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Hille R, Niks D. Application of EPR and related methods to molybdenum-containing enzymes. Methods Enzymol 2022; 666:373-412. [PMID: 35465925 DOI: 10.1016/bs.mie.2022.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A description is provided of the contributions made to our understanding of molybdenum-containing enzymes through the application of electron paramagnetic resonance spectroscopy and related methods, by way of illustrating how these can be applied to better understand enzyme structure and function. An emphasis is placed on the use of EPR to identify both the coordination environment of the molybdenum coordination sphere as well as the structures of paramagnetic intermediates observed transiently in the course of reaction that have led to the elucidation of reaction mechanism.
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, CA, United States.
| | - Dimitri Niks
- Department of Biochemistry, University of California, Riverside, CA, United States
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2
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Paragas EM, Choughule K, Jones JP, Barr JT. Enzyme Kinetics, Pharmacokinetics, and Inhibition of Aldehyde Oxidase. Methods Mol Biol 2021; 2342:257-284. [PMID: 34272698 DOI: 10.1007/978-1-0716-1554-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Aldehyde oxidase (AO) has emerged as an important drug metabolizing enzyme over the last decade. Several compounds have failed in the clinic because the clearance or toxicity was underestimated by preclinical species. Human AO is much more active than rodent AO, and dogs do not have functional AO. Metabolic products from AO-catalyzed oxidation are generally nonreactive and often they have much lower solubility. AO metabolism is not limited to oxidation as AO can also catalyze reduction of oxygen and nitrite. Reduction of oxygen leads to the reactive oxygen species (ROS) superoxide radical anion and hydrogen peroxide. Reduction of nitrite leads to the formation of nitric oxide with potential pharmacological implications. AO is also reported to catalyze the reductive metabolism of nitro-compounds, N-oxides, sulfoxides, isoxazoles, isothiazoles, nitrite, and hydroxamic acids. These reductive transformations may cause toxicity due to the formation of reactive metabolites. Moreover, the inhibition kinetics are complex, and multiple probe substrates should be used when assessing the potential for DDIs. Finally, AO appears to be amenable to computational predictions of both regioselectivity and rates of reaction, which holds promise for virtual screening.
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Affiliation(s)
- Erickson M Paragas
- Department of Pharmaceutical Sciences, Temple University School of Pharmacy, Philadelphia, PA, USA
| | - Kanika Choughule
- Pharmacokinetics, Pharmacodynamics and Drug Metabolism, Merck, Boston, MA, USA
| | - Jeffrey P Jones
- Department of Chemistry, Washington State University, Pullman, WA, USA
| | - John T Barr
- Pharmacokinetics, Pharmacodynamics and Drug Metabolism, Merck, South San Francisco, CA, USA.
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3
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Zhang Y, Yang Y, Shen G, Mao X, Jiao M, Lin Y. Identification and Characterization of Aldehyde Oxidase 5 in the Pheromone Gland of the Silkworm (Lepidoptera: Bombycidae). JOURNAL OF INSECT SCIENCE (ONLINE) 2020; 20:6029056. [PMID: 33295983 PMCID: PMC7724976 DOI: 10.1093/jisesa/ieaa132] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Indexed: 06/12/2023]
Abstract
Aldehyde oxidases (AOXs) are a subfamily of cytosolic molybdo-flavoenzymes that play critical roles in the detoxification and degradation of chemicals. Active AOXs, such as AOX1 and AOX2, have been identified and functionally analyzed in insect antennae but are rarely reported in other tissues. This is the first study to isolate and characterize the cDNA that encodes aldehyde oxidase 5 (BmAOX5) in the pheromone gland (PG) of the silkworm, Bombyx mori. The size of BmAOX5 cDNA is 3,741 nucleotides and includes an open reading frame, which encodes a protein of 1,246 amino acid residues. The theoretical molecular weight and isoelectric point of BmAOX5 are approximately 138 kDa and 5.58, respectively. BmAOX5 shares a similar primary structure with BmAOX1 and BmAOX2, containing two [2Fe-2S] redox centers, a FAD-binding domain, and a molybdenum cofactor (MoCo)-binding domain. RT-PCR revealed BmAOX5 to be particularly highly expressed in the PG (including ovipositor) of the female silkworm moth, and the expression was further confirmed by in situ hybridization, AOX activity staining, and anti-BmAOX5 western blotting. Further, BmAOX5 was shown to metabolize aromatic aldehydes, such as benzaldehyde, salicylaldehyde, and vanillic aldehyde, and fatty aldehydes, such as heptaldehyde and propionaldehyde. The maximum reaction rate (Vmax) of benzaldehyde as substrate was 21 mU and Km was 1.745 mmol/liter. These results suggested that BmAOX5 in the PG could metabolize aldehydes in the cytoplasm for detoxification or participate in the degradation of aldehyde pheromone substances and odorant compounds to identify mating partners and locate suitable spawning sites.
