1
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Huang P, Luo H, Chen C, Li P, Xu B. Bacterial nitric oxide synthase in colorizing meat products: Current development and future directions. Crit Rev Food Sci Nutr 2022; 64:4362-4372. [PMID: 36322689 DOI: 10.1080/10408398.2022.2141679] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Nitrite has been widely used in meat products for its abilities including color formation, antimicrobial properties, flavor formation and preventing lipid oxidation. However, the possible generation of N-nitrosamines through reaction of nitrite with secondary amines arises many concerns in the usage of nitrite. For a long time, nitrite substitution is unsettled issue in the meat industry. Many attempts have been tried, however, the alternative solutions are often ephemeral and palliative. In recent years, bacterial nitric oxide synthase (bNOS) has received attention for its critical roles, especially in reddening meat products. This comprehensive background study summarizes the application of bNOS in colorizing meat products, its functions in bacteria, and methods of regulating the bNOS pathway. Based on this information, some strategies for promoting the nitric oxide yield for effectively substituting nitrite are presented, such as changing the environmental conditions for bacterial survival and adding substrate. Thus, bNOS is a promising nitrite substitute for color formation, and further research on its other roles in meat needs to be carried out to obtain the complete picture.
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Affiliation(s)
- Pan Huang
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, China
| | - Huiting Luo
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, China
| | - Conggui Chen
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, China
| | - Peijun Li
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, China
| | - Baocai Xu
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, China
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2
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Gee LC, Massimo G, Lau C, Primus C, Fernandes D, Chen J, Rathod KS, Hamers AJP, Filomena F, Nuredini G, Ibrahim AS, Khambata RS, Gupta AK, Moon JC, Kapil V, Ahluwalia A. Inorganic nitrate attenuates cardiac dysfunction: role for xanthine oxidoreductase and nitric oxide. Br J Pharmacol 2021; 179:4757-4777. [PMID: 34309015 DOI: 10.1111/bph.15636] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 07/01/2021] [Accepted: 07/03/2021] [Indexed: 11/28/2022] Open
Abstract
Nitric oxide (NO) is a vasodilator and independent modulator of cardiac remodelling. Commonly, in cardiac disease (e.g. heart failure) endothelial dysfunction (synonymous with NO-deficiency) has been implicated in increased blood pressure (BP), cardiac hypertrophy and fibrosis. Currently no effective therapies replacing NO have succeeded in the clinic. Inorganic nitrate (NO3 - ), through chemical reduction to nitrite and then NO, exerts potent BP-lowering but whether it might be useful in treating undesirable cardiac remodelling is unknown. In a nested age- and sex-matched case-control study of hypertensive patients +/- left ventricular hypertrophy (NCT03088514) we show that lower plasma nitrite concentration and vascular dysfunction accompany cardiac hypertrophy and fibrosis in patients. In mouse models of cardiac remodelling, we also show that restoration of circulating nitrite levels using dietary nitrate improves endothelial dysfunction through targeting of xanthine oxidoreductase (XOR)-driven H2 O2 and superoxide, and reduces cardiac fibrosis through NO-mediated block of SMAD-phosphorylation leading to improvements in cardiac structure and function. We show that via these mechanisms dietary nitrate offers easily translatable therapeutic options for treatment of cardiac dysfunction.
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Affiliation(s)
- Lorna C Gee
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Gianmichele Massimo
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Clement Lau
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Christopher Primus
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Daniel Fernandes
- Departamento de Farmacologia, Federal University of Santa Catarina, Florianópolis, Santa Catarina,, Brazil
| | - Jianmin Chen
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Krishnaraj S Rathod
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Alexander Jozua Pedro Hamers
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Federica Filomena
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Gani Nuredini
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Abdiwahab Shidane Ibrahim
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Rayomand S Khambata
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Ajay K Gupta
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - James C Moon
- UCL Institute of Cardiovascular Science, University College London, London, UK
| | - Vikas Kapil
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
| | - Amrita Ahluwalia
- William Harvey Research Institute, Barts & The London School of Medicine & Dentistry, Queen Mary University of London, London, UK
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3
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Gebhart V, Reiß K, Kollau A, Mayer B, Gorren ACF. Site and mechanism of uncoupling of nitric-oxide synthase: Uncoupling by monomerization and other misconceptions. Nitric Oxide 2019; 89:14-21. [PMID: 31022534 DOI: 10.1016/j.niox.2019.04.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 03/15/2019] [Accepted: 04/15/2019] [Indexed: 01/20/2023]
Abstract
Nitric oxide synthase (NOS) catalyzes the transformation of l-arginine, molecular oxygen (O2), and NADPH-derived electrons to nitric oxide (NO) and l-citrulline. Under some conditions, however, NOS catalyzes the reduction of O2 to superoxide (O2-) instead, a phenomenon that is generally referred to as uncoupling. In principle, both the heme in the oxygenase domain and the flavins in the reductase domain could catalyze O2- formation. In the former case the oxyferrous (Fe(II)O2) complex that is formed as an intermediate during catalysis would dissociate to heme and O2-; in the latter case the reduced flavins would reduce O2 to O2-. The NOS cofactor tetrahydrobiopterin (BH4) is indispensable for coupled catalysis. In the case of uncoupling at the heme this is explained by the essential role of BH4 as an electron donor to the oxyferrous complex; in the case of uncoupling at the flavins it is assumed that the absence of BH4 results in NOS monomerization, with the monomers incapable to sustain NO synthesis but still able to support uncoupled catalysis. In spite of little supporting evidence, uncoupling at the reductase after NOS monomerization appears to be the predominant hypothesis at present. To set the record straight we extended prior studies by determining under which conditions uncoupling of the neuronal and endothelial isoforms (nNOS and eNOS) occurred and if a correlation exists between uncoupling and the monomer/dimer equilibrium. We determined the rates of coupled/uncoupled catalysis by measuring NADPH oxidation spectrophotometrically at 340 nm and citrulline synthesis as the formation of [3H]-citrulline from [3H]-Arg. The monomer/dimer equilibrium was determined by FPLC and, for comparison, by low-temperature polyacrylamide gel electrophoresis. Uncoupling occurred in the absence of Arg and/or BH4, but not in the absence of Ca2+ or calmodulin (CaM). Since omission of Ca2+/CaM will completely block heme reduction while still allowing substantial FMN reduction, this argues against uncoupling by the reductase domain. In the presence of heme-directed NOS inhibitors uncoupling occurred to the extent that these compound allowed heme reduction, again arguing in favor of uncoupling at the heme. The monomer/dimer equilibrium showed no correlation with uncoupling. We conclude that uncoupling by BH4 deficiency takes place exclusively at the heme, with virtually no contribution from the flavins and no role for NOS monomerization.
