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Nemeikaitė-Čėnienė A, Misevičienė L, Marozienė A, Jonušienė V, Čėnas N. Enzymatic Redox Properties and Cytotoxicity of Irreversible Nitroaromatic Thioredoxin Reductase Inhibitors in Mammalian Cells. Int J Mol Sci 2023; 24:12460. [PMID: 37569833 PMCID: PMC10419047 DOI: 10.3390/ijms241512460] [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: 06/28/2023] [Revised: 07/20/2023] [Accepted: 08/03/2023] [Indexed: 08/13/2023] Open
Abstract
NADPH:thioredoxin reductase (TrxR) is considered a potential target for anticancer agents. Several nitroheterocyclic sulfones, such as Stattic and Tri-1, irreversibly inhibit TrxR, which presumably accounts for their antitumor activity. However, it is necessary to distinguish the roles of enzymatic redox cycling, an inherent property of nitroaromatics (ArNO2), and the inhibition of TrxR in their cytotoxicity. In this study, we calculated the previously unavailable values of single-electron reduction potentials of known inhibitors of TrxR (Stattic, Tri-1, and 1-chloro-2,4-dinitrobenzene (CDNB)) and inhibitors identified (nitrofuran NSC697923 and nitrobenzene BTB06584). These calculations were according to the rates of their enzymatic single-electron reduction (PMID: 34098820). This enabled us to compare their cytotoxicity with that of model redox cycling ArNO2. In MH22a and HCT-116 cells, Tri-1, Stattic, CDNB, and NSC697023 possessed at least 10-fold greater cytotoxicity than can be expected from their redox cycling activity. This may be related to TrxR inhibition. The absence of enhanced cytotoxicity in BTB06548 may be attributed to its instability. Another known inhibitor of TrxR, tetryl, also did not possess enhanced cytotoxicity, probably because of its detoxification by DT-diaphorase (NQO1). Apart from the reactions with NQO1, the additional mechanisms influencing the cytotoxicity of the examined inhibitors of TrxR are their reactions with cytochromes P-450. Furthermore, some inhibitors, such as Stattic and NSC697923, may also inhibit glutathione reductase. We suggest that these data may be instrumental in the search for TrxR inhibitors with enhanced cytotoxic/anticancer activity.
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Affiliation(s)
- Aušra Nemeikaitė-Čėnienė
- Department of Immunology of State Research Institute Center for Innovative Medicine, Santariškiu˛ St. 5, LT-08406 Vilnius, Lithuania;
| | - Lina Misevičienė
- Department of Xenobiotics Biochemistry, Institute of Biochemistry of Vilnius University, Sauletekio 7, LT-10257 Vilnius, Lithuania; (L.M.); (A.M.)
| | - Audronė Marozienė
- Department of Xenobiotics Biochemistry, Institute of Biochemistry of Vilnius University, Sauletekio 7, LT-10257 Vilnius, Lithuania; (L.M.); (A.M.)
| | - Violeta Jonušienė
- Department of Biochemistry and Molecular Biology, Institute of Biosciences of Vilnius University, Sauletekio 7, LT-10257 Vilnius, Lithuania;
| | - Narimantas Čėnas
- Department of Xenobiotics Biochemistry, Institute of Biochemistry of Vilnius University, Sauletekio 7, LT-10257 Vilnius, Lithuania; (L.M.); (A.M.)
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Stoyanov S, Yancheva D, Velcheva E, Stamboliyska B. Anion and radical anion products of flutamide studied by IR spectra and density functional calculations. J Mol Struct 2023. [DOI: 10.1016/j.molstruc.2022.133927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Šarlauskas J, Stankevičiūtė J, Tamulienė J. An Efficient Synthesis and Preliminary Investigation of Novel 1,3-Dihydro- 2H-benzimidazol-2-one Nitro and Nitramino Derivatives. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8330. [PMID: 36499818 PMCID: PMC9737477 DOI: 10.3390/ma15238330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/17/2022] [Accepted: 11/21/2022] [Indexed: 06/17/2023]
Abstract
The preparation and properties of a series of novel 1,3-dihydro-2H-benzimidazol-2-one nitro and nitramino derivatives are described. A detailed crystal structure of one of the obtained compounds, 4,5,6-trinitro-1,3-dihydro-2H-benzimidazol-2-one (TriNBO), was characterized using low temperature single crystal X-ray diffraction, namely an orthorhombic yellow prism, space group 'P 2 21 21', experimental crystal density 1.767 g/cm3 (at 173 K). Methyl analog, 5-Me-TriNBO-monoclinic red plates, space group, P 21/c, crystal density 1.82 g/cm3. TriNBO contains one activated nitro group at the fifth position, which was used for the nucleophilic substitution in the aminolysis reactions with three monoalkylamines (R=CH3, C2H5, (CH2)2CH3) and ethanolamine. The 5-R-aminoderivatives were further nitrated with N2O5/ HNO3 and resulted in a new group of appropriate nitramines: 1,3-dihydro-2H-5-R-N(NO2)-4,6-dinitrobenzimidazol-2-ones. Thermal analysis (TGA) of three selected representatives was performed. The new compounds possess a high melting point (200-315 °C) and thermal stability and can find a potential application as new thermostable energetic materials. Some calculated preliminary energetic characteristics show that TriNBO, 5-Me-TriNBO, 5-methylnitramino-1,3-dihydro-2H-4,6-dinitrobenzimidazol-2-one, and 5-nitratoethylnitramino-1,3-dihydro-2H-4,6-dinitrobenzimidazol-2-one possess increased energetic characteristics in comparison with TNT and tetryl. The proposed nitrocompounds may find potential applications as thermostable high-energy materials.
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Affiliation(s)
- Jonas Šarlauskas
- Life Sciences Centre, Department of Xenobiotic Biochemistry, Institute of Biochemistry, Vilnius University, Sauletekio av. 7, 01513 Vilnius, Lithuania
| | - Jonita Stankevičiūtė
- Life Sciences Centre, Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Vilnius University, Sauletekio av. 7, 01513 Vilnius, Lithuania
| | - Jelena Tamulienė
- Physics Faculty, Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio av. 3, 01513 Vilnius, Lithuania
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Targeting HIF-1α Function in Cancer through the Chaperone Action of NQO1: Implications of Genetic Diversity of NQO1. J Pers Med 2022; 12:jpm12050747. [PMID: 35629169 PMCID: PMC9146583 DOI: 10.3390/jpm12050747] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 04/25/2022] [Indexed: 02/04/2023] Open
Abstract
HIF-1α is a master regulator of oxygen homeostasis involved in different stages of cancer development. Thus, HIF-1α inhibition represents an interesting target for anti-cancer therapy. It was recently shown that the HIF-1α interaction with NQO1 inhibits proteasomal degradation of the former, thus suggesting that targeting the stability and/or function of NQO1 could lead to the destabilization of HIF-1α as a therapeutic approach. Since the molecular interactions of NQO1 with HIF-1α are beginning to be unraveled, in this review we discuss: (1) Structure–function relationships of HIF-1α; (2) our current knowledge on the intracellular functions and stability of NQO1; (3) the pharmacological modulation of NQO1 by small ligands regarding function and stability; (4) the potential effects of genetic variability of NQO1 in HIF-1α levels and function; (5) the molecular determinants of NQO1 as a chaperone of many different proteins including cancer-associated factors such as HIF-1α, p53 and p73α. This knowledge is then further discussed in the context of potentially targeting the intracellular stability of HIF-1α by acting on its chaperone, NQO1. This could result in novel anti-cancer therapies, always considering that the substantial genetic variability in NQO1 would likely result in different phenotypic responses among individuals.
