NAD(P)H dehydrogenase [quinone] 1 is an enzyme that in humans is encoded by the NQO1 gene. [5] This protein-coding gene is a member of the NAD(P)H dehydrogenase (quinone) family and encodes a 2-electron reductase (enzyme). This FAD-binding protein forms homodimers and performs two-electron reduction of quinones to hydroquinones and of other redox dyes. It has a preference for short-chain acceptor quinones, such as ubiquinone, benzoquinone, juglone and duroquinone. [6] This gene has an important paralog NQO2. This protein is located in the cytosol. [7]
NQO1 enzyme expression can be induced by dioxin [8] and inhibited by dicoumarol. [9]
This gene is a member of the NAD(P)H dehydrogenase (quinone) family and encodes a cytoplasmic 2-electron reductase. This FAD-binding protein forms homodimers and reduces quinones to hydroquinones. This enzyme facilitates the two electron reduction of quinone to hydroquinone. NQO1-mediated two electron reduction of quinone to hydroquinone thereby indirectly prevents the one electron reduction of quinone to the semiquinone free radical. [10]
The ubiquitin-independent p53 degradation pathway is regulated by NQO1. NQO1 stabilizes p53, protecting it from degradation. Individuals with decreased NQO1 expression/activity have reduced p53 stability, which may lead to resistance to drugs such as chemotherapeutics. [11]
Quinonoid compounds generate reactive oxygen species (ROS) via redox cycling mechanisms and arylating nucleophiles. NQO1 removes quinone from biological systems through detoxification reaction: NAD(P)H + a quinone → NAD(P)+ + a hydroquinone. This reaction oxidises the substrate without the formation of damaging semiquinone and oxygen free radical species. The localization of NQO1 in epithelial and endothelial tissues of mice, rats and humans indicates their importance in detoxifying agent, since their location facilitates exposure to compounds entering the body.
The enzyme is also involved in biosynthetic processes such as the vitamin K-dependent gamma-carboxylation of glutamate residues in prothrombin synthesis. [12] NQO1 catalyzes the reduction of vitamin K1, K2 and K3 into their hydroquinone form, but it only has a high affinity for Vitamin K3. Vitamin K hydroquinone serves as a cofactor for vitamin K γ‐carboxylase that catalyzes γ‐carboxylation of specific glutamic acid residues in Gla‐factors/proteins (Gla domain) leading to their activation and participation in blood clotting and bone metabolism. Vitamin K is used as radiation sensitizer or in mixtures with other chemotherapeutic drugs to treat several types of cancer. ROS generated in redox cycling contributes to anticancer activity of vitamin K. NQO1 competes with enzymes that redox cycle vitamin K to formation of semiquinone and ROS. NQO1is therefore able to detoxify vitamin K3 and protect cells against oxidative stress. [13]
Several anti-tumor agents such as mitosenes, indolequinones, aziridinylbenzoquinones and β-lapachone have been designed be bioactivated by NQO1 from various prodrugs. The high levels of NQO1 expression in many human solid tumors compared to normal tissue ensures their selective activation within tumor cells. [14] [15]
NQO1 plays a role in ubiquinone and vitamin E quinone metabolism. These quinones protect cellular membranes from peroxidative injury in their reduced state. Furthermore, reduced forms of ubiquinone and vitamin E quinone have been shown to possess antioxidant properties that are superior to their non-reduced forms. [16]
One widespread single-nucleotide polymorphism of the NQO1 gene (NQO1*2), found homozygous in 4% to 20% of different populations, has found to be connected with different forms of cancer and a lowered efficiency of some chemotherapeutics like mitomycin C. This single nucleotide polymorphism leads to a proline serine exchange on position 187. NAD(P)H dehydrogenase [quinone] 1 P187S has been shown to have a lowered activity and stability. Crystallographic and nuclear magnetic resonance data show that the reason for this different behaviour is found in a flexible C-terminus of the protein leading to a destabilization of the whole protein. [17] Recent pharmacological research suggests feasibility of genotype-directed redox chemotherapeutic intervention targeting NQO1*2 breast cancer. [18]
A comprehensive meta-analysis showed an association between overall cancer risk and P187S. [19]
One further single nucleotide polymorphism, found homozygous in 0% to 5% of different ethnic population, is leading to an amino acid exchange on position 139 from arginine to tryptophane. [20] Furthermore, an alternative RNA splicing site is created leading to a loss of the quinone binding site. [21] The variant protein of NQO1*3 has similar stability as its wild-type counterpart. The variation between the two is substrate specific and it has reduced activity for some substrates. [22] It has been recently shown that the NQO1*3 polymorphism may also lead to reduced NQO1 protein expression. [11]
NAD(P)H dehydrogenase (quinone 1) has been shown to interact with HSPA4, [23] p53, p33 and p73. [17]
External (via chemicals) and internal (stress response or caloric restriction) induction of NQO1 is mediated solely through the Keap1/Nrf2/ARE. Keap1 acts as the sensor which loses its ability to target Nrf2 for degradation upon exposure to the inducers. Nrf2 is consequently stabilized and accumulated in the nucleus upon which it binds to the AREs and initiates expression of cytoprotective genes including NQO1. [24]
p53 and p73 are tumor suppressor proteins and their degradation is tightly regulated by ubiquitination. Recently it was shown that their degradation can also occur via an ubiquitin-independent process; [25] NQO1 blocks p53 and p73 degradation in the presence of NADH and protects them from 20S proteasomal degradation. This protein-protein interaction between p53 and NQO1 was non-catalytic. [26]
Ornithine decarboxylase (ODC), is a labile protein that is the first rate-limiting enzyme in polyamine biosynthesis. Its degradation is regulated by antizyme that is induced by polyamine production. NQO1 has been shown to stabilize the degradation of ODC by binding to it and protecting it from 20S proteasomal degradation.