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Affiliation(s)
- Verena Gebhart
- Department of Pharmacology and Toxicology Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Katja Reiß
- Department of Pharmacology and Toxicology Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Alexander Kollau
- Department of Pharmacology and Toxicology Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Bernd Mayer
- Department of Pharmacology and Toxicology Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Antonius C F Gorren
- Department of Pharmacology and Toxicology Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria.
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4
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Stuehr DJ, Haque MM. Nitric oxide synthase enzymology in the 20 years after the Nobel Prize. Br J Pharmacol 2019; 176:177-188. [PMID: 30402946 PMCID: PMC6295403 DOI: 10.1111/bph.14533] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/25/2018] [Accepted: 10/31/2018] [Indexed: 12/31/2022] Open
Abstract
This review briefly summarizes what was known about NOS enzymology at the time of the Nobel Prize award in 1998 and then discusses from the author's perspective some of the advances in NOS enzymology over the subsequent 20 years, focused on five aspects: the maturation process of NOS enzymes and its regulation; the mechanism of NO synthesis; the redox roles played by the 6R-tetrahydrobiopterin cofactor; the role of protein conformational behaviour in enabling NOS electron transfer and its regulation by NOS structural elements and calmodulin, and the catalytic cycling pathways of NOS enzymes and their influence on NOS activity. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.
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Affiliation(s)
- Dennis J Stuehr
- Department of Inflammation and Immunity, Lerner Research InstituteThe Cleveland ClinicClevelandOHUSA
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5
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Hutfless EH, Chaudhari SS, Thomas VC. Emerging Roles of Nitric Oxide Synthase in Bacterial Physiology. Adv Microb Physiol 2018; 72:147-191. [PMID: 29778214 DOI: 10.1016/bs.ampbs.2018.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nitric oxide (NO) is a potent inhibitor of diverse cellular processes in bacteria. Therefore, it was surprising to discover that several bacterial species, primarily Gram-positive organisms, harboured a gene encoding nitric oxide synthase (NOS). Recent attempts to characterize bacterial NOS (bNOS) have resulted in the discovery of structural features that may allow it to function as a NO dioxygenase and produce nitrate in addition to NO. Consistent with this characterization, investigations into the biological function of bNOS have also emphasized a role for NOS-dependent nitrate and nitrite production in aerobic and microaerobic respiration. In this review, we aim to compare, contrast, and summarize the structure, biochemistry, and biological role of bNOS with mammalian NOS and discuss how recent advances in our understanding of bNOS have enabled efforts at designing inhibitors against it.
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Affiliation(s)
| | | | - Vinai C Thomas
- University of Nebraska Medical Center, Omaha, NE, United States.
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6
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Weisslocker-Schaetzel M, Lembrouk M, Santolini J, Dorlet P. Revisiting the Val/Ile Mutation in Mammalian and Bacterial Nitric Oxide Synthases: A Spectroscopic and Kinetic Study. Biochemistry 2017; 56:748-756. [PMID: 28074650 DOI: 10.1021/acs.biochem.6b01018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Nitric oxide is produced in mammals by the nitric oxide synthase (NOS) isoforms at a catalytic site comprising a heme associated with a biopterin cofactor. Through genome sequencing, proteins that are highly homologous to the oxygenase domain of NOSs have been identified, in particular in bacteria. The active site is highly conserved except for a valine residue in the distal pocket that is replaced with an isoleucine in bacteria. This switch was previously reported to influence the kinetics of the reaction. We have used the V346I mutant of the mouse inducible NOS (iNOS) as well as the I224V mutant of the NOS from Bacillus subtilis (bsNOS) to study their spectroscopic signatures in solution and look for potential structural differences compared to their respective wild types. Both mutants seem destabilized in the absence of substrate and cofactor. When both substrate and cofactor are present, small differences can be detected with Nω-hydroxy-l-arginine compared to arginine, which is likely due to the differences in the hydrogen bonding network of the distal pocket. Stopped-flow experiments evidence significant changes in the kinetics of the reaction due to the mutation as was already known. We found these effects particularly marked for iNOS. On the basis of these results, we performed rapid freeze-quench experiments to trap the biopterin radical and found the same results that we had obtained for the wild types. Despite differences in kinetics, a radical could be trapped in both steps for the iNOS mutant but only for the first step in the mutant of bsNOS. This strengthens the hypothesis that mammalian and bacterial NOSs may have a different mechanism during the second catalytic step.