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Giovannucci TA, Salomons FA, Haraldsson M, Elfman LHM, Wickström M, Young P, Lundbäck T, Eirich J, Altun M, Jafari R, Gustavsson AL, Johnsen JI, Dantuma NP. Inhibition of the ubiquitin-proteasome system by an NQO1-activatable compound. Cell Death Dis 2021; 12:914. [PMID: 34615851 PMCID: PMC8494907 DOI: 10.1038/s41419-021-04191-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 09/03/2021] [Accepted: 09/16/2021] [Indexed: 11/10/2022]
Abstract
Malignant cells display an increased sensitivity towards drugs that reduce the function of the ubiquitin-proteasome system (UPS), which is the primary proteolytic system for destruction of aberrant proteins. Here, we report on the discovery of the bioactivatable compound CBK77, which causes an irreversible collapse of the UPS, accompanied by a general accumulation of ubiquitylated proteins and caspase-dependent cell death. CBK77 caused accumulation of ubiquitin-dependent, but not ubiquitin-independent, reporter substrates of the UPS, suggesting a selective effect on ubiquitin-dependent proteolysis. In a genome-wide CRISPR interference screen, we identified the redox enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1) as a critical mediator of CBK77 activity, and further demonstrated its role as the compound bioactivator. Through affinity-based proteomics, we found that CBK77 covalently interacts with ubiquitin. In vitro experiments showed that CBK77-treated ubiquitin conjugates were less susceptible to disassembly by deubiquitylating enzymes. In vivo efficacy of CBK77 was validated by reduced growth of NQO1-proficient human adenocarcinoma cells in nude mice treated with CBK77. This first-in-class NQO1-activatable UPS inhibitor suggests that it may be possible to exploit the intracellular environment in malignant cells for leveraging the impact of compounds that impair the UPS.
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Affiliation(s)
- Tatiana A Giovannucci
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, Stockholm, Sweden
| | - Florian A Salomons
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, Stockholm, Sweden
| | - Martin Haraldsson
- Chemical Biology Consortium Sweden (CBCS), Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Solna, Stockholm, Sweden
| | - Lotta H M Elfman
- Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - Malin Wickström
- Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - Patrick Young
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, Stockholm, Sweden
| | - Thomas Lundbäck
- Chemical Biology Consortium Sweden (CBCS), Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Solna, Stockholm, Sweden
- Mechanistic & Structural Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Jürgen Eirich
- Science for Life Laboratory, Department of Oncology-Pathology, Clinical Proteomics Mass Spectrometry, Karolinska Institutet, Solna, Stockholm, Sweden
- Science for Life Laboratory, Department of Medical Biochemistry and Biophysics (MBB), Karolinska Institutet, Solna, Stockholm, Sweden
- Institute of Plant Biology and Biotechnology, University of Muenster, 48143, Muenster, Germany
| | - Mikael Altun
- Science for Life Laboratory, Department of Laboratory Medicine, Karolinska Institutet, Solna, Stockholm, Sweden
| | - Rozbeh Jafari
- Science for Life Laboratory, Department of Oncology-Pathology, Clinical Proteomics Mass Spectrometry, Karolinska Institutet, Solna, Stockholm, Sweden
| | - Anna-Lena Gustavsson
- Chemical Biology Consortium Sweden (CBCS), Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Solna, Stockholm, Sweden
| | - John Inge Johnsen
- Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - Nico P Dantuma
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, Stockholm, Sweden.
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Čėnas N, Nemeikaitė-Čėnienė A, Kosychova L. Single- and Two-Electron Reduction of Nitroaromatic Compounds by Flavoenzymes: Mechanisms and Implications for Cytotoxicity. Int J Mol Sci 2021; 22:ijms22168534. [PMID: 34445240 PMCID: PMC8395237 DOI: 10.3390/ijms22168534] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 07/30/2021] [Accepted: 08/04/2021] [Indexed: 12/14/2022] Open
Abstract
Nitroaromatic compounds (ArNO2) maintain their importance in relation to industrial processes, environmental pollution, and pharmaceutical application. The manifestation of toxicity/therapeutic action of nitroaromatics may involve their single- or two-electron reduction performed by various flavoenzymes and/or their physiological redox partners, metalloproteins. The pivotal and still incompletely resolved questions in this area are the identification and characterization of the specific enzymes that are involved in the bioreduction of ArNO2 and the establishment of their contribution to cytotoxic/therapeutic action of nitroaromatics. This review addresses the following topics: (i) the intrinsic redox properties of ArNO2, in particular, the energetics of their single- and two-electron reduction in aqueous medium; (ii) the mechanisms and structure-activity relationships of reduction in ArNO2 by flavoenzymes of different groups, dehydrogenases-electrontransferases (NADPH:cytochrome P-450 reductase, ferredoxin:NADP(H) oxidoreductase and their analogs), mammalian NAD(P)H:quinone oxidoreductase, bacterial nitroreductases, and disulfide reductases of different origin (glutathione, trypanothione, and thioredoxin reductases, lipoamide dehydrogenase), and (iii) the relationships between the enzymatic reactivity of compounds and their activity in mammalian cells, bacteria, and parasites.
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Affiliation(s)
- Narimantas Čėnas
- Institute of Biochemistry of Vilnius University, Saulėtekio 7, LT-10257 Vilnius, Lithuania;
- Correspondence: ; Tel.: +370-5-223-4392
| | - Aušra Nemeikaitė-Čėnienė
- State Research Institute Center for Innovative Medicine, Santariškių St. 5, LT-08406 Vilnius, Lithuania;
| | - Lidija Kosychova
- Institute of Biochemistry of Vilnius University, Saulėtekio 7, LT-10257 Vilnius, Lithuania;
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Beaver SK, Mesa-Torres N, Pey AL, Timson DJ. NQO1: A target for the treatment of cancer and neurological diseases, and a model to understand loss of function disease mechanisms. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:663-676. [PMID: 31091472 DOI: 10.1016/j.bbapap.2019.05.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 05/07/2019] [Accepted: 05/09/2019] [Indexed: 01/08/2023]
Abstract
NAD(P)H quinone oxidoreductase 1 (NQO1) is a multi-functional protein that catalyses the reduction of quinones (and other molecules), thus playing roles in xenobiotic detoxification and redox balance, and also has roles in stabilising apoptosis regulators such as p53. The structure and enzymology of NQO1 is well-characterised, showing a substituted enzyme mechanism in which NAD(P)H binds first and reduces an FAD cofactor in the active site, assisted by a charge relay system involving Tyr-155 and His-161. Protein dynamics play important role in physio-pathological aspects of this protein. NQO1 is a good target to treat cancer due to its overexpression in cancer cells. A polymorphic form of NQO1 (p.P187S) is associated with increased cancer risk and certain neurological disorders (such as multiple sclerosis and Alzheimer´s disease), possibly due to its roles in the antioxidant defence. p.P187S has greatly reduced FAD affinity and stability, due to destabilization of the flavin binding site and the C-terminal domain, which leading to reduced activity and enhanced degradation. Suppressor mutations partially restore the activity of p.P187S by local stabilization of these regions, and showing long-range allosteric communication within the protein. Consequently, the correction of NQO1 misfolding by pharmacological chaperones is a viable strategy, which may be useful to treat cancer and some neurological conditions, targeting structural spots linked to specific disease-mechanisms. Thus, NQO1 emerges as a good model to investigate loss of function mechanisms in genetic diseases as well as to improve strategies to discriminate between neutral and pathogenic variants in genome-wide sequencing studies.