Mutations in this gene have been associated with tardive dyskinesia (TD), an increased risk of hematotoxicity after exposure to benzene, and susceptibility to various forms of cancer. Altered expression of this protein has been seen in many tumors and is also associated with Alzheimer's disease (AD). [10]
Benzene poisoning can increase risk of hematological cancers and other disorders. The mechanism of benzene metabolism and how it affects toxicity has not been completely understood. A general observation is that there is high variation in the extent of damage due to benzene poisoning. A possible explanation is the accumulation of phenols and hydroquinone in the target organ—the bone marrow—and subsequent oxidation of these metabolites to reactive quinone metabolites via a number of possible pathways. [11] A case-control study conducted in China showed that patients with two copies of the NQO1 C609T (NQO1*2 polymorphism) mutation had a 7.6-fold increased risk of benzene poisoning compared to those who carried one or two wild-type NQO1 alleles. [27]
Oxidative stress has been linked to onset of Alzheimer's disease (AD) [28] Since the NQO1*2 polymorphism affects the NQO1 activity and hence increase in oxidative stress, it has been postulated that this might increase the susceptibility of affected subjects for developing AD. A study conducted with a Chinese population consisting of 104 LOAD patients and 128 control patients disproved this hypothesis. [29]
Meta-analyses have been performed to examine the association between NQO1 polymorphism and increased cancer risk. [19] The results from some of these analyses have been summarized in the table below:
Cancer Type | Polymorphism | Risk Odds Ratio (95% Confidence Interval) | Reference |
---|---|---|---|
Prostate | C609T | All ethnicities: No significant change Asians: 1.419 (1.1053-1.913) | [30] |
Acute Lymphoblastic Leukemia | C609T | All ethnicities: 1.46 (1.18-1.79) Non-Asians 1.74 (1.29-2.36) | [31] |
Breast | C609T | All ethnicities: No significant change Caucasians: 1.177 (1.041-1.331) | [32] |
Colorectal | C609T | All ethnicities: 1.34 (1.10-1.64) | [33] |
Bladder | C609T | All ethnicities: 1.18 (1.06-1.31) | [34] |
De novo childhood leukemia | C609T | All ethnicities: 1.58 (1.22-2.07) Europeans, Asians: 1.52 (1.05-2.19) | [35] |
p53, also known as Tumor protein P53, cellular tumor antigen p53, or transformation-related protein 53 (TRP53) is a regulatory protein that is often mutated in human cancers. The p53 proteins are crucial in vertebrates, where they prevent cancer formation. As such, p53 has been described as "the guardian of the genome" because of its role in conserving stability by preventing genome mutation. Hence TP53 is classified as a tumor suppressor gene.
Ubiquitin is a small regulatory protein found in most tissues of eukaryotic organisms, i.e., it is found ubiquitously. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the late 1970s and 1980s. Four genes in the human genome code for ubiquitin: UBB, UBC, UBA52 and RPS27A.
Dihydrolipoamide dehydrogenase (DLD), also known as dihydrolipoyl dehydrogenase, mitochondrial, is an enzyme that in humans is encoded by the DLD gene. DLD is a flavoprotein enzyme that oxidizes dihydrolipoamide to lipoamide.
Xanthine dehydrogenase, also known as XDH, is a protein that, in humans, is encoded by the XDH gene.
Nuclear factor erythroid 2-related factor 2 (NRF2), also known as nuclear factor erythroid-derived 2-like 2, is a transcription factor that in humans is encoded by the NFE2L2 gene. NRF2 is a basic leucine zipper (bZIP) protein that may regulate the expression of antioxidant proteins that protect against oxidative damage triggered by injury and inflammation, according to preliminary research. In vitro, NRF2 binds to antioxidant response elements (AREs) in the promoter regions of genes encoding cytoprotective proteins. NRF2 induces the expression of heme oxygenase 1 in vitro leading to an increase in phase II enzymes. NRF2 also inhibits the NLRP3 inflammasome.
