mayer B. Tetrahydrobiopterin and nitric oxide: mechanistic and pharmacological aspects. Exp Biol Med (Maywood) 2003; 228:1291-302. [PMID: 14681545 DOI: 10.1177/153537020322801108] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In previous minireviews in this journal, we discussed work on induction of tetrahydrobiopterin biosynthesis by cytokines and its significance for nitric oxide (NO) production of intact cells as well as functions of H4-biopterin identified at this time for NO synthases (Proc Soc Exp Biol Med 203: 1-12, 1993; Proc Soc Exp Biol Med 219: 171-182, 1998). Meanwhile, the recognition of the importance of tetrahydrobiopterin for NO formation has led to new insights into complex biological processes and revealed possible novel pharmacological strategies to intervene in certain pathological conditions. Recent work could also establish that tetrahydrobiopterin, in addition to its allosteric effects, is redox-active in the NO synthase reaction. In this review, we summarize the current view of how tetrahydrobiopterin functions in the generation of NO and focus on pharmacological aspects of tetrahydrobiopterin availability with emphasis on endothelial function.
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Affiliation(s)
- Ernst R Werner
- Institute for Medical Chemistry and Biochemistry, University of Innsbruck, A-6020 Innsbruck, Austria.
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Wei CC, Wang ZQ, Hemann C, Hille R, Stuehr DJ. A tetrahydrobiopterin radical forms and then becomes reduced during Nomega-hydroxyarginine oxidation by nitric-oxide synthase. J Biol Chem 2003; 278:46668-73. [PMID: 14504282 DOI: 10.1074/jbc.m307682200] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitric-oxide synthases are flavoheme enzymes that catalyze two sequential monooxygenase reactions to generate nitric oxide (NO) from l-arginine. We investigated a possible redox role for the enzyme-bound cofactor 6R-tetrahydrobiopterin (H4B) in the second reaction of NO synthesis, which is conversion of N-hydroxy-l-arginine (NOHA) to NO plus citrulline. We used stopped-flow spectroscopy and rapid-freeze EPR spectroscopy to follow heme and biopterin transformations during single-turnover NOHA oxidation reactions catalyzed by the oxygenase domain of inducible nitric-oxide synthase (iNOSoxy). Significant biopterin radical (>0.5 per heme) formed during reactions catalyzed by iNOSoxy that contained either H4B or 5-methyl-H4B. Biopterin radical formation was kinetically linked to conversion of a heme-dioxy intermediate to a heme-NO product complex. The biopterin radical then decayed within a 200-300-ms time period just prior to dissociation of NO from a ferric heme-NO product complex. Measures of final biopterin redox status showed that biopterin radical decay occurred via an enzymatic one-electron reduction process that regenerated H4B (or 5MeH4B). These results provide evidence of a dual redox function for biopterin during the NOHA oxidation reaction. The data suggest that H4B first provides an electron to a heme-dioxy intermediate, and then the H4B radical receives an electron from a downstream reaction intermediate to regenerate H4B. The first one-electron transition enables formation of the heme-based oxidant that reacts with NOHA, while the second one-electron transition is linked to formation of a ferric heme-NO product complex that can release NO from the enzyme. These redox roles are novel and expand our understanding of biopterin function in biology.
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Affiliation(s)
- Chin-Chuan Wei
- Department of Immunology, The Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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What form of NG-hydroxy-L-arginine is the intermediate in the mechanism of NO synthase? QM and QM/MM calculations of substrate–active site interactions. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0166-1280(03)00305-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Groves JT. The bioinorganic chemistry of iron in oxygenases and supramolecular assemblies. Proc Natl Acad Sci U S A 2003; 100:3569-74. [PMID: 12655056 PMCID: PMC152962 DOI: 10.1073/pnas.0830019100] [Citation(s) in RCA: 282] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The bioinorganic chemistry of iron is central to life processes. Organisms must recruit iron from their environment, control iron storage and trafficking within cells, assemble the complex, iron-containing redox cofactors of metalloproteins, and manage a myriad of biochemical transformations by those enzymes. The coordination chemistry and the variable oxidation states of iron provide the essential mechanistic machinery of this metabolism. Our current understanding of several aspects of the chemistry of iron in biology are discussed with an emphasis on the oxygen activation and transfer reactions mediated by heme and nonheme iron proteins and the interactions of amphiphilic iron siderophores with lipid membranes.