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Affiliation(s)
- Marine Weisslocker-Schaetzel
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay , F-91198 Gif-sur-Yvette cedex, France
| | - Mehdi Lembrouk
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay , F-91198 Gif-sur-Yvette cedex, France
| | - Jérôme Santolini
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay , F-91198 Gif-sur-Yvette cedex, France
| | - Pierre Dorlet
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay , F-91198 Gif-sur-Yvette cedex, France
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7
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Brunel A, Lang J, Couture M, Boucher JL, Dorlet P, Santolini J. Oxygen activation in NO synthases: evidence for a direct role of the substrate. FEBS Open Bio 2016; 6:386-97. [PMID: 27419044 PMCID: PMC4856417 DOI: 10.1002/2211-5463.12036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/15/2015] [Accepted: 01/13/2016] [Indexed: 12/13/2022] Open
Abstract
Nitric oxide (NO) and the other reactive nitrogen species (RNOS) play crucial patho‐physiological roles at the interface of oxidative stress and signalling processes. In mammals, the NO synthases (NOSs) are the source of these reactive nitrogen species, and so to understand the precise biological role of RNOS and NO requires elucidation of the molecular functioning of NOS. Oxygen activation, which is at the core of NOS catalysis, involves a sophisticated sequence of electron and proton transfers. While electron transfer in NOS has received much attention, the proton transfer processes has been scarcely investigated. Here, we report an original approach that combines fast‐kinetic techniques coupled to resonance Raman spectroscopy with the use of synthetic analogues of NOS substrate. We characterise FeII‐O2 reaction intermediates in the presence of L‐arginine (Arg), alkyl‐ and aryl‐guanidines. The presence of new reaction intermediates, such as ferric haem‐peroxide, that was formerly postulated, was tracked by analysing the oxygen activation reaction at different times and with different excitation wavelengths. Our results suggest that Arg is not a proton donor, but indirectly intervenes in oxygen activation mechanism by modulating the distal H‐bond network and, in particular, by tuning the position and the role of the distal water molecule. This report supports a catalytic model with two proton transfers in step 1 (Arg hydroxylation) but only one proton transfer in step 2 (Nω‐hydroxy‐L‐arginine oxidation).
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Affiliation(s)
- Albane Brunel
- Laboratoire Stress Oxydant et Détoxication Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Université Paris-Saclay Gif-sur-Yvette Cedex France
| | - Jérôme Lang
- Département de biochimie, de microbiologie et de bio-informatique, and PROTEO Pavillon Charles-Eugène Marchand Université Laval Québec Canada
| | - Manon Couture
- Département de biochimie, de microbiologie et de bio-informatique, and PROTEO Pavillon Charles-Eugène Marchand Université Laval Québec Canada
| | | | - Pierre Dorlet
- Laboratoire Stress Oxydant et Détoxication Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Université Paris-Saclay Gif-sur-Yvette Cedex France
| | - Jérôme Santolini
- Laboratoire Stress Oxydant et Détoxication Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Université Paris-Saclay Gif-sur-Yvette Cedex France
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8
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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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9
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Cheng H, Harris RC. Renal endothelial dysfunction in diabetic nephropathy. Cardiovasc Hematol Disord Drug Targets 2015; 14:22-33. [PMID: 24720460 DOI: 10.2174/1871529x14666140401110841] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 03/21/2014] [Accepted: 03/26/2014] [Indexed: 12/24/2022]
Abstract
Endothelial dysfunction has been posited to play an important role in the pathogenesis of diabetic nephropathy (DN). Due to the heterogeneity of endothelial cells (ECs), it is difficult to generalize about endothelial responses to diabetic stimuli. At present, there are limited techniques fordirectly measuring EC function in vivo, so diagnosis of endothelial disorders still largely depends on indirect assessment of mediators arising from EC injury. In the kidney microcirculation, both afferent and efferent arteries, arterioles and glomerular endothelial cells (GEnC) have all been implicated as targets of diabetic injury. Both hyperglycemia per se, as well as the metabolic consequences of glucose dysregulation, are thought to lead to endothelial cell dysfunction. In this regard, endothelial nitric oxide synthase (eNOS) plays a central role in EC dysfunction. Impaired eNOS activity can occur at numerous levels, including enzyme uncoupling, post-translational modifications, internalization and decreased expression. Reduced nitric oxide (NO) bioavailability exacerbates oxidative stress, further promoting endothelial dysfunction and injury. The injured ECs may then function as active signal transducers of metabolic, hemodynamic and inflammatory factors that modify the function and morphology of the vessel wall and interact with adjacent cells, which may activate a cascade of inflammatory and proliferative and profibrotic responses in progressive DN. Both pharmacological approaches and potential regenerative therapies hold promise for restoration of impaired endothelial cells in diabetic nephropathy.
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Affiliation(s)
| | - Raymond C Harris
- Division of Nephrology, S3223 MCN, Vanderbilt University School of Medicine, and Nashville Veterans Affairs Hospital, Nashville, TN 37232, USA.
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10
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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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11
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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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12
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Tejero J, Stuehr D. Tetrahydrobiopterin in nitric oxide synthase. IUBMB Life 2013; 65:358-65. [PMID: 23441062 DOI: 10.1002/iub.1136] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 12/25/2012] [Indexed: 11/10/2022]
Abstract
SUMMARY Nitric oxide synthase (NOS) is a critical enzyme for the production of the messenger molecule nitric oxide (NO) from L-arginine. NOS enzymes require tetrahydrobiopterin as a cofactor for NO synthesis. Besides being one of the few enzymes to use this cofactor, the role of tetrahydrobiopterin in NOS catalytic mechanism is different from other enzymes: during the catalytic cycle of NOS, tetrahydrobiopterin forms a radical species that is again reduced, thus effectively regenerating after each NO synthesis cycle. In this review, we summarize our current knowledge about the role of tetrahydrobiopterin in the structure, function, and catalytic mechanism of NOS enzymes.
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Affiliation(s)
- Jesús Tejero
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA
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13
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Feng C. Mechanism of Nitric Oxide Synthase Regulation: Electron Transfer and Interdomain Interactions. Coord Chem Rev 2012; 256:393-411. [PMID: 22523434 PMCID: PMC3328867 DOI: 10.1016/j.ccr.2011.10.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nitric oxide synthase (NOS), a flavo-hemoprotein, tightly regulates nitric oxide (NO) synthesis and thereby its dual biological activities as a key signaling molecule for vasodilatation and neurotransmission at low concentrations, and also as a defensive cytotoxin at higher concentrations. Three NOS isoforms, iNOS, eNOS and nNOS (inducible, endothelial, and neuronal NOS), achieve their key biological functions by tight regulation of interdomain electron transfer (IET) process via interdomain interactions. In particular, the FMN-heme IET is essential in coupling electron transfer in the reductase domain with NO synthesis in the heme domain by delivery of electrons required for O(2) activation at the catalytic heme site. Compelling evidence indicates that calmodulin (CaM) activates NO synthesis in eNOS and nNOS through a conformational change of the FMN domain from its shielded electron-accepting (input) state to a new electron-donating (output) state, and that CaM is also required for proper alignment of the domains. Another exciting recent development in NOS enzymology is the discovery of importance of the the FMN domain motions in modulating reactivity and structure of the catalytic heme active site (in addition to the primary role of controlling the IET processes). In the absence of a structure of full-length NOS, an integrated approach of spectroscopic (e.g. pulsed EPR, MCD, resonance Raman), rapid kinetics (laser flash photolysis and stopped flow) and mutagenesis methods is critical to unravel the molecular details of the interdomain FMN/heme interactions. This is to investigate the roles of dynamic conformational changes of the FMN domain and the docking between the primary functional FMN and heme domains in regulating NOS activity. The recent developments in understanding of mechanisms of the NOS regulation that are driven by the combined approach are the focuses of this review. An improved understanding of the role of interdomain FMN/heme interaction and CaM binding may serve as the basis for the design of new selective inhibitors of NOS isoforms.