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Affiliation(s)
- Yandi Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Biological Science Research Center, Southwest University, Chongqing, China
| | - Yu Yang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Biological Science Research Center, Southwest University, Chongqing, China
| | - Guanwang Shen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericulture Science, Chongqing, China
- Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing, China
| | - Xueqin Mao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Biological Science Research Center, Southwest University, Chongqing, China
| | - Mengyao Jiao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Biological Science Research Center, Southwest University, Chongqing, China
| | - Ying Lin
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericulture Science, Chongqing, China
- Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing, China
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4
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Terao M, Garattini E, Romão MJ, Leimkühler S. Evolution, expression, and substrate specificities of aldehyde oxidase enzymes in eukaryotes. J Biol Chem 2020; 295:5377-5389. [PMID: 32144208 PMCID: PMC7170512 DOI: 10.1074/jbc.rev119.007741] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aldehyde oxidases (AOXs) are a small group of enzymes belonging to the larger family of molybdo-flavoenzymes, along with the well-characterized xanthine oxidoreductase. The two major types of reactions that are catalyzed by AOXs are the hydroxylation of heterocycles and the oxidation of aldehydes to their corresponding carboxylic acids. Different animal species have different complements of AOX genes. The two extremes are represented in humans and rodents; whereas the human genome contains a single active gene (AOX1), those of rodents, such as mice, are endowed with four genes (Aox1-4), clustering on the same chromosome, each encoding a functionally distinct AOX enzyme. It still remains enigmatic why some species have numerous AOX enzymes, whereas others harbor only one functional enzyme. At present, little is known about the physiological relevance of AOX enzymes in humans and their additional forms in other mammals. These enzymes are expressed in the liver and play an important role in the metabolisms of drugs and other xenobiotics. In this review, we discuss the expression, tissue-specific roles, and substrate specificities of the different mammalian AOX enzymes and highlight insights into their physiological roles.
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Affiliation(s)
- Mineko Terao
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, via La Masa 19, 20156 Milano, Italy
| | - Enrico Garattini
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, via La Masa 19, 20156 Milano, Italy
| | - Maria João Romão
- UCIBIO-Applied Biomolecular Sciences Unit, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Silke Leimkühler
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.
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5
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Beedle MT, Stevison F, Zhong G, Topping T, Hogarth C, Isoherranen N, Griswold MD. Sources of all-trans retinal oxidation independent of the aldehyde dehydrogenase 1A isozymes exist in the postnatal testis†. Biol Reprod 2020; 100:547-560. [PMID: 30247516 DOI: 10.1093/biolre/ioy200] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 08/01/2018] [Accepted: 09/11/2018] [Indexed: 02/06/2023] Open
Abstract
Despite the essential role of the active metabolite of vitamin A, all-trans retinoic acid (atRA) in spermatogenesis, the enzymes, and cellular populations responsible for its synthesis in the postnatal testis remain largely unknown. The aldehyde dehydrogenase 1A (ALDH1A) family of enzymes residing within Sertoli cells is responsible for the synthesis of atRA, driving the first round of spermatogenesis. Those studies also revealed that the atRA required to drive subsequent rounds of spermatogenesis is possibly derived from the ALDH1A enzymes residing within the meiotic and post-meiotic germ cells. Three ALDH1A isozymes (ALDH1A1, ALDH1A2, and ALDH1A3) are present in the testis. Although, ALDH1A1 is expressed in adult Sertoli cells and is suggested to contribute to the atRA required for the pre-meiotic transitions, ALDH1A2 is proposed to be the essential isomer involved in testicular atRA biosynthesis. In this report, we first examine the requirement for ALDH1A2 via the generation and analysis of a conditional Aldh1a2 germ cell knockout and a tamoxifen-induced Aldh1a2 knockout model. We then utilized the pan-ALDH1A inhibitor (WIN 18446) to test the collective contribution of the ALDH1A enzymes to atRA biosynthesis following the first round of spermatogenesis. Collectively, our data provide the first in vivo evidence demonstrating that animals severely deficient in ALDH1A2 postnatally proceed normally through spermatogenesis. Our studies with a pan-ALDH1A inhibitor (WIN 18446) also suggest that an alternative source of atRA biosynthesis independent of the ALDH1A enzymes becomes available to maintain atRA levels for several spermatogenic cycles following an initial atRA injection.