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Affiliation(s)
- Sarah K Beaver
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Lewes Road, Brighton BN2 4GJ, UK
| | - Noel Mesa-Torres
- Department of Physical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, 18071, Spain
| | - Angel L Pey
- Department of Physical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, 18071, Spain.
| | - David J Timson
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Lewes Road, Brighton BN2 4GJ, UK.
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NAD(P)H quinone oxidoreductase (NQO1): an enzyme which needs just enough mobility, in just the right places. Biosci Rep 2019; 39:BSR20180459. [PMID: 30518535 PMCID: PMC6328894 DOI: 10.1042/bsr20180459] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 11/26/2018] [Accepted: 11/27/2018] [Indexed: 12/23/2022] Open
Abstract
NAD(P)H quinone oxidoreductase 1 (NQO1) catalyses the two electron reduction of quinones and a wide range of other organic compounds. Its physiological role is believed to be partly the reduction of free radical load in cells and the detoxification of xenobiotics. It also has non-enzymatic functions stabilising a number of cellular regulators including p53. Functionally, NQO1 is a homodimer with two active sites formed from residues from both polypeptide chains. Catalysis proceeds via a substituted enzyme mechanism involving a tightly bound FAD cofactor. Dicoumarol and some structurally related compounds act as competitive inhibitors of NQO1. There is some evidence for negative cooperativity in quinine oxidoreductases which is most likely to be mediated at least in part by alterations to the mobility of the protein. Human NQO1 is implicated in cancer. It is often over-expressed in cancer cells and as such is considered as a possible drug target. Interestingly, a common polymorphic form of human NQO1, p.P187S, is associated with an increased risk of several forms of cancer. This variant has much lower activity than the wild-type, primarily due to its substantially reduced affinity for FAD which results from lower stability. This lower stability results from inappropriate mobility of key parts of the protein. Thus, NQO1 relies on correct mobility for normal function, but inappropriate mobility results in dysfunction and may cause disease.
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Kwon J, Cho EM, Nandhakumar P, Yang SI, Yang H. Rapid and Sensitive Detection of Aspergillus niger Using a Single-Mediator System Combined with Redox Cycling. Anal Chem 2018; 90:13491-13497. [PMID: 30403470 DOI: 10.1021/acs.analchem.8b03417] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Rapid and sensitive mold detection is becoming increasingly important, especially in indoor environments. Common mold detection methods based on double-mediated electron transfer between an electrode and molds are not highly sensitive and reproducible, although they are rapid and simple. Here, we report a sensitive and reproducible detection method specific to Aspergillus niger ( A. niger), based on a single-mediator system combined with electrochemical-chemical (EC) redox cycling. Intracellular NAD(P)H-oxidizing enzymes in molds can convert electro-inactive hydroxy-nitro(so)arenes into electro-active hydroxy-aminoarenes. Since the membrane and wall of A. niger is well permeable to both a substrate (4-nitro-1-naphthol) and a reduced product (4-amino-1-naphthol) in tris buffer (pH 7.5) solution, the electrochemical signal is increased in the presence of A. niger due to two reactions: (i) enzymatic reduction of the substrate to the reduced product and (ii) electrochemical oxidation of the reduced product to an oxidized product. When a reducing agent (NADH) is present in the solution, the oxidized product is reduced back to the reduced product and then electrochemically reoxidized. This EC redox cycling significantly amplifies the electrochemical signal. Moreover, the background level is low and highly reproducible because the substrate and the reducing agent are electro-inactive at an applied potential of 0.20 V. The calculated detection limit for A. niger in a common double-mediator system consisting of Fe(CN)63- and menadione is ∼2 × 104 colony-forming unit (CFU)/mL, but the detection limit in the single-mediator system combined with EC redox cycling is ∼2 × 103 CFU/mL, indicating that the newly developed single-mediator system is more sensitive. Importantly, the detection method requires only an incubation period of 10 min and does not require a washing step, an electrode modification step, or a specific probe.
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Affiliation(s)
- Jungwook Kwon
- Department of Chemistry and Chemistry Institute for Functional Materials , Pusan National University , Busan 46241 , Korea
| | - Eun-Min Cho
- Department of Applied Chemistry , Kyung Hee University , Yongin 17104 , Korea
| | - Ponnusamy Nandhakumar
- Department of Chemistry and Chemistry Institute for Functional Materials , Pusan National University , Busan 46241 , Korea
| | - Sung Ik Yang
- Department of Applied Chemistry , Kyung Hee University , Yongin 17104 , Korea
| | - Haesik Yang
- Department of Applied Chemistry , Kyung Hee University , Yongin 17104 , Korea
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Kang C, Kang J, Lee NS, Yoon YH, Yang H. DT-Diaphorase as a Bifunctional Enzyme Label That Allows Rapid Enzymatic Amplification and Electrochemical Redox Cycling. Anal Chem 2017; 89:7974-7980. [PMID: 28696095 DOI: 10.1021/acs.analchem.7b01223] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The most common enzyme labels in enzyme-linked immunosorbent assays are alkaline phosphatase and horseradish peroxidase, which, however, have some limitations for use in electrochemical immunosensors. This Article reports that the small and thermostable DT-diaphorase (DT-D) and electrochemically inactive 4-nitroso-1-naphthol (4-NO-1-N) can be used as a bifunctional enzyme label and a rapidly reacting substrate, respectively, for electrochemical immunosensors. This enzyme-substrate combination allows high signal amplification via rapid enzymatic amplification and electrochemical redox cycling. DT-D can convert an electrochemically inactive nitroso or nitro compound into an electrochemically active amine compound, which can then be involved in electrochemical-chemical (EC) and electrochemical-enzymatic (EN) redox cycling. Six nitroso and nitro compounds are tested in terms of signal-to-background ratio. Among them, 4-NO-1-N exhibits the highest signal-to-background ratio. The electrochemical immunosensor using DT-D and 4-NO-1-N detects parathyroid hormone (PTH) in phosphate-buffered saline containing bovine serum albumin over a wide range of concentrations with a low detection limit of 2 pg/mL. When the PTH concentration in clinical serum samples is measured using the developed immunosensor, the calculated concentrations are in good agreement with the concentrations obtained using a commercial instrument. Thus, the use of DT-D as an enzyme label is highly promising for sensitive electrochemical detection and point-of-care testing.