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Affiliation(s)
- Changjian Feng
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, NM 87131 (USA) , Tel: 505-925-4326
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PPAR-α Agonist Fenofibrate Upregulates Tetrahydrobiopterin Level through Increasing the Expression of Guanosine 5'-Triphosphate Cyclohydrolase-I in Human Umbilical Vein Endothelial Cells. PPAR Res 2011; 2011:523520. [PMID: 22190909 PMCID: PMC3236356 DOI: 10.1155/2011/523520] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/04/2011] [Accepted: 09/04/2011] [Indexed: 11/17/2022] Open
Abstract
Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide (NO) synthase. Guanosine 5'-triphosphate cyclohydrolase-I (GTPCH-I) is a key limiting enzyme for BH4 synthesis. In the present in vitro study, we investigated whether peroxisome proliferator-activated receptor α (PPAR-α) agonist fenofibrate could recouple eNOS by reversing low-expression of intracellular BH4 in endothelial cells and discussed the potential mechanisms. After human umbilical vein endothelial cells (HUVECs) were treated with lipopolysaccharide (LPS) for 24 hours, the levels of cellular eNOS, BH4 and cell supernatant NO were significantly reduced compared to control group. And the fluorescence intensity of intracellular ROS was significantly increased. But pretreated with fenofibrate (10 umol/L) for 2 hours before cells were induced by LPS, the levels of eNOS, NO, and BH4 were significantly raised compared to LPS treatment alone. ROS production was markedly reduced in fenofibrate group than LPS group. In addition, our results showed that the level of intracellular GTPCH-I detected by western blot was increased in a concentration-dependent manner after being treated with fenofibrate. These results suggested that fenofibrate might help protect endothelial function and against atherosclerosis by increasing level of BH4 and decreasing production of ROS through upregulating the level of intracellular GTPCH-I.
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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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16
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Maréchal A, Mattioli TA, Stuehr DJ, Santolini J. NO synthase isoforms specifically modify peroxynitrite reactivity. FEBS J 2010; 277:3963-73. [DOI: 10.1111/j.1742-4658.2010.07786.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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17
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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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18
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Guan ZW, Haque MM, Wei CC, Garcin ED, Getzoff ED, Stuehr DJ. Lys842 in neuronal nitric-oxide synthase enables the autoinhibitory insert to antagonize calmodulin binding, increase FMN shielding, and suppress interflavin electron transfer. J Biol Chem 2009; 285:3064-75. [PMID: 19948738 DOI: 10.1074/jbc.m109.000810] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal nitric-oxide synthase (nNOS) contains a unique autoinhibitory insert (AI) in its FMN subdomain that represses nNOS reductase activities and controls the calcium sensitivity of calmodulin (CaM) binding to nNOS. How the AI does this is unclear. A conserved charged residue (Lys(842)) lies within a putative CaM binding helix in the middle of the AI. We investigated its role by substituting residues that neutralize (Ala) or reverse (Glu) the charge at Lys(842). Compared with wild type nNOS, the mutant enzymes had greater cytochrome c reductase and NADPH oxidase activities in the CaM-free state, were able to bind CaM at lower calcium concentration, and had lower rates of heme reduction and NO synthesis in one case (K842A). Moreover, stopped-flow spectrophotometric experiments with the nNOS reductase domain indicate that the CaM-free mutants had faster flavin reduction kinetics and had less shielding of their FMN subdomains compared with wild type and no longer increased their level of FMN shielding in response to NADPH binding. Thus, Lys(842) is critical for the known functions of the AI and also enables two additional functions of the AI as newly identified here: suppression of electron transfer to FMN and control of the conformational equilibrium of the nNOS reductase domain. Its effect on the conformational equilibrium probably explains suppression of catalysis by the AI.
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Affiliation(s)
- Zhi-Wen Guan
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
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19
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Davydov R, Sudhamsu J, Lees NS, Crane BR, Hoffman BM. EPR and ENDOR characterization of the reactive intermediates in the generation of NO by cryoreduced oxy-nitric oxide synthase from Geobacillus stearothermophilus. J Am Chem Soc 2009; 131:14493-507. [PMID: 19754116 DOI: 10.1021/ja906133h] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cryoreduction EPR/ENDOR/step-annealing measurements with substrate complexes of oxy-gsNOS (3; gsNOS is nitric oxide synthase from Geobacillus stearothermophilus) confirm that Compound I (6) is the reactive heme species that carries out the gsNOS-catalyzed (Stage I) oxidation of L-arginine to N-hydroxy-L-arginine (NOHA), whereas the active species in the (Stage II) oxidation of NOHA to citrulline and HNO/NO(-) is the hydroperoxy-ferric form (5). When 3 is reduced by tetrahydrobiopterin (BH4), instead of an externally supplied electron, the resulting BH4(+) radical oxidizes HNO/NO(-) to NO. In this report, radiolytic one-electron reduction of 3 and its complexes with Arg, Me-Arg, and NO(2)Arg was shown by EPR and (1)H and (14,15)N ENDOR spectroscopies to generate 5; in contrast, during cryoreduction of 3/NOHA, the peroxo-ferric-gsNOS intermediate (4/NOHA) was trapped. During annealing at 145 K, ENDOR shows that 5/Arg and 5/Me-Arg (but not 5/NO(2)Arg) generate a Stage I primary product species in which the OH group of the hydroxylated substrate is coordinated to Fe(III), characteristic of 6 as the active heme center. Analysis shows that hydroxylation of Arg and Me-Arg is quantitative. Annealing of 4/NOHA at 160 K converts it first to 5/NOHA and then to the Stage II primary enzymatic product. The latter contains Fe(III) coordinated by water, characteristic of 5 as the active heme center. It further contains quantitative amounts of citrulline and HNO/NO(-); the latter reacts with the ferriheme to form the NO-ferroheme upon further annealing. Stage I delivery of the first proton of catalysis to the (unobserved) 4 formed by cryoreduction of 3 involves a bound water that may convey a proton from L-Arg, while the second proton likely derives from the carboxyl side chain of Glu 248 or the heme carboxylates; the process also involves proton delivery by water(s). In the Stage II oxidation of NOHA, the proton that converts 4/NOHA to 5/NOHA likely is derived from NOHA itself, a conclusion supported by the pH invariance of the process. The present results illustrate how the substrate itself modulates the nature and reactivity of intermediates along the monooxygenase reaction pathway.