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Affiliation(s)
- John T Groves
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
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Abstract
Nitric oxide synthase (NOS) is an example of a family of heme-containing monooxygenases that, under the restricted control of a specific substrate, can generate free radicals. While the generation of nitric oxide (NO*) depends solely on the binding of L-arginine, NOS produces superoxide (O(2)*(-)) and hydrogen peroxide (H(2)O(2)) when the concentration of the substrate is low. Not surprisingly, effort has been put forth to understand the pathway by which NOS generates NO*, O(2)*(-) and H(2)O(2), including the role of substrate binding in determining the pathways by which free radicals are generated. By binding within the distal heme pocket near the sixth coordination position of the NOS heme iron, L-arginine alters the coordination properties of the heme iron that promotes formation of the perferryl complex NOS-[Fe(5+)=O](3+). This reactive iron intermediate has been shown to abstract a hydrogen atom from a carbon alpha to a heteroatom and generate carbon-centered free radicals. The ability of NOS to produce free radicals during enzymic cycling demonstrates that NOS-[Fe(5+)=O](3+) behaves like an analogous iron-oxo complex of cytochrome P-450 during aliphatic hydroxylation. The present review discusses the mechanism(s) by which NOS generates secondary free radicals that may initiate pathological events, along with the cell signaling properties of NO*, O(2)*(-) and H(2)O(2).
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Affiliation(s)
- Supatra Porasuphatana
- Department of Toxicology, Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand.
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Fedorov R, Ghosh DK, Schlichting I. Crystal structures of cyanide complexes of P450cam and the oxygenase domain of inducible nitric oxide synthase-structural models of the short-lived oxygen complexes. Arch Biochem Biophys 2003; 409:25-31. [PMID: 12464241 DOI: 10.1016/s0003-9861(02)00555-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The crystal structure of the ternary cyanide complex of P450cam and camphor was determined to 1.8A resolution and found to be identical with the structure of the active oxygen complex [I. Schlichting et al., 2000, Science 287, 1615]. Notably, cyanide binds in a bent mode and induces the active conformation that is characterized by the presence of two water molecules and a flip of the carbonyl of the conserved Asp251. The structure of the ternary complex of cyanide, L-arginine, and the oxygenase domain of inducible nitric oxide synthase was determined to 2.4A resolution. Cyanide binds essentially linearly, interacts with L-Arg, and induces the binding of a water molecule at the active site. This water is positioned by backbone interactions, located 2.8A from the nitrogen atom of cyanide, and could provide a proton required for O-O bond scission in the hydroxylation reaction of nitric oxide synthase.
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Affiliation(s)
- Roman Fedorov
- Abt. Biophysikalische Chemie, Max Planck Institut für Molekulare Physiologie, Otto Hahn Strasse 11, 44227 Dortmund, Germany
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Darbeau RW, Pease RS, Perez EV. Electronic effects in the N-nitrosation of N-benzylpivalamides. J Org Chem 2002; 67:2942-7. [PMID: 11975550 DOI: 10.1021/jo011002k] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of N-4-R-benzylpivalamides (R = MeO, Me, H, CF(3), and NO(2)) was nitrosated using a standardized solution of N(2)O(4) in CDCl(3) at -40 degrees C. The reactions, which produced the corresponding N-4-R-benzyl-N-nitrosopivalamides, were followed by (1)H NMR spectroscopy. The rate of nitrosation was found to vary in a systematic way with the nature of the 4-R-group on the aromatic ring. Thus, electron-releasing groups increased the rate of the reaction, whereas electron-withdrawing ones decelerated N-nitrosation. In a similar fashion, the nitrosations were accelerated in polar solvents but were slower in solvents of low polarity. The sensitivities of N-nitrosation to these intra- and intermolecular electronic effects are compared to those from a previous study examining the dependence of the kinetics of nitrosoamide thermolyses on the same factors.
