A Review of NAD(P)H:Quinone Oxidoreductase 1 (NQO1); A Multifunctional Antioxidant Enzyme (original) (raw)
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NQO1 Enzyme and its Role in Cellular Protection; an Insight
Iberoamerican Journal of Medicine, 2020
NAD(P)H:quinone oxidoreductase 1 (NQO1) is considered as one of the most significant enzyme in cellular defense due to its ability to detoxify reactive quinones and quinone imines to their less toxic hydroquinones forms. NQO1 is a xenobiotic metabolizing cytosolic enzyme that catalyzes the reduction of two- or four-electron of numerous exogenous and endogenous quinones by utilizing flavin adenine dinucleotide (FAD) as a cofactor. NQO1 enzyme exists as a homodimer enzyme and is biochemically identified by its noticeable ability to utilize either NADH or NADPH as reducing cofactors and by its inhibition by anticoagulant agents such as dicumarol. NQO1 is a distinctly inducible enzyme and known to be controlled by the Nrf2-Keap1 pathway. The importance of the antioxidant activities exhibited by NQO1 enzyme in suppressing the oxidative stress status is provided by demonstration that induction or reduction of NQO1 levels are linked with increased and reduced susceptibilities to oxidative ...
Archives of Biochemistry and Biophysics, 2010
NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1) is a widely-distributed FAD-dependent flavoprotein that promotes obligatory 2-electron reductions of quinones, quinoneimines, nitroaromatics, and azo dyes, at rates that are comparable with NADH or NADPH. These reductions depress quinone levels and thereby minimize opportunities for generation of reactive oxygen intermediates by redox cycling, and for depletion of intracellular thiol pools. NQO1 is a highlyinducible enzyme that is regulated by the Keap1/Nrf2/ARE pathway. Evidence for the importance of the antioxidant functions of NQO1 in combating oxidative stress is provided by demonstrations that induction of NQO1 levels or their depletion (knockout, or knockdown) are associated with decreased and increased susceptibilities to oxidative stress, respectively. Furthermore, benzene genotoxicity is markedly enhanced when NQO1 activity is compromised. Not surprisingly, human polymorphisms that suppress NQO1 activities are associated with increased predisposition to disease. Recent studies have uncovered protective roles for NQO1 that apparently are unrelated to its enzymatic activities. NQO1 binds to and thereby stabilizes the important tumor suppressor p53 against proteasomal degradation. Indeed, NQO1 appears to regulate the degradative fate of other proteins. These findings suggest that NQO1 may exercise a selective "gatekeeping" role in regulating the proteasomal degradation of specific proteins, thereby broadening the cytoprotective role of NQO1 far beyond its highly effective antioxidant functions.
Chemico-Biological Interactions, 2000
NAD(P)H:quinone oxidoreductase 1 (NQO1) is an obligate two-electron reductase that is involved in chemoprotection and can also bioactivate certain antitumor quinones. This review focuses on detoxification reactions catalyzed by NQO1 and its role in antioxidant defense via the generation of antioxidant forms of ubiquinone and vitamin E. Bioactivation reactions catalyzed by NQO1 are also summarized and the development of new antitumor agents for the therapy of solid tumors with marked NQO1 content is reviewed. NQO1 gene regulation and the role of the antioxidant response element and the xenobiotic response element in transcriptional regulation is summarized. An overview of genetic polymorphisms in NQO1 is presented and biological significance for chemoprotection, cancer susceptibility and antitumor drug action is discussed. : S 0 0 0 9 -2 7 9 7 ( 0 0 ) 0 0 1 9 9 -X
PloS one, 2018
NQO1 is a FAD containing NAD(P)H-dependent oxidoreductase that catalyzes the reduction of quinones and related substrates. In cells, NQO1 participates in a number of binding interactions with other proteins and mRNA and these interactions may be influenced by the concentrations of reduced pyridine nucleotides. NAD(P)H can protect NQO1 from proteolytic digestion suggesting that binding of reduced pyridine nucleotides results in a change in NQO1 structure. We have used purified NQO1 to demonstrate the addition of NAD(P)H induces a change in the structure of NQO1; this results in the loss of immunoreactivity to antibodies that bind to the C-terminal domain and to helix 7 of the catalytic core domain. Under normal cellular conditions NQO1 is not immunoprecipitated by these antibodies, however, following treatment with β-lapachone which caused rapid oxidation of NAD(P)H NQO1 could be readily pulled-down. Similarly, immunostaining for NQO1 was significantly increased in cells following tr...
ATP independent proteasomal degradation of NQO1 in BL cell lines
Biochimie, 2012
Human NAD(P)H: quinone oxidoreductase 1 (NQO1) catalyzes the obligatory two-electron reduction of quinones. For this peculiar catalytic mechanism, the enzyme is considered an important cytoprotector. The NQO1 gene is expressed in all human tissues, unless a polymorphism due to C609T point mutation is present. This polymorphism produces a null phenotype in the homozygous condition and reduced enzyme activity in the heterozygous one. We previously demonstrated that two cell lines of haematopoietic origin, HL60 and Raji cells, possess the same heterozygous genotype, but different phenotypes; as expected for a heterozygous condition the HL60 cell line showed a low level of enzyme activity, while the Raji cell line appeared as null phenotype. The level of NQO1 mRNA was similar in the two cell lines and the different phenotype was not due to additional mutations or to expression of alternative splicing products. Here we show that in Raji BL cell line with heterozygous genotype the null NQO1 phenotype is due to 20S proteasome degradation of wild type and mutant protein isoforms and is not directly linked to C609T polymorphism. This finding may have important implications in B-cell differentiation, in leukaemia risk evaluation and in chemotherapy based on proteasome inhibitors.