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Affiliation(s)
- Roman Davydov
- Chemistry Department, Northwestern University, Evanston, Illinois 60208-3113, USA
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20
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Vásquez-Vivar J. Tetrahydrobiopterin, superoxide, and vascular dysfunction. Free Radic Biol Med 2009; 47:1108-19. [PMID: 19628033 PMCID: PMC2852262 DOI: 10.1016/j.freeradbiomed.2009.07.024] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Revised: 06/20/2009] [Accepted: 07/15/2009] [Indexed: 01/06/2023]
Abstract
(6R)-5,6,7,8-Tetrahydrobiopterin (BH(4)) is an endogenously produced pterin that is found widely distributed in mammalian tissues. BH(4) works as a cofactor of aromatic amino acid hydroxylases and nitric oxide synthases. In the vasculature a deficit of BH(4) is implicated in the mechanisms of several diseases including atherosclerosis, hypertension, diabetic vascular disease, and vascular complications from cigarette smoking and environmental pollution. These ill-effects are connected to the ability of BH(4) to regulate reactive oxygen species levels in the endothelium. The possibility of using BH(4) as a therapeutical agent in cardiovascular medicine is becoming more compelling and many biochemical and physiological aspects involved in this application are currently under investigation. This review summarizes our current understanding of BH(4) reactivity and some aspects of cellular production and regulation.
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Affiliation(s)
- Jeannette Vásquez-Vivar
- Department of Biophysics, Free Radical Research Center, Redox Biology Program, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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21
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Latifi R, Bagherzadeh M, de Visser SP. Origin of the correlation of the rate constant of substrate hydroxylation by nonheme iron(IV)-oxo complexes with the bond-dissociation energy of the C-H bond of the substrate. Chemistry 2009; 15:6651-62. [PMID: 19472231 DOI: 10.1002/chem.200900211] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Mononuclear nonheme iron containing systems are versatile and vital oxidants of substrate hydroxylation reactions in many biosystems, whereby the rate constant of hydroxylation correlates with the strength of the C-H bond that is broken in the process. The thermodynamic reason behind these correlations, however, has never been established. In this work results of a series of density functional theory calculations of substrate hydroxylation by a mononuclear nonheme iron(IV)-oxo oxidant with a 2 His/1 Asp structural motif analogous to alpha-ketoglutarate dependent dioxygenases are presented. The calculations show that these oxidants are very efficient and able to hydroxylate strong C-H bonds, whereby the hydrogen abstraction barriers correlate linearly with the strength of the C-H bond of the substrate that is broken. These trends have been rationalized using a valence bond (VB) curve-crossing diagram, which explains the correlation using electron transfer mechanisms in the hydrogen abstraction processes. We also rationalized the subsequent reaction step for radical rebound and show that the barrier is proportional to the electron affinity of the iron(III)-hydroxo intermediate complex. It is shown that nonheme iron(IV)-hydroxo complexes have a larger electron affinity than heme iron(IV)-hydroxo complexes and therefore also experience larger radical rebound barriers, which may have implications for product distributions and rearrangement reactions. Thus, detailed comparisons between heme and nonheme iron(IV)-oxo oxidants reveal the fundamental differences in monoxygenation capabilities of these important classes of oxidants in biosystems and synthetic analogues for the first time and enable us to make predictions of experimental processes.
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Affiliation(s)
- Reza Latifi
- The Manchester Interdisciplinary Biocentre and the School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
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22
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Del Valle-Mondragón L, Tenorio-López FA, Torres-Narváez JC, Zarco-Olvera G, Pastelín-Hernández G. Coronary vasodilator activity of vulgarenol, a sesquiterpene isolated from Magnolia grandiflora, and its possible mechanism. Phytother Res 2009; 23:666-71. [PMID: 19107855 DOI: 10.1002/ptr.2696] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aim of this study was to investigate the biodynamic effects of vulgarenol, a sesquiterpene isolated from Magnolia grandiflora flower petals and its possible mechanism on the Langendorff isolated and perfused heart model. Vulgarenol (5 microm) caused a statistically significant decrease in coronary vascular resistance (15.21 +/- 6.00 dyn s cm(-5) vs 36.80 +/- 5.01 dyn s cm(-5), control group), increased nitric oxide release (223.01 +/- 8.76 pmol/mL vs 61.00 +/- 12.00 pmol/mL, control group) and cyclic guanosine monophosphate accumulation in left ventricular tissue samples (142.17 +/- 8.41 pmol/mg of tissue vs 43.94 +/- 5.00 pmol/mg of tissue, control group). Pre-treatment with 3 microm gadolinium chloride hexahydrate, 100 microm N(omega)-nitro-L-arginine methyl ester hydrochloride, and 10 microm 1H-[1,2,4]oxadiazolo[4,2-a]quinoxalin-1-one significantly abolished the vulgarenol-induced coronary vascular resistance decrease, nitric oxide increased release and cGMP accumulation in left ventricular tissue samples. The results support the fact that nitric oxide and cyclic guanosine monophosphate are likely involved in the endothelium-dependent coronary vasodilation.