E3 ubiquitin-protein ligase SIAH1 is an enzyme that in humans is encoded by the SIAH1 gene.
In enzymology, a ribosyldihydronicotinamide dehydrogenase (quinone) (EC 1.10.99.2) is an enzyme that catalyzes the chemical reaction
In enzymology, a NAD(P)H dehydrogenase (quinone) (EC 1.6.5.2) is an enzyme that catalyzes the chemical reaction
Methionine synthase reductase, also known as MSR, is an enzyme that in humans is encoded by the MTRR gene.
NAD(P)H dehydrogenase, quinone 2, also known as QR2, is a protein that in humans is encoded by the NQO2 gene. It is a phase II detoxification enzyme which can carry out two or four electron reductions of quinones. Its mechanism of reduction is through a ping-pong mechanism involving its FAD cofactor. Initially in a reductive phase NQO2 binds to reduced dihydronicotinamide riboside (NRH) electron donor, and mediates a hydride transfer from NRH to FAD. Then, in an oxidative phase, NQO2 binds to its quinone substrate and reduces the quinone to a dihydroquinone. Besides the two catalytic FAD, NQO2 also has two zinc ions. It is not clear whether the metal has a catalytic role. NQO2 is a paralog of NQO1.
Carbonyl reductase 1, also known as CBR1, is an enzyme which in humans is encoded by the CBR1 gene. The protein encoded by this gene belongs to the short-chain dehydrogenases/reductases (SDR) family, which function as NADPH-dependent oxidoreductases having wide specificity for carbonyl compounds, such as quinones, prostaglandins, and various xenobiotics. Alternatively spliced transcript variants have been found for this gene.
Delta-1-pyrroline-5-carboxylate dehydrogenase, mitochondrial is an enzyme that in humans is encoded by the ALDH4A1 gene.
Putative quinone oxidoreductase is an enzyme that in humans is encoded by the TP53I3 gene.
Apoptosis-inducing factor 2 (AIFM2), also known as ferroptosis suppressor protein 1 (FSP1), apoptosis-inducing factor-homologous mitochondrion-associated inducer of death (AMID), is a protein that in humans is encoded by the AIFM2 gene, also known as p53-responsive gene 3 (PRG3), on chromosome 10.
CYP27C1 is a protein that in humans is encoded by the CYP27C1 gene. The Enzyme Commission number (EC) for this protein is EC 1.14.19.53. The full accepted name is all-trans-retinol 3,4-desaturase and the EC number 1 classifies CYP27C1 as a oxidoreductase that acts on paired donor by reducing oxygen. It is also identifiable by the UniProt code Q4G0S4.
Renalase, FAD-dependent amine oxidase is an enzyme that in humans is encoded by the RNLS gene. Renalase is a flavin adenine dinucleotide-dependent amine oxidase that is secreted into the blood from the kidney.
NADH:ubiquinone reductase (non-electrogenic) (EC 1.6.5.9, NDH-2, ubiquinone reductase, coenzyme Q reductase, dihydronicotinamide adenine dinucleotide-coenzyme Q reductase, DPNH-coenzyme Q reductase, DPNH-ubiquinone reductase, NADH-coenzyme Q oxidoreductase, NADH-coenzyme Q reductase, NADH-CoQ oxidoreductase, NADH-CoQ reductase) is an enzyme with systematic name NADH:ubiquinone oxidoreductase. This enzyme catalyses the following chemical reaction:
Hydroquinone 1,2-dioxygenase (EC 1.13.11.66, hydroquinone dioxygenase) is an enzyme with systematic name benzene-1,4-diol:oxygen 1,2-oxidoreductase (decyclizing). This enzyme catalyses the following chemical reaction
WRAP53 is a gene implicated in cancer development. The name was coined in 2009 to describe the dual role of this gene, encoding both an antisense RNA that regulates the p53 tumor suppressor and a protein involved in DNA repair, telomere elongation and maintenance of nuclear organelles Cajal bodies.
Jasvinder K Gambhir is an Indian doctor, researcher and professor in the fields of clinical biochemistry, diabetology and cardiology. Dr Gambhir completed her master's in biochemistry in 1972 from Punjab University and PhD from Post Graduate Institute of Medical Education and Research She has an experience in the field of over 40 years. She is Senior professor and Head of Department, Biochemistry at University College of Medical Sciences, New Delhi and Senior Professor at School of Medical Sciences and Research Noida. Dr. Gambhir is also a member of American Association of Clinical Chemistry (AACC).
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ignored (help)This article incorporates text from the United States National Library of Medicine, which is in the public domain.