Antioxidants
Human NAD(P)H:quinone oxidoreductase 1 (hNQO1) is a multifunctional and antioxidant stress protein whose expression is controlled by the Nrf2 signaling pathway. hNQO1 dysregulation is associated with cancer and neurological disorders. Recent works have shown that its activity is also modulated by different post-translational modifications (PTMs), such as phosphorylation, acetylation and ubiquitination, and these may synergize with naturally-occurring and inactivating polymorphisms and mutations. Herein, I describe recent advances in the study of the effect of PTMs and genetic variations on the structure and function of hNQO1 and their relationship with disease development in different genetic backgrounds, as well as the physiological roles of these modifications. I pay particular attention to the long-range allosteric effects exerted by PTMs and natural variation on the multiple functions of hNQO1.
Molecular pharmacology, 2001
The NAD(P)H:quinone oxidoreductase 1 (NQO1)*2 polymorphism is characterized by a single proline-to-serine amino acid substitution. Cell lines and tissues from organisms genotyped as homozygous for the NQO1*2 polymorphism are deficient in NQO1 activity. In studies with cells homozygous for the wild-type allele and cells homozygous for the mutant NQO1*2 allele, no difference in the half-life of NQO1 mRNA transcripts was observed. Similarly, in vitro transcription/translation studies showed that both wild-type and mutant NQO1 coding regions were transcribed and translated into full-length protein with equal efficiency. Protein turnover studies in NQO1 wild-type and mutant cell lines demonstrated that the half-life of wild-type NQO1 was greater than 18 h, whereas the half-life of mutant NQO1 was 1.2 h. Incubation of NQO1 mutant cell lines with proteasome inhibitors increased the amount of immunoreactive NQO1 protein, suggesting that mutant protein may be degraded via the proteasome path...
FEBS Letters, 2014
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.
Biochemistry, 2011
T here are two quinone reductases that occur in mammalian systems, NAD(P)H:quinone oxidoreductase 1 (NQO1, EC 1.6.99.2) and NRH:quinone oxidoreductase 2 (NQO2, EC 1.10.99.2). NQO1 was originally characterized by Ernster and Navazio 1,2 and was probably identical to an enzyme isolated by Martius a few years earlier. Interestingly, NQO2 was cloned and fully characterized by Jaiswal et al. 5 but as highlighted by Zhao et al. 6 was also found to be identical to a flavoprotein isolated 30 years earlier. 7 Both NQO1 and NQO2 are homodimeric flavoproteins, containing one FAD site per monomer, that utilize pyridine nucleotide cofactors to catalyze the direct two-electron reduction of a broad range of quinone substrates. However, NQO2 differs from NQO1 in that it utilizes dihydronicotinamide riboside (NRH) instead of NAD(P)H as the cofactor. In addition, in comparison to NQO1, which is usually strongly expressed in solid tumors, 10 higher levels of NQO2 expression are found in red blood cells 11 and in leukemias. With respect to quinone substrates, NQO2 has been suggested to preferentially reduce o-quinones derived from catecholamines and estrogen, which has led to its proposed involvement in neurodegenerative diseases and breast cancer. 13,14 NQO2 has been shown to reduce numerous antitumor quinones in vitro, including mitomycin C, 15 RH1, 16 and the HSP90 inhibitor 17AAG, 17 while the antitumor activity of CB1954, a non-quinone dinitrobenzamide-containing compound currently in clinical trials, relies on targeted activation by NQO2 via nitroreduction. The identification of inhibitors for NQO2 has generated considerable interest. Despite structural similarities between NQO2 and NQO1, commonly used NQO1 inhibitors such as dicoumarol 19 and ES936 20 are extremely poor inhibitors of NQO2, while conversely, inhibitors of NQO2 such as resveratrol and quercetin have been shown to selectively inhibit NQO2 but not NQO1. 21À23 Previous studies have shown that resveratrol, 21,22 quercetin, 23 chloroquine, 11,24 and melatonin 9,25 can inhibit the catalytic activity of NQO2 but do so reversibly. In addition to inhibiting NQO2, these compounds have also been ABSTRACT: We describe a series of indolequinones as efficient mechanism-based inhibitors of NRH:quinone oxidoreductase 2 (NQO2) for use either in cellular or cell-free systems. Compounds were designed to be reduced in the active site of the enzyme leading to loss of a substituted phenol leaving group and generation of a reactive iminium electrophile. Inhibition of NQO2 activity was assessed in both cell-free systems and the human leukemia K562 cell line. Inhibition of recombinant human NQO2 by the indolequinones was NRH-dependent, with kinetic parameters characteristic of mechanism-based inhibition and partition ratios as low as 2.0. Indolequinones inhibited NQO2 activity in K562 cells at nanomolar concentrations that did not inhibit NQO1 and were nontoxic to cells. Computation-based molecular modeling simulations demonstrated favorable conformations of indolequinones positioned directly above and in parallel with the isoalloxazine ring of FAD, and mass spectrometry extended our previous finding of adduction of the FAD in the active site of NQO2 by an indolequinone-derived iminium electrophile to the wider series of indolequinone inhibitors. Modeling combined with biochemical testing identified key structural parameters for effective inhibition, including a 5-aminoalkylamino side chain. Hydrogen bonding of the terminal amine nitrogen in the aminoalkylamino side chain was found to be critical for the correct orientation of the inhibitors in the active site. These indolequinones were irreversible inhibitors and were found to be at least 1 order of magnitude more potent than any previously documented competitive inhibitors of NQO2 and represent the first mechanism-based inhibitors of NQO2 to be characterized in cellular systems.