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Affiliation(s)
- Cheolho Kang
- Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University , Busan 46241, Korea
| | - Juyeon Kang
- Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University , Busan 46241, Korea
| | | | | | - Haesik Yang
- Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University , Busan 46241, Korea
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Bae J, McNamara LE, Nael MA, Mahdi F, Doerksen RJ, Bidwell GL, Hammer NI, Jo S. Nitroreductase-triggered activation of a novel caged fluorescent probe obtained from methylene blue. Chem Commun (Camb) 2016; 51:12787-90. [PMID: 26165999 DOI: 10.1039/c5cc03824c] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A near-infrared fluorescent probe based on methylene blue (p-NBMB) was developed for the detection of nitroreductase. Conjugating methylene blue with a p-nitrobenzyl moiety enables it to be activated by nitroreductase-catalyzed 1,6-elimination, resulting in the release of an active methylene blue fluorophore.
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Affiliation(s)
- Jungeun Bae
- Department of Pharmaceutics and Drug Delivery, School of Pharmacy, The University of Mississippi, University, MS 38677, USA.
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12
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Megarity CF, Looi HK, Timson DJ. The Saccharomyces cerevisiae quinone oxidoreductase Lot6p: stability, inhibition and cooperativity. FEMS Yeast Res 2014; 14:797-807. [PMID: 24866129 DOI: 10.1111/1567-1364.12167] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 05/13/2014] [Accepted: 05/22/2014] [Indexed: 11/28/2022] Open
Abstract
Lot6p (EC 1.5.1.39; Ylr011wp) is the sole quinone oxidoreductase in the budding yeast, Saccharomyces cerevisiae. Using hexahistidine tagged, recombinant Lot6p, we determined the steady-state enzyme kinetic parameters with both NADH and NADPH as electron donors; no cooperativity was observed with these substrates. The NQO1 inhibitor curcumin, the NQO2 inhibitor resveratrol, the bacterial nitroreductase inhibitor nicotinamide and the phosphate mimic vanadate all stabilise the enzyme towards thermal denaturation as judged by differential scanning fluorimetry. All except vanadate have no observable effect on the chemical cross-linking of the two subunits of the Lot6p dimer. These compounds all inhibit Lot6p's oxidoreductase activity, and all except nicotinamide exhibit negative cooperativity. Molecular modelling suggests that curcumin, resveratrol and nicotinamide all bind over the isoalloxazine ring of the FMN cofactor in Lot6p. Resveratrol was predicted to contact an α-helix that links the two active sites. Mutation of Gly-142 (which forms part of this helix) to serine does not greatly affect the thermal stability of the enzyme. However, this variant shows less cooperativity towards resveratrol than the wild type. This suggests a plausible hypothesis for the transmission of information between the subunits and, thus, the molecular mechanism of negative cooperativity in Lot6p.
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Affiliation(s)
- Clare F Megarity
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, UK
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13
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Megarity CF, Gill JRE, Caraher MC, Stratford IJ, Nolan KA, Timson DJ. The two common polymorphic forms of human NRH-quinone oxidoreductase 2 (NQO2) have different biochemical properties. FEBS Lett 2014; 588:1666-72. [PMID: 24631540 PMCID: PMC4045209 DOI: 10.1016/j.febslet.2014.02.063] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/18/2014] [Accepted: 02/21/2014] [Indexed: 10/25/2022]
Abstract
There are two common forms of NRH-quinone oxidoreductase 2 (NQO2) in the human population resulting from SNP rs1143684. One has phenylalanine at position 47 (NQO2-F47) and the other leucine (NQO2-L47). Using recombinant proteins, we show that these variants have similar steady state kinetic parameters, although NQO2-L47 has a slightly lower specificity constant. NQO2-L47 is less stable towards proteolytic digestion and thermal denaturation than NQO2-F47. Both forms are inhibited by resveratrol, but NQO2-F47 shows negative cooperativity with this inhibitor. Thus these data demonstrate, for the first time, clear biochemical differences between the variants which help explain previous biomedical and epidemiological findings.
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Affiliation(s)
- Clare F Megarity
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - James R E Gill
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - M Clare Caraher
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK; Manchester Pharmacy School, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
| | - Ian J Stratford
- Manchester Pharmacy School, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
| | - Karen A Nolan
- Manchester Pharmacy School, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
| | - David J Timson
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
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14
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Design, synthesis and antiproliferative properties of some new 5-substituted-2-iminobenzimidazole derivatives. Eur J Med Chem 2013; 63:696-701. [DOI: 10.1016/j.ejmech.2013.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 03/03/2013] [Accepted: 03/05/2013] [Indexed: 11/23/2022]
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15
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Madhura V, Kulkarni MV, Badami S, Yenagi J, Tonannavar J. Effect of nitro groups on the photo physical properties of benzimidazolone: a solvatochromic study. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2011; 84:137-143. [PMID: 21968209 DOI: 10.1016/j.saa.2011.09.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 09/08/2011] [Accepted: 09/09/2011] [Indexed: 05/31/2023]
Abstract
Electronic absorption and fluorescence spectra of mono, di, and tri-nitro benzimidazolones are measured at room temperature (298 K) in nine solvents with different polarities and the observed shifts are compared with benzimidazolone. Ground and excited state electric dipole moments are determined using the solvatochromic method based on the bulk solvent properties, F(1)(ε, n) and F(2)(ε, n). A reasonable agreement is observed between the experimental and ab initio dipole moments. Change in dipole moment is also determined using the solvatochromic method based on the microscopic solvent polarity parameter, (E(T)(N)), which considers the polarization changes due to hydrogen bonding in different solvents. It has been observed that the correlation of the solvatochromic Stokes shifts with the parameter (E(T)(N)), is superior to that derived using bulk solvent polarity functions for all the benzimidazolones reported in the present study. Calculated difference between excited state and ground state dipole moments seems to be a good measure of the effect of nitro group when correlated with (E(T)(N)).
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Affiliation(s)
- V Madhura
- Department of Chemistry, Karnatak University, Pavate Nagar, Dharwad 580 003, India
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16
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Yang Z, Wang J, Li L, Ye C, Liu H. Synthesis and characteristic of 5,6-dinitro and 5,6-diaminobenzimidazolone-2. J Heterocycl Chem 2009. [DOI: 10.1002/jhet.104] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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17
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Nivinskas H, Sarlauskas J, Anusevicius Z, Toogood HS, Scrutton NS, Cenas N. Reduction of aliphatic nitroesters and N-nitramines by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase: quantitative structure-activity relationships. FEBS J 2008; 275:6192-203. [PMID: 19016851 DOI: 10.1111/j.1742-4658.2008.06744.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enterobacter cloacae PB2 NADPH:pentaerythritol tetranitrate reductase (PETNR) performs the biodegradation of explosive organic nitrate esters via their reductive denitration. In order to understand the enzyme substrate specificity, we have examined the reactions of PETNR with organic nitrates (n = 15) and their nitrogen analogues, N-nitramines (n = 4). The reactions of these compounds with PETNR were accompanied by the release of 1-2 mol of nitrite per mole of compound, but were not accompanied by their redox cycling and superoxide formation. The reduction rate constants (k(cat)/K(m)) of inositol hexanitrate, diglycerol tetranitrate, erythritol tetranitrate, mannitol hexanitrate and xylitol pentanitrate were similar to those of the established PETNR substrates, PETN and glycerol trinitrate, whereas the reactivities of hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine were three orders of magnitude lower. The log k(cat)/K(m) value of the compounds increased with a decrease in the enthalpy of formation of the hydride adducts [DeltaH(f)(R-O-N(OH)O(-)) or DeltaH(f)(R(1),R(2) > N-N(OH)O(-))], and with an increase in their lipophilicity (octanol/water partition coefficient, log P(ow)), and did not depend on their van der Waals' volumes. Hydrophobic organic nitroesters and hydrophilic N-nitramines compete for the same binding site in the reduced enzyme form. The role of the hydrophobic interaction of PETNR with glycerol trinitrate was supported by the positive dependence of glycerol trinitrate reactivity on the solution ionic strength. The discrimination of nitroesters and N-nitramines according to their log P(ow) values seems to be a specific feature of the Old Yellow Enzyme family of flavoenzymes.