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Affiliation(s)
- My-Thanh Beedle
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, Washington, USA
| | - Faith Stevison
- Department of Pharmaceutics, University of Washington, Seattle, Washington, USA
| | - Guo Zhong
- Department of Pharmaceutics, University of Washington, Seattle, Washington, USA
| | - Traci Topping
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, Washington, USA
| | - Cathryn Hogarth
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, Washington, USA
| | - Nina Isoherranen
- Department of Pharmaceutics, University of Washington, Seattle, Washington, USA
| | - Michael D Griswold
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, Washington, USA
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6
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Manevski N, King L, Pitt WR, Lecomte F, Toselli F. Metabolism by Aldehyde Oxidase: Drug Design and Complementary Approaches to Challenges in Drug Discovery. J Med Chem 2019; 62:10955-10994. [PMID: 31385704 DOI: 10.1021/acs.jmedchem.9b00875] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Aldehyde oxidase (AO) catalyzes oxidations of azaheterocycles and aldehydes, amide hydrolysis, and diverse reductions. AO substrates are rare among marketed drugs, and many candidates failed due to poor pharmacokinetics, interspecies differences, and adverse effects. As most issues arise from complex and poorly understood AO biology, an effective solution is to stop or decrease AO metabolism. This perspective focuses on rational drug design approaches to modulate AO-mediated metabolism in drug discovery. AO biological aspects are also covered, as they are complementary to chemical design and important when selecting the experimental system for risk assessment. The authors' recommendation is an early consideration of AO-mediated metabolism supported by computational and in vitro experimental methods but not an automatic avoidance of AO structural flags, many of which are versatile and valuable building blocks. Preferably, consideration of AO-mediated metabolism should be part of the multiparametric drug optimization process, with the goal to improve overall drug-like properties.
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Affiliation(s)
- Nenad Manevski
- UCB Celltech , 208 Bath Road , Slough SL13WE , United Kingdom
| | - Lloyd King
- UCB Celltech , 208 Bath Road , Slough SL13WE , United Kingdom
| | - William R Pitt
- UCB Celltech , 208 Bath Road , Slough SL13WE , United Kingdom
| | - Fabien Lecomte
- UCB Celltech , 208 Bath Road , Slough SL13WE , United Kingdom
| | - Francesca Toselli
- UCB BioPharma , Chemin du Foriest 1 , 1420 Braine-l'Alleud , Belgium
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7
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Dalvie D, Di L. Aldehyde oxidase and its role as a drug metabolizing enzyme. Pharmacol Ther 2019; 201:137-180. [PMID: 31128989 DOI: 10.1016/j.pharmthera.2019.05.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 03/27/2019] [Indexed: 11/29/2022]
Abstract
Aldehyde oxidase (AO) is a cytosolic enzyme that belongs to the family of structurally related molybdoflavoproteins like xanthine oxidase (XO). The enzyme is characterized by broad substrate specificity and marked species differences. It catalyzes the oxidation of aromatic and aliphatic aldehydes and various heteroaromatic rings as well as reduction of several functional groups. The references to AO and its role in metabolism date back to the 1950s, but the importance of this enzyme in the metabolism of drugs has emerged in the past fifteen years. Several reviews on the role of AO in drug metabolism have been published in the past decade indicative of the growing interest in the enzyme and its influence in drug metabolism. Here, we present a comprehensive monograph of AO as a drug metabolizing enzyme with emphasis on marketed drugs as well as other xenobiotics, as substrates and inhibitors. Although the number of drugs that are primarily metabolized by AO are few, the impact of AO on drug development has been extensive. We also discuss the effect of AO on the systemic exposure and clearance these clinical candidates. The review provides a comprehensive analysis of drug discovery compounds involving AO with the focus on developmental candidates that were reported in the past five years with regards to pharmacokinetics and toxicity. While there is only one known report of AO-mediated clinically relevant drug-drug interaction (DDI), a detailed description of inhibitors and inducers of AO known to date has been presented here and the potential risks associated with DDI. The increasing recognition of the importance of AO has led to significant progress in predicting the site of AO-mediated metabolism using computational methods. Additionally, marked species difference in expression of AO makes it is difficult to predict human clearance with high confidence. The progress made towards developing in vivo, in vitro and in silico approaches for predicting AO metabolism and estimating human clearance of compounds that are metabolized by AO have also been discussed.