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Affiliation(s)
- L Del Valle-Mondragón
- Departamento de Farmacología, Instituto Nacional de Cardiología Ignacio Chávez, Tlalpan, México
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23
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Density functional theory (DFT) and combined quantum mechanical/molecular mechanics (QM/MM) studies on the oxygen activation step in nitric oxide synthase enzymes. Biochem Soc Trans 2009; 37:373-7. [DOI: 10.1042/bst0370373] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In this review paper, we will give an overview of recent theoretical studies on the catalytic cycle(s) of NOS (nitric oxide synthase) enzymes and in particular on the later stages of these cycles where experimental work is difficult due to the short lifetime of intermediates. NOS enzymes are vital for human health and are involved in the biosynthesis of toxic nitric oxide. Despite many experimental efforts in the field, the catalytic cycle of this important enzyme is still surrounded by many unknowns and controversies. Our theoretical studies were focused on the grey zones of the catalytic cycle, where intermediates are short-lived and experimental detection is impossible. Thus combined QM/MM (quantum mechanics/molecular mechanics) as well as DFT (density functional theory) studies on NOS enzymes and active site models have established a novel mechanism of oxygen activation and the conversion of L-arginine into Nω-hydroxo-arginine. Although NOS enzymes show many structural similarities to cytochrome P450 enzymes, it has long been anticipated that therefore they should have a similar catalytic cycle where molecular oxygen binds to a haem centre and is converted into an Fe(IV)-oxo haem(+•) active species (Compound I). Compound I, however, is elusive in the cytochrome P450s as well as in NOS enzymes, but indirect experimental evidence on cytochrome P450 systems combined with theoretical modelling have shown it to be the oxidant responsible for hydroxylation reactions in cytochrome P450 enzymes. By contrast, in the first catalytic cycle of NOS it has been shown that Compound I is first reduced to Compound II before the hydroxylation of arginine. Furthermore, substrate arginine in NOS enzymes appears to have a dual function, namely first as a proton donor in the catalytic cycle to convert the ferric-superoxo into a ferric-hydroperoxo complex and secondly as the substrate that is hydroxylated in the process leading to Nω-hydroxo-arginine.
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24
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de Visser SP, Straganz GD. Why Do Cysteine Dioxygenase Enzymes Contain a 3-His Ligand Motif Rather than a 2His/1Asp Motif Like Most Nonheme Dioxygenases? J Phys Chem A 2009; 113:1835-46. [DOI: 10.1021/jp809700f] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sam P. de Visser
- The Manchester Interdisciplinary Biocenter and the School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom, and Graz University of Technology, Institute of Biotechnology and Biochemical Engineering, Petersgasse 12, A-8010 Graz, Austria
| | - Grit D. Straganz
- The Manchester Interdisciplinary Biocenter and the School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom, and Graz University of Technology, Institute of Biotechnology and Biochemical Engineering, Petersgasse 12, A-8010 Graz, Austria
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25
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Thomas SR, Witting PK, Drummond GR. Redox control of endothelial function and dysfunction: molecular mechanisms and therapeutic opportunities. Antioxid Redox Signal 2008; 10:1713-65. [PMID: 18707220 DOI: 10.1089/ars.2008.2027] [Citation(s) in RCA: 282] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The endothelium is essential for the maintenance of vascular homeostasis. Central to this role is the production of endothelium-derived nitric oxide (EDNO), synthesized by the endothelial isoform of nitric oxide synthase (eNOS). Endothelial dysfunction, manifested as impaired EDNO bioactivity, is an important early event in the development of various vascular diseases, including hypertension, diabetes, and atherosclerosis. The degree of impairment of EDNO bioactivity is a determinant of future vascular complications. Accordingly, growing interest exists in defining the pathologic mechanisms involved. Considerable evidence supports a causal role for the enhanced production of reactive oxygen species (ROS) by vascular cells. ROS directly inactivate EDNO, act as cell-signaling molecules, and promote protein dysfunction, events that contribute to the initiation and progression of endothelial dysfunction. Increasing data indicate that strategies designed to limit vascular ROS production can restore endothelial function in humans with vascular complications. The purpose of this review is to outline the various ways in which ROS can influence endothelial function and dysfunction, describe the redox mechanisms involved, and discuss approaches for preventing endothelial dysfunction that may highlight future therapeutic opportunities in the treatment of cardiovascular disease.
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Affiliation(s)
- Shane R Thomas
- Centre for Vascular Research, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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26
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de Visser SP, Tan LS. Is the bound substrate in nitric oxide synthase protonated or neutral and what is the active oxidant that performs substrate hydroxylation? J Am Chem Soc 2008; 130:12961-74. [PMID: 18774806 DOI: 10.1021/ja8010995] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present here results of a series of density functional theory (DFT) studies on enzyme active site models of nitric oxide synthase (NOS) and address the key steps in the catalytic cycle whereby the substrate (L-arginine) is hydroxylated to N(omega)-hydroxo-arginine. It has been proposed that the mechanism follows a cytochrome P450-type catalytic cycle; however, our calculations find an alternative low energy pathway whereby the bound L-arginine substrate has two important functions in the catalytic cycle, namely first as a proton donor and later as the substrate in the reaction mechanism. Thus, the DFT studies show that the oxo-iron active species (compound I) cannot abstract a proton and neither a hydrogen atom from protonated L-arginine due to the strength of the N-H bonds of the substrate. However, the hydroxylation of neutral arginine by compound I and its one electron reduced form (compound II) requires much lower barriers and is highly exothermic. Detailed analysis of proton transfer mechanisms shows that the basicity of the dioxo dianion and the hydroperoxo-iron (compound 0) intermediates in the catalytic cycle are larger than that of arginine, which makes it likely that protonated arginine donates one of the two protons needed during the first catalytic cycle of NOS. Therefore, DFT predicts that in NOS enzymes arginine binds to the active site in its protonated form, but is deprotonated during the oxygen activation process in the catalytic cycle by either the dioxo dianion species or compound 0. As a result of the low ionization potential of neutral arginine, the actual hydroxylation reaction starts with an initial electron transfer from the substrate to compound I to create compound II followed by a concerted hydrogen abstraction/radical rebound from the substrate. These studies indicate that compound II is the actual oxidant in NOS enzymes that performs the hydroxylation reaction of arginine, which is in sharp contrast with the cytochromes P450 where compound II was shown to be a sluggish oxidant. This is the first example of an enzyme where compound II is able to participate in the reaction mechanism. Moreover, arginine hydroxylation by NOS enzymes is catalyzed in a significantly different way from the cytochromes P450 although the active sites of the two enzyme classes are very similar in structure. Detailed studies of environmental effects on the reaction mechanism show that environmental perturbations as appear in the protein have little effect and do not change the energies of the reaction. Finally, a valence bond curve crossing model has been set up to explain the obtained reaction mechanisms for the hydrogen abstraction processes in P450 and NOS enzymes.