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18
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Karatas F, Servi S, Kara H, Kiran TR, Saydam S. Investigation of oxidative status of the 2-furan-2-yl-1H-benzimidazole in rats. Biol Trace Elem Res 2008; 126:214-21. [PMID: 18781285 DOI: 10.1007/s12011-008-8202-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 07/17/2008] [Indexed: 12/25/2022]
Abstract
We investigated the influence of 2-furan-2-yl-1H-benzimidazole regarding vitamins A, E, C, selenium (Se), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) levels on rats. 2-Furan-2-yl-1H-benzimidazole was given to rats by subcutaneous injection every other day for a total of 22 injections. At the end of the experiment, Se levels were determined by using a fluorimetric method. Serum levels of vitamins A, E, C, and malondialdehyde (MDA) were determined by high-performance liquid chromatography. Glutathione peroxidase (GSH-Px) levels of erythrocytes were spectrophotometrically determined. Our experimental results showed that vitamins A, E, C, and Se levels were found generally lower than the control groups, while serum MDA level and GSH-Px activity flexibly increased, which is dependent on injection days. The observed decreases in vitamins A, E, C, and Se levels in the blood might be causally related to the increased amount of free radicals that are generated with 2-furan-2-yl-1H-benzimidazole injection. However, further investigations are needed to clarify the significance of this observation in respect with the 2-furan-2-yl-1H-benzimidazole injection.
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Affiliation(s)
- Fikret Karatas
- Department of Chemistry, Faculty of Arts and Sciences, University of Firat, 23119 Elazig, Turkey.
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19
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Zayas B, Beyley J, Terron M, Cordero M, Hernandez W, Alegría AE, Cox O. Comparison of the nucleic acid covalent binding capacity of two nitro-substituted benzazolo[3,2-a]quinolinium salts upon enzymatic reduction. Toxicol In Vitro 2007; 21:1155-64. [PMID: 17466486 PMCID: PMC2001286 DOI: 10.1016/j.tiv.2007.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Revised: 02/16/2007] [Accepted: 03/03/2007] [Indexed: 11/16/2022]
Abstract
The DNA binding capacity of two nitro-substituted benzazolo[3,2-a]quinolinium chlorides (NBQs), NBQ-38 and NBQ-95, was evaluated upon their enzymatic reduction with hypoxanthine (HX)/xanthine oxidase (XO) under anaerobic conditions. In the presence of 2'-deoxyguanosine (2'-dG) or calf thymus DNA, covalent-addition products were monitored. Reactions of each NBQ with 2'-dG or DNA differed in the NBQ to HX molar ratio. Control reactions, one without HX/OX and another under aerobic conditions, were also analyzed. Adducts were isolated and characterized by high performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS). Authentic samples of the reduced forms of these NBQs, identified as ABQ-38 and ABQ-95, were synthesized as standards to monitor bioreduction processes. HPLC analysis showed that the yield of formation of an unknown product (possibly, 2'-dG-NHBQ-38 adduct) from the reaction of NBQ-38 with 2'-dG and DNA was proportional to the HX to NBQ-38 molar ratio. ESI-MS analysis of the DNA hydrolysates showed evidence of an adduct formed upon bioreduction of NBQ-38 by the ions detection at m/z 528.3 and 454.8, consistent with chemical structures of a 2'-dG-NHBQ-38 adduct and a fragment ion. DNA adducts were not observed with NBQ-95, although the corresponding bioreduction product ABQ-95 was detected by ESI-MS. This study provides mechanistic information of these bioreductively-activated pro-drugs with potential therapeutic applications.
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Affiliation(s)
- Beatriz Zayas
- School of Environmental Affairs, Universidad Metropolitana, San Juan, Puerto Rico.
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20
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Xu J, Yang Q, Qian X, Samuelsson J, Janson JC. Assessment of 4-nitro-1,8-naphthalic anhydride reductase activity in homogenates of bakers’ yeast by reversed-phase high-performance liquid chromatography. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 847:82-7. [PMID: 17070119 DOI: 10.1016/j.jchromb.2006.09.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 09/08/2006] [Accepted: 09/15/2006] [Indexed: 10/24/2022]
Abstract
A simple reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed for the simultaneous determination of yield and conversion ratio of 4-nitro-1,8-naphthalic anhydride to 4-amino-1,8-naphthalic anhydride following incubation with a crude bakers' yeast homogenate. The analytes were separated on a C18 column in gradient mode. The detection limit of 4-amino-1,8-naphthalic anhydride is 10ng/microl when using a 10microl sample injection volume. The nitroreductase activity in the homogenate system can be assessed during the bioconversion process. The method can be used for the simultaneous detection of 4-hydroxylamino-1,8-naphthalic anhydride, an intermediate with limited stability.
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Affiliation(s)
- Jianqiang Xu
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian 116024, China
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21
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Alegria AE, Flores W, Cordones E, Rivera L, Sanchez-Cruz P, Cordero M, Cox O. Reductive activation and thiol reactivity of benzazolo[3,2-a]quinolinium salts. Toxicology 2004; 199:87-96. [PMID: 15147783 DOI: 10.1016/j.tox.2003.11.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 11/24/2003] [Accepted: 11/25/2003] [Indexed: 11/15/2022]
Abstract
Derivatives of benzazolo[3,2-a]quinolium salts (QSDs) are reductively activated by the enzymatic reducing agents hypoxanthine (or xanthine)/xanthine oxidase and NADH dehydrogenase as evidenced by the increase in rates of ferricytochrome c (Cyt(III)c) reduction and oxygen consumption, respectively. No correlation between Michaelis-Menten parameters and QSDs redox potentials was found regarding anaerobic or aerobic Cyt(III)c reduction, although maximum rates were observed for nitro-containing QSDs. However, oxygen consumption rates correlate with QSDs redox potentials when NADH dehydrogenase is used as reducing agent. QSDs bind covalently to bovine serum albumin (BSA) under anaerobic conditions, in the presence, and less in the absence, of HX/XO and only if the nitro group is present at the QSD. QSDs react with glutathione (GSH) in the presence of HX/XO but not in its absence, under anaerobic conditions. The amount of reacted GSH increases, and the relative amount of GSSG formed decreases, with an increase in the QSD reduction potential, thus indicating that GSH reacts with reduced nitro-containing QSDs mainly in a manner which does not involve the production of GSSG, presumably, through the formation of the nitroso-QSD-GSH conjugate. QSDs are, thus, novel nitro-containing heterocyclic compounds which could be bioreductively activated to react with oxygen and thiols.