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Affiliation(s)
- Deepak Dalvie
- Drug Metabolism and Pharmacokinetics, Celgene Corporation, 10300, Campus Point Drive, San Diego, CA 92121, USA.
| | - Li Di
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, CT 06340, UK
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8
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Takaoka N, Sanoh S, Okuda K, Kotake Y, Sugahara G, Yanagi A, Ishida Y, Tateno C, Tayama Y, Sugihara K, Kitamura S, Kurosaki M, Terao M, Garattini E, Ohta S. Inhibitory effects of drugs on the metabolic activity of mouse and human aldehyde oxidases and influence on drug–drug interactions. Biochem Pharmacol 2018; 154:28-38. [DOI: 10.1016/j.bcp.2018.04.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 04/16/2018] [Indexed: 12/19/2022]
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9
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Mota C, Coelho C, Leimkühler S, Garattini E, Terao M, Santos-Silva T, Romão MJ. Critical overview on the structure and metabolism of human aldehyde oxidase and its role in pharmacokinetics. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.04.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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10
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Direct comparison of the four aldehyde oxidase enzymes present in mouse gives insight into their substrate specificities. PLoS One 2018; 13:e0191819. [PMID: 29370288 PMCID: PMC5784979 DOI: 10.1371/journal.pone.0191819] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/11/2018] [Indexed: 12/13/2022] Open
Abstract
Mammalian aldehyde oxidases (AOXs) are molybdo-flavoenzymes which are present in many tissues in various mammalian species, including humans and rodents. Different species contain a different number of AOX isoforms. In particular, the reasons why mammals other than humans express a multiplicity of tissue-specific AOX enzymes is unknown. In mouse, the isoforms mAOX1, mAOX3, mAOX4 and mAOX2 are present. We previously established a codon-optimized heterologous expression systems for the mAOX1-4 isoforms in Escherichia coli that gives yield to sufficient amounts of active protein for kinetic characterizations and sets the basis in this study for site-directed mutagenesis and structure-function studies. A direct and simultaneous comparison of the enzymatic properties and characteristics of the four enzymes on a larger number of substrates has never been performed. Here, thirty different structurally related aromatic, aliphatic and N-heterocyclic compounds were used as substrates, and the kinetic parameters of all four mAOX enzymes were directly compared. The results show that especially mAOX4 displays a higher substrate selectivity, while no major differences between mAOX1, mAOX2 and mAOX3 were identified. Generally, mAOX1 was the enzyme with the highest catalytic turnover for most substrates. To understand the factors that contribute to the substrate specificity of mAOX4, site-directed mutagenesis was applied to substitute amino acids in the substrate-binding funnel by the ones present in mAOX1, mAOX3, and mAOX2. An increase in activity was obtained by the amino acid exchange M1088V in the active site identified to be specific for mAOX4, to the amino acid identified in mAOX3.
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11
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Kücükgöze G, Terao M, Garattini E, Leimkühler S. Direct Comparison of the Enzymatic Characteristics and Superoxide Production of the Four Aldehyde Oxidase Enzymes Present in Mouse. Drug Metab Dispos 2017; 45:947-955. [DOI: 10.1124/dmd.117.075937] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/15/2017] [Indexed: 11/22/2022] Open
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12
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Sussmilch FC, Brodribb TJ, McAdam SAM. What are the evolutionary origins of stomatal responses to abscisic acid in land plants? JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:240-260. [PMID: 28093875 DOI: 10.1111/jipb.12523] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 01/15/2017] [Indexed: 05/20/2023]
Abstract
The evolution of active stomatal closure in response to leaf water deficit, mediated by the hormone abscisic acid (ABA), has been the subject of recent debate. Two different models for the timing of the evolution of this response recur in the literature. A single-step model for stomatal control suggests that stomata evolved active, ABA-mediated control of stomatal aperture, when these structures first appeared, prior to the divergence of bryophyte and vascular plant lineages. In contrast, a gradualistic model for stomatal control proposes that the most basal vascular plant stomata responded passively to changes in leaf water status. This model suggests that active ABA-driven mechanisms for stomatal responses to water status instead evolved after the divergence of seed plants, culminating in the complex, ABA-mediated responses observed in modern angiosperms. Here we review the findings that form the basis for these two models, including recent work that provides critical molecular insights into resolving this intriguing debate, and find strong evidence to support a gradualistic model for stomatal evolution.
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Affiliation(s)
- Frances C Sussmilch
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
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13
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Terao M, Barzago MM, Kurosaki M, Fratelli M, Bolis M, Borsotti A, Bigini P, Micotti E, Carli M, Invernizzi RW, Bagnati R, Passoni A, Pastorelli R, Brunelli L, Toschi I, Cesari V, Sanoh S, Garattini E. Mouse aldehyde-oxidase-4 controls diurnal rhythms, fat deposition and locomotor activity. Sci Rep 2016; 6:30343. [PMID: 27456060 PMCID: PMC4960552 DOI: 10.1038/srep30343] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 06/30/2016] [Indexed: 02/03/2023] Open
Abstract
Aldehyde-oxidase-4 (AOX4) is one of the mouse aldehyde oxidase isoenzymes and its physiological function is unknown. The major source of AOX4 is the Harderian-gland, where the enzyme is characterized by daily rhythmic fluctuations. Deletion of the Aox4 gene causes perturbations in the expression of the circadian-rhythms gene pathway, as indicated by transcriptomic analysis. AOX4 inactivation alters the diurnal oscillations in the expression of master clock-genes. Similar effects are observed in other organs devoid of AOX4, such as white adipose tissue, liver and hypothalamus indicating a systemic action. While perturbations of clock-genes is sex-independent in the Harderian-gland and hypothalamus, sex influences this trait in liver and white-adipose-tissue which are characterized by the presence of AOX isoforms other than AOX4. In knock-out animals, perturbations in clock-gene expression are accompanied by reduced locomotor activity, resistance to diet induced obesity and to hepatic steatosis. All these effects are observed in female and male animals. Resistance to obesity is due to diminished fat accumulation resulting from increased energy dissipation, as white-adipocytes undergo trans-differentiation towards brown-adipocytes. Metabolomics and enzymatic data indicate that 5-hydroxyindolacetic acid and tryptophan are novel endogenous AOX4 substrates, potentially involved in AOX4 systemic actions.