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Affiliation(s)
- Sam P de Visser
- Manchester Interdisciplinary Biocenter and the School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom.
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27
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Grinkova YV, Denisov IG, Waterman MR, Arase M, Kagawa N, Sligar SG. The ferrous-oxy complex of human aromatase. Biochem Biophys Res Commun 2008; 372:379-82. [PMID: 18482580 DOI: 10.1016/j.bbrc.2008.05.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 05/05/2008] [Indexed: 10/22/2022]
Abstract
In this communication, we document the self-assembly of heterologously expressed truncated human aromatase (CYP19) into nanometer scale phospholipids bilayers (Nanodiscs). The resulting P450 CYP19 preparation is stable and can tightly associate with the substrate androstenedione to form a nearly complete high-spin ferric protein. Ferrous CYP19 in Nanodiscs was mixed anaerobically in a rapid-scan stopped-flow with atmospheric dioxygen and the formation of the ferrous-oxy complex observed. First order decay of the oxy-complex to release superoxide and regenerate the ferric enzyme was monitored kinetically. Surprisingly, the ferrous-oxy complex of aromatase is more stable than that of hepatic CYP3A4, opening the path to precisely determine the biochemical and biophysical properties of the reaction cycle intermediates in this important human drug target.
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Affiliation(s)
- Yelena V Grinkova
- Department of Biochemistry, Center for Biophysics and Computational Biology, University of Illinois, Urbana, IL 61801, USA
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28
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Glazer EC, Nguyen YHL, Gray HB, Goodin DB. Probing inducible nitric oxide synthase with a pterin-ruthenium(II) sensitizer wire. Angew Chem Int Ed Engl 2008; 47:898-901. [PMID: 18085539 DOI: 10.1002/anie.200703743] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Edith C Glazer
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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29
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Protein electrodes with direct electrochemical communication. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2008; 109:19-64. [PMID: 17928972 DOI: 10.1007/10_2007_083] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
Electrochemistry using direct electron transfer between an electrode and a protein or an enzyme has developed into a means for studying biological redox reactions and for bioanalytics, biosynthesis and bioenergetics. This review summarizes recent work on direct protein electrochemistry with special emphasis on our results in bioelectrocatalysis using isolated enzymes and enzyme-protein couples.
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Glazer E, Nguyen Y, Gray H, Goodin D. Probing Inducible Nitric Oxide Synthase with a Pterin–Ruthenium(II) Sensitizer Wire. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200703743] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Besides nitric oxide (NO), NO synthases (NOS) also produce superoxide ((*)O(2)()), a primary reactive oxygen species involved in both cell injury and signaling. Neuronal NOS was first found to produce (*)O(2)(-) in vitro. Subsequent studies revealed (*)O(2)(-) generation as a common property of all NOS isoforms. Although NOS was originally shown to produce (*)O(2)(-) under defined conditions such as substrate or cofactor depletion, recent enzymatic studies found that the reduction of oxygen to (*)O(2)(-) is an obligatory step in NO synthesis. Tetrahydrobiopterin appears to play a key role in preventing (*)O(2)(-) release from the NOS oxygenase domain. On the other hand, the NOS reductase domain is also capable of producing significant amounts of (*)O(2)(-). Increasing evidence demonstrates that (*)O(2)(-) generation is involved in both physiological and pathological actions of NOS.
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Affiliation(s)
- Yong Xia
- Davis Heart and Lung Research Institute, Division of Cardiovascular Medicine, Department of Molecular and Cellular Biochemistry, The Ohio State University Medical Center, Columbus, Ohio 43210, USA.
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Iyanagi T. Molecular mechanism of phase I and phase II drug-metabolizing enzymes: implications for detoxification. ACTA ACUST UNITED AC 2007; 260:35-112. [PMID: 17482904 DOI: 10.1016/s0074-7696(06)60002-8] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Enzymes that catalyze the biotransformation of drugs and xenobiotics are generally referred to as drug-metabolizing enzymes (DMEs). DMEs can be classified into two main groups: oxidative or conjugative. The NADPH-cytochrome P450 reductase (P450R)/cytochrome P450 (P450) electron transfer systems are oxidative enzymes that mediate phase I reactions, whereas the UDP-glucuronosyltransferases (UGTs) are conjugative enzymes that mediate phase II enzymes. Both enzyme systems are localized to the endoplasmic reticulum (ER) where a number of drugs are sequentially metabolized. DMEs, including P450s and UGTs, generally have a highly plastic active site that can accommodate a wide variety of substrates. The P450 and UGT genes constitute a supergene family, in which UGT proteins are encoded by distinct genes and a complex gene. Both the P450 and UGT genes have evolved to diversify their functions. This chapter reviews advances in understanding the structure and function of the P450R/P450 and UGT enzyme systems. In particular, the coordinate biotransformation of xenobiotics by phase I and II enzymes in the ER membrane is examined.