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Affiliation(s)
- Antonio E Alegria
- Department of Chemistry, University of Puerto Rico at Humacao, Humacao, PR 00791, USA.
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22
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Sarlauskas J, Nemeikaite-Ceniene A, Anusevicius Z, Miseviciene L, Julvez MM, Medina M, Gomez-Moreno C, Cenas N. Flavoenzyme-catalyzed redox cycling of hydroxylamino- and amino metabolites of 2,4,6-trinitrotoluene: implications for their cytotoxicity. Arch Biochem Biophys 2004; 425:184-92. [PMID: 15111126 DOI: 10.1016/j.abb.2004.02.043] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Revised: 02/19/2004] [Indexed: 11/24/2022]
Abstract
The toxicity of 2,4,6-trinitrotoluene (TNT), a widespread environmental contaminant, is exerted through its enzymatic redox cycling and/or covalent binding of its reduction products to proteins and DNA. In this study, we examined the possibility of another cytotoxicity mechanism of the amino- and hydroxylamino metabolites of TNT, their flavoenzyme-catalyzed redox cycling. The above compounds acted as redox-cycling substrates for single-electron transferring NADPH:cytochrome P-450 reductase (P-450R) and ferredoxin:NADP(+) reductase (FNR), as well as substrates for the two-electron transferring flavoenzymes rat liver NAD(P)H:quinone oxidoreductase (NQO1) and Enterobacter cloacae NAD(P)H:nitroreductase (NR). Their reactivity in P-450R-, FNR-, and NR-catalyzed reactions increased with an increase in their single-electron reduction potential (E(1)(7)) or the decrease in the enthalpy of free radical formation. The cytotoxicity of the amino- and hydroxylamino metabolites of TNT towards bovine leukemia virus-transformed lamb kidney fibroblasts (line FLK) was partly prevented by the antioxidant N,N'-diphenyl-p-phenylene diamine and desferrioxamine, and potentiated by 1,3-bis-(2-chloroethyl)-1-nitrosourea, thus pointing to the involvement of oxidative stress. In general, their cytotoxicity increased with an increase in their electron accepting properties, or their reactivity towards the single-electron transferring FNR and P-450R. Thus, our data imply that the flavoenzyme-catalyzed redox cycling of amino and hydroxylamino metabolites of TNT may be an important factor in their cytotoxicity.
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Affiliation(s)
- Jonas Sarlauskas
- Institute of Biochemistry, Sector of Xenobiotics Biochemistry, MokslininkuSt. 12, Vilnius 2600, Lithuania
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23
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Osman AM, Boeren S. Studies on the DT-diaphorase-catalysed reaction employing quinones as substrates: evidence for a covalent modification of DT-diaphorase by tetrachloro-p-benzoquinone. Chem Biol Interact 2004; 147:99-108. [PMID: 14726156 DOI: 10.1016/j.cbi.2003.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In this study, the kinetic parameters, V(max) and K(m), of rat liver DT-diaphorase were determined for a series of p-benzoquinones, with methyl, methoxy, cyano, hydroxy and halo substituents. The results show that there is no correlation between the experimentally determined rates of p-benzoquinone reduction by DT-diaphorase and the calculated chemical reactivity of the examined substrates as expressed by the energy of the lowest unoccupied molecular orbital, E(LUMO). However, a reasonable correlation was found between the natural logarithm of V(max)/K(m) and the partition coefficient of the p-benzoquinones (r=0.81). Furthermore, tetrachloro-p-benzoquinone, one of the tested quinones is shown to be an inhibitor of rat DT-diaphorase. The presence of bovine serum albumin (BSA) in the incubation mixture protects DT-diaphorase against the inactivation by tetrachloro-p-benzoquinone, probably by interacting with the quinone. Maldi-Tof analysis of the incubation mixture of the purified DT-diaphorase and tetrachloro-p-benzoquinone showed that every subunit of the enzyme shifted about +414 amu, whereas the dimer shifted about +849 amu relative to control values. This indicates a covalent modification of the rat liver DT-diaphorase by tetrachloro-p-benzoquinone.
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Affiliation(s)
- Ahmed M Osman
- Institute for Inland Water Management and Waste-water Treatment, P.O. Box 17, 8200 AA Lelystad, The Netherlands.
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24
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Sánchez-Moreno MJ, Gómez-Coca RB, Fernández-Botello A, Ochocki J, Kotynski A, Griesser R, Sigel H. Synthesis and acid-base properties of (1H-benzimidazol-2-yl-methyl)phosphonate (Bimp2-). Evidence for intramolecular hydrogen-bond formation in aqueous solution between (N-1)H and the phosphonate group. Org Biomol Chem 2003; 1:1819-26. [PMID: 12926375 DOI: 10.1039/b301281f] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis of (1H-benzimidazol-2-yl-methyl)phosphonic acid, H2(Bimp)+/-, is described: 2-chloromethylbenzimidazole was reacted with ethylchloroformate to give 1-carboethoxy-2-chloromethylbenzimidazole which was treated with trimethyl phosphite and after hydrolysis with aqueous HBr H2(Bimp)+/- was obtained. In H2(Bimp)+/- one proton is at the N-3 site and the other at the phosphonate group; both acidity constants were determined in aqueous solution by potentiometric pH titrations (25 degrees C; I = 0.1 M, NaNO3) and this furnished the pKa values of 5.37 +/- 0.02 and 7.41 +/- 0.02, respectively. The acidity constant for the release of the primary proton from the P(O)(OH)2 group of H3(Bimp)+ was estimated: pKa = 1.5 +/- 0.2. Moreover, Bimp2- can be further deprotonated at its neutral (N-1/N-3)H site to give the benzimidazolate residue, but this reaction occurs only in strongly alkaline solution (KOH); application of the H_ scale developed by G. Yagil (J. Phys. Chem., 1967, 71, 1034) together with UV spectrophotometric measurements gave pKa = 14.65 +/- 0.12. Comparisons with acidity constants taken from the literature show that this latter pKa value is far too large and this allows the conclusion that an intramolecular hydrogen bond is formed between the (N-1/N-3)H site and the phosphonate group of Bimp2-; the formation degree of this hydrogen-bonded isomer is estimated to be 98 +/- 2%. The general relevance of this and the other results are shortly discussed and the species distribution for the Bimp system in dependence on pH is provided.