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Affiliation(s)
- Mineko Terao
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Maria Monica Barzago
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Mami Kurosaki
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Maddalena Fratelli
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Marco Bolis
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Andrea Borsotti
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Paolo Bigini
- Laboratory of Biochemistry and Protein Chemistry, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Edoardo Micotti
- Laboratory of Neurodegenerative diseases, Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Mirjana Carli
- Laboratory of Neurochemistry and Behaviour, Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Roberto William Invernizzi
- Laboratory of Neurochemistry and Behaviour, Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Renzo Bagnati
- Analytical Instrumentation Unit, Department of Environmental Health Sciences, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Alice Passoni
- Analytical Instrumentation Unit, Department of Environmental Health Sciences, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Roberta Pastorelli
- Laboratory of Mass Spectrometry, Department of Environmental Health Sciences; IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Laura Brunelli
- Laboratory of Mass Spectrometry, Department of Environmental Health Sciences; IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
| | - Ivan Toschi
- Department of Agricultural and Environmental Sciences; Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy
| | - Valentina Cesari
- Department of Agricultural and Environmental Sciences; Università degli Studi di Milano, via Celoria 2, 20133 Milano, Italy
| | - Seigo Sanoh
- Graduate School of Biochemical and Health Sciences, Hiroshima University, Hiroshima Japan
| | - Enrico Garattini
- Laboratory of Molecular Biology, Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", via La Masa 19, 20156, Milano, Italy
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14
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Structure and function of mammalian aldehyde oxidases. Arch Toxicol 2016; 90:753-80. [DOI: 10.1007/s00204-016-1683-1] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 02/16/2016] [Indexed: 12/12/2022]
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15
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Maia LB, Pereira V, Mira L, Moura JJG. Nitrite reductase activity of rat and human xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: evaluation of their contribution to NO formation in vivo. Biochemistry 2015; 54:685-710. [PMID: 25537183 DOI: 10.1021/bi500987w] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nitrite is presently considered a NO "storage form" that can be made available, through its one-electron reduction, to maintain NO formation under hypoxia/anoxia. The molybdoenzymes xanthine oxidase/dehydrogenase (XO/XD) and aldehyde oxidase (AO) are two of the most promising mammalian nitrite reductases, and in this work, we characterized NO formation by rat and human XO/XD and AO. This is the first characterization of human enzymes, and our results support the employment of rat liver enzymes as suitable models of the human counterparts. A comprehensive kinetic characterization of the effect of pH on XO and AO-catalyzed nitrite reduction showed that the enzyme's specificity constant for nitrite increase 8-fold, while the Km(NO2(-)) decrease 6-fold, when the pH decreases from 7.4 to 6.3. These results demonstrate that the ability of XO/AO to trigger NO formation would be greatly enhanced under the acidic conditions characteristic of ischemia. The dioxygen inhibition was quantified, and the Ki(O2) values found (24.3-48.8 μM) suggest that in vivo NO formation would be fine-tuned by dioxygen availability. The potential in vivo relative physiological relevance of XO/XD/AO-dependent pathways of NO formation was evaluated using HepG2 and HMEC cell lines subjected to hypoxia. NO formation by the cells was found to be pH-, nitrite-, and dioxygen-dependent, and the relative contribution of XO/XD plus AO was found to be as high as 50%. Collectively, our results supported the possibility that XO/XD and AO can contribute to NO generation under hypoxia inside a living human cell. Furthermore, the molecular mechanism of XO/AO-catalyzed nitrite reduction was revised.