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Affiliation(s)
- Ron W Darbeau
- Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609, USA.
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41
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Wang ZQ, Wei CC, Stuehr DJ. A conserved tryptophan 457 modulates the kinetics and extent of N-hydroxy-L-arginine oxidation by inducible nitric-oxide synthase. J Biol Chem 2002; 277:12830-7. [PMID: 11823464 DOI: 10.1074/jbc.m111967200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the oxygenase domain of mouse inducible nitric-oxide synthase (iNOSoxy), a conserved tryptophan residue, Trp-457, regulates the kinetics and extent of l-Arg oxidation to N(omega)-hydroxy-l-arginine (NOHA) by controlling electron transfer between bound (6R)-tetrahydrobiopterin (H(4)B) cofactor and the enzyme heme Fe(II)O(2) intermediate (Wang, Z. Q., Wei, C. C., Ghosh, S., Meade, A. L., Hemann, C., Hille, R., and Stuehr, D. J. (2001) Biochemistry 40, 12819-12825). To investigate whether NOHA oxidation to citrulline and nitric oxide (NO) is regulated by a similar mechanism, we performed single turnover reactions with wild type iNOSoxy and mutants W457F and W457A. Ferrous proteins containing NOHA plus H(4)B or NOHA plus 7,8-dihydrobiopterin (H(2)B), were mixed with O(2)-containing buffer, and then heme spectral transitions and product formation were followed versus time. All three proteins formed a Fe(II)O(2) intermediate with identical spectral characteristics. In wild type, H(4)B increased the disappearance rate of the Fe(II)O(2) intermediate relative to H(2)B, and its disappearance was coupled to the formation of a Fe(III)NO immediate product prior to formation of ferric enzyme. In W457F and W457A, the disappearance rate of the Fe(II)O(2) intermediate was slower than in wild type and took place without detectable build-up of the heme Fe(III)NO immediate product. Rates of Fe(II)O(2) disappearance correlated with rates of citrulline formation in all three proteins, and reactions containing H(4)B formed 1.0, 0.54, and 0.38 citrulline/heme in wild type, W457F, and W457A iNOSoxy, respectively. Thus, Trp-457 modulates the kinetics of NOHA oxidation by iNOSoxy, and this is important for determining the extent of citrulline and NO formation. Our findings support a redox role for H(4)B during NOHA oxidation to NO by iNOSoxy.
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Affiliation(s)
- Zhi-Qiang Wang
- Department of Immunology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA
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Affiliation(s)
- Gerald M Rosen
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
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Porasuphatana S, Tsai P, Pou S, Rosen GM. Perferryl complex of nitric oxide synthase: role in secondary free radical formation. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1569:111-6. [PMID: 11853964 DOI: 10.1016/s0304-4165(01)00241-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Neuronal nitric oxide synthase (NOS I) has been shown to generate nitric oxide (NO*) and superoxide (O(2)*-)during enzymatic cycling, the ratio of each free radical is dependent upon the concentration of L-arginine. Using spin trapping and electron paramagnetic resonance (EPR) spectroscopy, we recently reported that NOS I can oxidize ethanol (EtOH) to alpha-hydroxyethyl radical (CH(3)*CHOH). We speculated that the perferryl complex of NOS, (NOS-[Fe(5+)[double bond]O](3+)) was responsible for the generation of CH(3)*CHOH. Using potassium monopersulfate (KHSO(5)) to oxidize the heme of NOS I to NOS-[Fe(5+)[double bond]O](3+), we were able to demonstrate that this perferryl complex can oxidize L-arginine to L-citrulline and NO*. Even in the absence of L-arginine, EtOH was oxidized to CH(3)*CHOH by NOS-[Fe(5+)[double bond]O](3+). Sodium cyanide (NaCN), a heme blocker, inhibited the formation of CH(3)*CHOH by NOS.
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Affiliation(s)
- Supatra Porasuphatana
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, 21201, USA
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