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Affiliation(s)
- María José Sánchez-Moreno
- Department of Inorganic Chemistry, Faculty of Pharmacy, University of Granada, Campus de Cartuja, s/n, E-18071 Granada, Spain
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Kapinya KJ, Harms U, Harms C, Blei K, Katchanov J, Dirnagl U, Hörtnagl H. Role of NAD(P)H:quinone oxidoreductase in the progression of neuronal cell death in vitro and following cerebral ischaemia in vivo. J Neurochem 2003; 84:1028-39. [PMID: 12603827 DOI: 10.1046/j.1471-4159.2003.01601.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A direct involvement of the antioxidant enzyme NAD(P)H:quinone oxidoreductase (NQO1) in neuroprotection has not yet been shown. The aim of this study was to examine changes, localization and role of NQO1 after different neuronal injury paradigms. In primary cultures of rat cortex the activity of NQO1 was measured after treatment with ethylcholine aziridinium (AF64A; 40 micro m), inducing mainly apoptotic cell death, or oxygen-glucose deprivation (OGD; 120 min), which combines features of apoptotic and necrotic cell death. After treatment with AF64A a significant NQO1 activation started after 24 h. Sixty minutes after OGD a significant early induction of the enzyme was observed, followed by a second increase 24 h later. Enzyme activity was preferentially localized in glial cells in control and injured cultures, however, expression also occurred in injured neuronal cells. Inhibition of the NQO1 activity by dicoumarol, cibacron blue or chrysin (1-100 nM) protected the cells both after exposure to AF64A or OGD as assessed by the decreased release of lactate dehydrogenase. Comparable results were obtained in vivo using a mouse model of focal cerebral ischaemia. Dicoumarol treatment (30 nmol intracerebroventricular) reduced the infarct volume by 29% (p = 0.005) 48 h after the insult. After chemical induction of NQO1 activity by t-butylhydroquinone in vitro neuronal damage was exaggerated. Our data suggest that the activity of NQO1 is a deteriorating rather than a protective factor in neuronal cell death.
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Affiliation(s)
- Krisztian J Kapinya
- Department of Experimental Neurology, Medical Faculty Charité, Humboldt-University Berlin, Dorotheenstrasse 94, D-10098 Berlin, Germany
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Anusevicius Z, Sarlauskas J, Cenas N. Two-electron reduction of quinones by rat liver NAD(P)H:quinone oxidoreductase: quantitative structure-activity relationships. Arch Biochem Biophys 2002; 404:254-62. [PMID: 12147263 DOI: 10.1016/s0003-9861(02)00273-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Mammalian NAD(P)H:quinone oxidoreductase (NQO1, DT-diaphorase, EC 1.6.99.2) catalyzes the two-electron reduction of quinones and plays one of the main roles in the bioactivation of quinoidal drugs. In order to understand the enzyme substrate specificity, we have examined the reactions of rat NQO1 with a number of quinones with available potentials of single-electron (E(1)(7)) reduction and pK(a) of their semiquinones. The hydride transfer potentials (E(7)(H(-))) were calculated from the midpoint potentials of quinones and pK(a) of hydroquinones. Our findings imply that benzo- and naphthoquinones with a van der Waals volume (VdWvol) < or = 200 A(3) are much more reactive than glutathionyl-substituted naphthoquinones, polycyclic quinones, and FMN (VdWvol>200 A(3)) with the same reduction potentials. The entropies of activation (DeltaS(not equal)) in the reduction of "fast" oxidants are equal to -84 to -76 J mol(-1) K(-1), whereas in the reduction of "slow" oxidants Delta S(not equal)=-36 to -11 J mol(-1) K(-1). The large negative Delta S(not equal) in the reduction of fast oxidants may be explained by their better electronic coupling with reduced FAD or the formation of charge-transfer complexes, since fast oxidants bind at the dicumarol binding site, whereas the binding of some slow oxidants outside it has been demonstrated. The reactivity of quinones may be equally well described in terms of the three-step (e(-),H(+),e(-)) hydride transfer, using E(1)(7), pK(a)(QH*), and VdWvol as correlation parameters, or in terms of single-step (H(-)) hydride transfer, using E(7)(H(-)) and VdWvol in the correlation. The analysis of NQO1 reactions with single-electron acceptors and quinones using an "outer-sphere" electron transfer model points to the possibility of a three-step hydride transfer.
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27
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Cenas N, Nemeikaite-Ceniene A, Sergediene E, Nivinskas H, Anusevicius Z, Sarlauskas J. Quantitative structure-activity relationships in enzymatic single-electron reduction of nitroaromatic explosives: implications for their cytotoxicity. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1528:31-8. [PMID: 11514095 DOI: 10.1016/s0304-4165(01)00169-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanisms of cytotoxicity of polynitroaromatic explosives, an important group of environmental pollutants, remain insufficiently studied so far. We have found that the rate constants of single-electron enzymatic reduction, and the enthalpies of single-electron reduction of nitroaromatic compounds (DeltaHf(ArNO(2)(-*)), obtained by quantum mechanical calculation, may serve as useful tools for the analysis of cytotoxicity of nitroaromatic explosives with respect to the possible involvement of oxidative stress. The single-electron reduction rate constants of a number of explosives including 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenyl-N-methylnitramine (tetryl), and model nitroaromatic compounds by ferredoxin:NADP(+) reductase (FNR, EC 1.18.1.2) and NADPH:cytochrome P-450 reductase (P-450R, EC 1.6.2.4) increased with a decrease in DeltaHf(ArNO(2)(-*)). This indicates that the reduction rates are determined by the electron transfer energetics, but not by the particular structure of the explosives. The cytotoxicity of explosives to bovine leukemia virus-transformed lamb kidney fibroblasts (line FLK) increased with a corresponding increase in their reduction rate constant by P-450R and FNR, or with a decrease in their DeltaHf(ArNO(2)(-*)). This points to an importance of oxidative stress in the toxicity of explosives in this cell line, which was further evidenced by the protective effects of desferrioxamine and the antioxidant N,N'-diphenyl-p-phenylene diamine, and an increase in lipid peroxidation. DT-diaphorase (EC 1.6.99.2) exerted a minor and equivocal role in the cytotoxicity of explosives to FLK cells.
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Affiliation(s)
- N Cenas
- Institute of Biochemistry, Vilnius, Lithuania.
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28
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Nivinskas H, Koder RL, Anusevicius Z, Sarlauskas J, Miller AF, Cenas N. Quantitative structure-activity relationships in two-electron reduction of nitroaromatic compounds by Enterobacter cloacae NAD(P)H:nitroreductase. Arch Biochem Biophys 2001; 385:170-8. [PMID: 11361014 DOI: 10.1006/abbi.2000.2127] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Enterobacter cloacae NAD(P)H:nitroreductase (NR; EC 1.6.99.7) catalyzes the reduction of a series of nitroaromatic compounds with steady-state bimolecular rate constants (kcat/Km) ranging from 10(4) to 10(7) M(-1) s(-1). In agreement with a previously proposed scheme of two-step four-electron reduction of nitroaromatics by NR (Koder, R. L., and Miller, A.-F. (1998) Biochim. Biophys. Acta 1387, 395-405), 2 mol NADH per mole mononitrocompound were oxidized. An oxidation of excess NADH by polinitrobenzenes, including explosives 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenyl-N-methylnitramine (tetryl), has been observed as a slower secondary process, accompanied by O2 consumption. This type of "redox cycling" was not related to reactions of nitroaromatic anion-radicals, but was caused by the autoxidation of relatively stable reaction products. The initial reduction of tetryl and other polinitrophenyl-N-nitramines by E. cloacae NR was analogous to a two-step four-electron reduction mechanism of TNT and other nitroaromatics. The logs kcat/Km of all the compounds examined exhibited parabolic dependence on their enthalpies of single-electron or two-electron (hydride) reduction, obtained by quantum mechanical calculations. This type of quantitative structure-activity relationship shows that the reactivity of nitroaromatics towards E. cloacae nitroreductase depends mainly on their hydride accepting properties, but not on their particular structure, and does not exclude the possibility of multistep hydride transfer.