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Affiliation(s)
- Luisa B Maia
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa , 2829-516 Caparica, Portugal
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - James Hall
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
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Barr JT, Choughule K, Jones JP. Enzyme kinetics, inhibition, and regioselectivity of aldehyde oxidase. Methods Mol Biol 2014; 1113:167-186. [PMID: 24523113 DOI: 10.1007/978-1-62703-758-7_9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The aldehyde oxidase (AO) enzyme family plays an increasing role in drug development. However, a number of compounds that are AO substrates have failed in the clinic because the clearance or toxicity is underestimated by preclinical species. Human AO is much more active than rodent AO, and dogs do not have functional AO. While AOs normally make non-reactive metabolites such as lactams, the metabolic products often have much lower solubility that can lead to renal failure. While an endogenous substrate for the oxidation reaction is not known, electron acceptors for the reductive part of the reaction include oxygen and nitrites. Reduction of oxygen leads to the reactive oxygen species (ROS) superoxide radical anion, and hydrogen peroxide. Reduction of nitrite leads to the formation of nitric oxide with potential pharmacological implications. To date, no clinically important drug-drug interactions (DDIs) have been observed for AOs. However, the inhibition kinetics are complex, and multiple probe substrates should be used when assessing the potential for DDIs. Finally, AO appears to be amenable to computational predictions of both regioselectivity and rates of reaction, which holds promise for virtual screening.
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Affiliation(s)
- John T Barr
- Department of Chemistry, Washington State University, Pullman, WA, USA
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Kurosaki M, Bolis M, Fratelli M, Barzago MM, Pattini L, Perretta G, Terao M, Garattini E. Structure and evolution of vertebrate aldehyde oxidases: from gene duplication to gene suppression. Cell Mol Life Sci 2013; 70:1807-30. [PMID: 23263164 PMCID: PMC11113236 DOI: 10.1007/s00018-012-1229-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/29/2012] [Accepted: 12/03/2012] [Indexed: 12/20/2022]
Abstract
Aldehyde oxidases (AOXs) and xanthine dehydrogenases (XDHs) belong to the family of molybdo-flavoenzymes. Although AOXs are not identifiable in fungi, these enzymes are represented in certain protists and the majority of plants and vertebrates. The physiological functions and substrates of AOXs are unknown. Nevertheless, AOXs are major drug metabolizing enzymes, oxidizing a wide range of aromatic aldehydes and heterocyclic compounds of medical/toxicological importance. Using genome sequencing data, we predict the structures of AOX genes and pseudogenes, reconstructing their evolution. Fishes are the most primitive organisms with an AOX gene (AOXα), originating from the duplication of an ancestral XDH. Further evolution of fishes resulted in the duplication of AOXα into AOXβ and successive pseudogenization of AOXα. AOXβ is maintained in amphibians and it is the likely precursors of reptilian, avian, and mammalian AOX1. Amphibian AOXγ is a duplication of AOXβ and the likely ancestor of reptilian and avian AOX2, which, in turn, gave rise to mammalian AOX3L1. Subsequent gene duplications generated the two mammalian genes, AOX3 and AOX4. The evolution of mammalian AOX genes is dominated by pseudogenization and deletion events. Our analysis is relevant from a structural point of view, as it provides information on the residues characterizing the three domains of each mammalian AOX isoenzyme. We cloned the cDNAs encoding the AOX proteins of guinea pig and cynomolgus monkeys, two unique species as to the evolution of this enzyme family. We identify chimeric RNAs from the human AOX3 and AOX3L1 pseudogenes with potential to encode a novel microRNA.
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Affiliation(s)
- Mami Kurosaki
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche “Mario Negri”, via La Masa 19, 20156 Milan, Italy
| | - Marco Bolis
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche “Mario Negri”, via La Masa 19, 20156 Milan, Italy
| | - Maddalena Fratelli
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche “Mario Negri”, via La Masa 19, 20156 Milan, Italy
| | - Maria Monica Barzago
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche “Mario Negri”, via La Masa 19, 20156 Milan, Italy
| | - Linda Pattini
- Department of Bioengineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
| | - Gemma Perretta
- Istututo di Biologia Cellulare e Neurobiologia, Consiglio Nazionale delle Ricerche, via Anguillarese 301, 00123 Rome, Italy
| | - Mineko Terao
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche “Mario Negri”, via La Masa 19, 20156 Milan, Italy
| | - Enrico Garattini
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche “Mario Negri”, via La Masa 19, 20156 Milan, Italy
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Garattini E, Terao M. Aldehyde oxidase and its importance in novel drug discovery: present and future challenges. Expert Opin Drug Discov 2013; 8:641-54. [DOI: 10.1517/17460441.2013.788497] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Zarepour M, Simon K, Wilch M, Nieländer U, Koshiba T, Seo M, Lindel T, Bittner F. Identification of superoxide production by Arabidopsis thaliana aldehyde oxidases AAO1 and AAO3. PLANT MOLECULAR BIOLOGY 2012; 80:659-71. [PMID: 23065119 DOI: 10.1007/s11103-012-9975-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 09/28/2012] [Indexed: 05/07/2023]
Abstract
Plant aldehyde oxidases (AOs) have gained great attention during the last years as they catalyze the last step in the biosynthesis of the phytohormone abscisic acid by oxidation of abscisic aldehyde. Furthermore, oxidation of indole-3-acetaldehyde by AOs is likely to represent one route to produce another phytohormone, indole-3-acetic acid, and thus, AOs play important roles in many aspects of plant growth and development. In the present work we demonstrate that heterologously expressed AAO1 and AAO3, two prominent members of the AO family from Arabidopsis thaliana, do not only generate hydrogen peroxide but also superoxide anions by transferring aldehyde-derived electrons to molecular oxygen. In support of this, superoxide production has also been found for native AO proteins in Arabidopsis leaf extracts. In addition to their aldehyde oxidation activity, AAO1 and AAO3 were found to exhibit NADH oxidase activity, which likewise is associated with the production of superoxide anions. According to these results and due to the fact that molecular oxygen is the only known physiological electron acceptor of AOs, the production of hydrogen peroxide and/or superoxide has to be considered in any physiological condition in which aldehydes or NADH serve as substrate for AOs. In this respect, conditions such as natural senescence and stress-induced stomatal movement, which both require simultaneously elevated levels of abscisic acid and hydrogen peroxide/superoxide, are likely to benefit from AOs in two ways, namely by formation of abscisic acid and by concomitant formation of reactive oxygen species.