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Affiliation(s)
- Takashi Iyanagi
- Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
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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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Gorren ACF, Mayer B. Nitric-oxide synthase: A cytochrome P450 family foster child. Biochim Biophys Acta Gen Subj 2007; 1770:432-45. [PMID: 17014963 DOI: 10.1016/j.bbagen.2006.08.019] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Accepted: 08/25/2006] [Indexed: 11/28/2022]
Abstract
Nitric-oxide synthase (NOS), the enzyme responsible for mammalian NO generation, is no cytochrome P450, but there are striking similarities between both enzymes. First and foremost, both are heme-thiolate proteins, employing the same prosthetic group to perform similar chemistry. Moreover, they share the same redox partner, a diflavoprotein reductase, which in the case of NOS is incorporated with the oxygenase in one polypeptide chain. There are, however, also conspicuous differences, such as the presence in NOS of the additional cofactor tetrahydrobiopterin, which is applied as an auxiliary electron donor to prevent decay of the oxyferrous complex to ferric heme and superoxide. In this review similarities and differences between NOS and cytochrome P450 are analyzed in an attempt to explain why NOS requires BH4 and why NO synthesis is not catalyzed by a member of the cytochrome P450 family.
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Affiliation(s)
- Antonius C F Gorren
- Department of Pharmacology und Toxicology, Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
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Chartier F, Couture M. Interactions between substrates and the haem-bound nitric oxide of ferric and ferrous bacterial nitric oxide synthases. Biochem J 2007; 401:235-45. [PMID: 16970546 PMCID: PMC1698664 DOI: 10.1042/bj20060913] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 09/11/2006] [Accepted: 09/14/2006] [Indexed: 11/17/2022]
Abstract
We report here the resonance Raman spectra of the FeIII-NO and FeII-NO complexes of the bacterial NOSs (nitric oxide synthases) from Staphylococcus aureus and Bacillus subtilis. The haem-NO complexes of these bacterial NOSs displayed Fe-N-O frequencies similar to those of the mammalian NOSs, in presence and absence of L-arginine, indicating that haem-bound NO and L-arginine had similar haem environments in bacterial and mammalian NOSs. The only notable difference between the two types of NOS was the lack of change in Fe-N-O frequencies of the FeIII-NO complexes upon (6R) 5,6,7,8-tetrahydro-L-biopterin binding to bacterial NOSs. We report, for the first time, the characterization of NO complexes with NOHA (N(omega)-hydroxy-L-arginine), the substrate used in the second half of the catalytic cycle of NOSs. In the FeIII-NO complexes, both L-arginine and NOHA induced the Fe-N-O bending mode at nearly the same frequency as a result of a steric interaction between the substrates and the haem-bound NO. However, in the FeII-NO complexes, the Fe-N-O bending mode was not observed and the nu(Fe-NO) mode displayed a 5 cm(-1) higher frequency in the complex with NOHA than in the complex with L-arginine as a result of direct interactions that probably involve hydrogen bonds. The different behaviour of the substrates in the FeII-NO complexes thus reveal that the interactions between haem-bound NO and the substrates are finely tuned by the geometry of the Fe-ligand structure and are relevant to the use of the FeII-NO complex as a model of the oxygenated complex of NOSs.
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Key Words
- l-arginine
- haem
- nω-hydroxy-l-arginine (noha)
- nitric oxide synthase (nos)
- resonance raman spectroscopy
- 5c, 5-co-ordinated
- 6c, 6-co-ordinated
- bsnos, bacillus subtilis nitric oxide synthase
- drnos, deinococcus radiodurans nos
- dtt, dithiothreitol
- enos, endothelial nos
- feiii, ferric form
- feii, ferrous form
- gsnos, geobacillus stearothermophilus nos
- h4b, (6r) 5,6,7,8-tetrahydro-l-biopterin
- inos, inducible nos
- nnos, neuronal nos
- noha, nω-hydroxy-l-arginine
- nosox, oxygenase domain of nos
- sanos, staphylococcus aureus nos
- thf, tetrahydrofolate
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Affiliation(s)
- François J. M. Chartier
- Département de Biochimie et de Microbiologie, and Centre de Recherche sur la fonction, la structure et l'ingénierie des protéines (CREFSIP), Université Laval, Québec, Canada
| | - Manon Couture
- Département de Biochimie et de Microbiologie, and Centre de Recherche sur la fonction, la structure et l'ingénierie des protéines (CREFSIP), Université Laval, Québec, Canada
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Munro AW, Girvan HM, McLean KJ. Cytochrome P450--redox partner fusion enzymes. Biochim Biophys Acta Gen Subj 2006; 1770:345-59. [PMID: 17023115 DOI: 10.1016/j.bbagen.2006.08.018] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 08/23/2006] [Accepted: 08/25/2006] [Indexed: 12/23/2022]
Abstract
The cytochromes P450 (P450s) are a broad class of heme b-containing mono-oxygenase enzymes. The vast majority of P450s catalyse reductive scission of molecular oxygen using electrons usually derived from coenzymes (NADH and NADPH) and delivered from redox partner proteins. Evolutionary advantages may be gained by fusion of one or more redox partners to the P450 enzyme in terms of e.g. catalytic efficiency. This route was taken by the well characterized flavocytochrome P450(BM3) system (CYP102A1) from Bacillus megaterium, in which soluble P450 and cytochrome P450 reductase enzymes are covalently linked to produce a highly efficient electron transport system for oxygenation of fatty acids and related molecules. However, genome analysis and ongoing enzyme characterization has revealed that there are a number of other novel classes of P450-redox partner fusion enzymes distributed widely in prokaryotes and eukaryotes. This review examines our current state of knowledge of the diversity of these fusion proteins and explores their structural composition and evolutionary origins.
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Affiliation(s)
- Andrew W Munro
- Manchester Interdisciplinary Biocentre, School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester, M1 7ND, UK.
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Garner D, McMaster J, Raven E, Walton P. Dalton Discussion No. 8. Metals: centres of biological activity. Dalton Trans 2005:3372-4. [PMID: 16234913 DOI: 10.1039/b513314a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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