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Affiliation(s)
- H Nivinskas
- Institute of Biochemistry, Vilnius, Lithuania
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Gutierrez PL. The role of NAD(P)H oxidoreductase (DT-Diaphorase) in the bioactivation of quinone-containing antitumor agents: a review. Free Radic Biol Med 2000; 29:263-75. [PMID: 11035255 DOI: 10.1016/s0891-5849(00)00314-2] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Bioactivation of quinone-containing anticancer agents has been studied extensively within the context of the chemistry and structure of the individual quinones which may result in various mechanisms of bioactivation and activity. In this review we focus on the two electron enzymatic reduction/activation of quinone-containing anticancer agents by DT Diaphorase (DTD). This enzyme has become important in oncopharmacology because its activity varies with tissues and it has been found to be elevated in tumors. Thus, a selective tumor cell kill can exist for agents that are good substrates for this enzyme. In addition, the enzyme can be induced by a variety of agents, a fact that can be used in chemotherapy. That is induction by a nontoxic agent followed by treatment with a good DT-Diaphorase substrate. A wide variety of anticancer drugs are discussed some of which are not good substrates such as Adriamycin, and some of which are excellent substrates. The latter category includes a variety of quinone containing alkylating agents.
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Affiliation(s)
- P L Gutierrez
- The University of Maryland Greenebaum Cancer Center, University of Maryland Medical School, Baltimore, 21201, USA.
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Sergediene E, Jönsson K, Szymusiak H, Tyrakowska B, Rietjens IM, Cenas N. Prooxidant toxicity of polyphenolic antioxidants to HL-60 cells: description of quantitative structure-activity relationships. FEBS Lett 1999; 462:392-6. [PMID: 10622732 DOI: 10.1016/s0014-5793(99)01561-6] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Polyphenolic antioxidants exhibited a dose-dependent toxicity against human promyelocytic leukemia cells (HL-60). Their action was accompanied by malondialdehyde formation, and was partly prevented by desferrioxamine and the antioxidant N,N'-diphenyl-p-phenylene diamine. This points to a prooxidant character of their cytotoxicity. A quantitative structure-activity relationship (QSAR) has been obtained to describe the cytotoxicity of 13 polyphenolic antioxidants belonging to three different groups (flavonoids, derivatives of gallic and caffeic acid): log cL50 (microM) = (2.7829+/-0.2339)+(1.2734+/-0.4715) Ep/2 (V)-(0.3438+/-0.0582) log P (r2 = 0.8129), where cL50 represents the concentration for 50% cell survival, Ep/2 represents the voltammetric midpoint potential, and P represents the octanol/water partition coefficient. Analogous QSARs were obtained using enthalpies of single-electron oxidation of these compounds, obtained by quantum-mechanical calculations. These findings clearly point to two important characteristics determining polyphenol cytotoxicity, namely their ease of oxidation and their lipophilicity.
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Affiliation(s)
- E Sergediene
- Institute of Biochemistry, Mokslininku, Lithuania
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Kapinos LE, Sigel H. On the Metal-Ion-Coordinating Properties of the Benzimidazolate Residue in Aqueous Solution – Extent of Acidification of Benzimidazole-(N3)H Sites by (N1)-Coordinated Divalent Metal Ions. Eur J Inorg Chem 1999. [DOI: 10.1002/(sici)1099-0682(199910)1999:10<1781::aid-ejic1781>3.0.co;2-h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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32
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Anusevicius Z, Soffers AE, Cenas N, Sarlauskas J, Martinez-Julvez M, Rietjens IM. Quantitative structure activity relationships for the electron transfer reactions of Anabaena PCC 7119 ferredoxin-NADP+ oxidoreductase with nitrobenzene and nitrobenzimidazolone derivatives: mechanistic implications. FEBS Lett 1999; 450:44-8. [PMID: 10350054 DOI: 10.1016/s0014-5793(99)00464-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The steady state single electron reduction of polynitroaromatics by ferredoxin-NADP+ oxidoreductase (EC 1.18.1.2) from cyanobacterium Anabaena PCC 7119 has been studied and quantitative structure activity relationships are described. The solubility of the polynitroaromatics as well as their reactivity towards ferredoxin-NADP+ oxidoreductase are markedly higher than those for previously studied mononitroaromatics and this enabled the independent measurement of the kinetic parameters-k(cat) and Km. Interestingly, the natural logarithm of the bimolecular rate constant, k(cat)/Km, and also the natural logarithm of k(cat) correlate with the calculated energy of the lowest unoccupied molecular orbital of the polynitroaromatic substrates. The minimal kinetic model in line with these quantitative structure activity relationships is a ping-pong mechanism which includes substrate binding equilibria in the second half reaction.
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Affiliation(s)
- Z Anusevicius
- Laboratory of Biochemistry, Wageningen Agricultural University, The Netherlands
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Anusevicius Z, Sarlauskas J, Nivinskas H, Segura-Aguilar J, Cenas N. DT-diaphorase catalyzes N-denitration and redox cycling of tetryl. FEBS Lett 1998; 436:144-8. [PMID: 9781667 DOI: 10.1016/s0014-5793(98)01115-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Rat liver DT-diaphorase (EC 1.6.99.2) catalyzed reductive N-denitration of tetryl (2,4,6-tri-nitrophenyl-N-methylnitramine) and 2,4-dinitrophenyl-N-methylnitramine, oxidizing the excess of NADPH. The reactions were accompanied by oxygen consumption and superoxide dismutase-sensitive reduction of added cytochrome c and reductive release of Fe2+ from ferritin. Quantitatively, the reactions of DT-diaphorase proceeded like single-electron reductive N-denitration of tetryl by ferredoxin:NADP+ reductase (EC 1.18.1.2) (Shah, M.M. and Spain, J.C. (1996) Biochem. Biophys. Res. Commun. 220, 563-568), which was additionally checked up in this work. Thus, although reductive N-denitration of nitrophenyl-N-nitramines is a net two-electron (hydride) transfer process, DT-diaphorase catalyzed the reaction in a single-electron way. These data point out the possibility of single-electron transfer steps during obligatory two-electron (hydride) reduction of quinones and nitroaromatics by DT-diaphorase.
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Anusevicius Z, Soffers AE, Cénas N, Sarlauskas J, Segura-Aguilar J, Rietjens IM. Quantitative structure activity relationships for the conversion of nitrobenzimidazolones and nitrobenzimidazoles by DT-diaphorase: implications for the kinetic mechanism. FEBS Lett 1998; 427:325-9. [PMID: 9637250 DOI: 10.1016/s0014-5793(98)00456-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Quantitative structure activity relationships (QSARs) for the conversion of nitrobenzimidazolones and nitrobenzimidazoles by rat liver DT-diaphorase (EC 1.6.99.2) are described. The parameter used for description of the QSARs is the energy of the lowest unoccupied molecular orbital (E(LUMO)) of the nitroaromatic compounds. Interestingly, correlations with E(LUMO) were observed for both the natural logarithm of kcat, but also for the natural logarithm of kcat/Km. The minimal kinetic model in line with these QSARs is a ping-pong mechanism that includes a substrate binding equilibrium in the second half reaction.
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Affiliation(s)
- Z Anusevicius
- Department of Biomolecular Sciences, Laboratory of Biochemistry, Agricultural University, The Netherlands
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