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Affiliation(s)
- Maryam Zarepour
- Department of Plant Biology, Braunschweig University of Technology, Humboldtstrasse 1, 38106 Braunschweig, Germany
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Coelho C, Mahro M, Trincão J, Carvalho ATP, Ramos MJ, Terao M, Garattini E, Leimkühler S, Romão MJ. The first mammalian aldehyde oxidase crystal structure: insights into substrate specificity. J Biol Chem 2012; 287:40690-702. [PMID: 23019336 DOI: 10.1074/jbc.m112.390419] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Aldehyde oxidases have pharmacological relevance, and AOX3 is the major drug-metabolizing enzyme in rodents. RESULTS The crystal structure of mouse AOX3 with kinetics and molecular docking studies provides insights into its enzymatic characteristics. CONCLUSION Differences in substrate and inhibitor specificities can be rationalized by comparing the AOX3 and xanthine oxidase structures. SIGNIFICANCE The first aldehyde oxidase structure represents a major advance for drug design and mechanistic studies. Aldehyde oxidases (AOXs) are homodimeric proteins belonging to the xanthine oxidase family of molybdenum-containing enzymes. Each 150-kDa monomer contains a FAD redox cofactor, two spectroscopically distinct [2Fe-2S] clusters, and a molybdenum cofactor located within the protein active site. AOXs are characterized by broad range substrate specificity, oxidizing different aldehydes and aromatic N-heterocycles. Despite increasing recognition of its role in the metabolism of drugs and xenobiotics, the physiological function of the protein is still largely unknown. We have crystallized and solved the crystal structure of mouse liver aldehyde oxidase 3 to 2.9 Å. This is the first mammalian AOX whose structure has been solved. The structure provides important insights into the protein active center and further evidence on the catalytic differences characterizing AOX and xanthine oxidoreductase. The mouse liver aldehyde oxidase 3 three-dimensional structure combined with kinetic, mutagenesis data, molecular docking, and molecular dynamics studies make a decisive contribution to understand the molecular basis of its rather broad substrate specificity.
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Affiliation(s)
- Catarina Coelho
- Requimte, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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22
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Garattini E, Terao M. The role of aldehyde oxidase in drug metabolism. Expert Opin Drug Metab Toxicol 2012; 8:487-503. [DOI: 10.1517/17425255.2012.663352] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Mendel RR. Cell biology of molybdenum in plants. PLANT CELL REPORTS 2011; 30:1787-1797. [PMID: 21660547 DOI: 10.1007/s00299-011-1100-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 05/30/2011] [Accepted: 05/30/2011] [Indexed: 05/30/2023]
Abstract
The transition element molybdenum (Mo) is of essential importance for (nearly) all biological systems as it is required by enzymes catalyzing important reactions within the cell. The metal itself is biologically inactive unless it is complexed by a special cofactor. With the exception of bacterial nitrogenase, where Mo is a constituent of the FeMo-cofactor, Mo is bound to a pterin, thus forming the molybdenum cofactor (Moco) which is the active compound at the catalytic site of all other Mo-enzymes. In plants, the most prominent Mo-enzymes are nitrate reductase, sulfite oxidase, xanthine dehydrogenase, aldehyde oxidase, and the mitochondrial amidoxime reductase. The biosynthesis of Moco involves the complex interaction of six proteins and is a process of four steps, which also includes iron as well as copper in an indispensable way. After its synthesis, Moco is distributed to the apoproteins of Mo-enzymes by Moco-carrier/binding proteins that also participate in Moco-insertion into the cognate apoproteins. Xanthine dehydrogenase and aldehyde oxidase, but not the other Mo-enzymes, require a final step of posttranslational activation of their catalytic Mo-center for becoming active.
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Affiliation(s)
- Ralf R Mendel
- Department of Plant Biology, Braunschweig University of Technology, 38106, Braunschweig, Germany.
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Mahro M, Coelho C, Trincão J, Rodrigues D, Terao M, Garattini E, Saggu M, Lendzian F, Hildebrandt P, Romão MJ, Leimkühler S. Characterization and crystallization of mouse aldehyde oxidase 3: from mouse liver to Escherichia coli heterologous protein expression. Drug Metab Dispos 2011; 39:1939-45. [PMID: 21705476 DOI: 10.1124/dmd.111.040873] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Aldehyde oxidase (AOX) is characterized by a broad substrate specificity, oxidizing aromatic azaheterocycles, such as N¹-methylnicotinamide and N-methylphthalazinium, or aldehydes, such as benzaldehyde, retinal, and vanillin. In the past decade, AOX has been recognized increasingly to play an important role in the metabolism of drugs through its complex cofactor content, tissue distribution, and substrate recognition. In humans, only one AOX gene (AOX1) is present, but in mouse and other mammals different AOX homologs were identified. The multiple AOX isoforms are expressed tissue-specifically in different organisms, and it is believed that they recognize distinct substrates and carry out different physiological tasks. AOX is a dimer with a molecular mass of approximately 300 kDa, and each subunit of the homodimeric enzyme contains four different cofactors: the molybdenum cofactor, two distinct [2Fe-2S] clusters, and one FAD. We purified the AOX homolog from mouse liver (mAOX3) and established a system for the heterologous expression of mAOX3 in Escherichia coli. The purified enzymes were compared. Both proteins show the same characteristics and catalytic properties, with the difference that the recombinant protein was expressed and purified in a 30% active form, whereas the native protein is 100% active. Spectroscopic characterization showed that FeSII is not assembled completely in mAOX3. In addition, both proteins were crystallized. The best crystals were from native mAOX3 and diffracted beyond 2.9 Å. The crystals belong to space group P1, and two dimers are present in the unit cell.
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Affiliation(s)
- Martin Mahro
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
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Garattini E, Terao M. Increasing recognition of the importance of aldehyde oxidase in drug development and discovery. Drug Metab Rev 2011; 43:374-86. [DOI: 10.3109/03602532.2011.560606] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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26
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Wahl B, Reichmann D, Niks D, Krompholz N, Havemeyer A, Clement B, Messerschmidt T, Rothkegel M, Biester H, Hille R, Mendel RR, Bittner F. Biochemical and spectroscopic characterization of the human mitochondrial amidoxime reducing components hmARC-1 and hmARC-2 suggests the existence of a new molybdenum enzyme family in eukaryotes. J Biol Chem 2010; 285:37847-59. [PMID: 20861021 PMCID: PMC2988388 DOI: 10.1074/jbc.m110.169532] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 09/17/2010] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial amidoxime reducing component mARC is a newly discovered molybdenum enzyme that is presumed to form the catalytical part of a three-component enzyme system, consisting of mARC, heme/cytochrome b(5), and NADH/FAD-dependent cytochrome b(5) reductase. mARC proteins share a significant degree of homology to the molybdenum cofactor-binding domain of eukaryotic molybdenum cofactor sulfurase proteins, the latter catalyzing the post-translational activation of aldehyde oxidase and xanthine oxidoreductase. The human genome harbors two mARC genes, referred to as hmARC-1/MOSC-1 and hmARC-2/MOSC-2, which are organized in a tandem arrangement on chromosome 1. Recombinant expression of hmARC-1 and hmARC-2 proteins in Escherichia coli reveals that both proteins are monomeric in their active forms, which is in contrast to all other eukaryotic molybdenum enzymes that act as homo- or heterodimers. Both hmARC-1 and hmARC-2 catalyze the N-reduction of a variety of N-hydroxylated substrates such as N-hydroxy-cytosine, albeit with different specificities. Reconstitution of active molybdenum cofactor onto recombinant hmARC-1 and hmARC-2 proteins in the absence of sulfur indicates that mARC proteins do not belong to the xanthine oxidase family of molybdenum enzymes. Moreover, they also appear to be different from the sulfite oxidase family, because no cysteine residue could be identified as a putative ligand of the molybdenum atom. This suggests that the hmARC proteins and sulfurase represent members of a new family of molybdenum enzymes.
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Affiliation(s)
- Bettina Wahl
- From the Department of Plant Biology, Technische Universität Braunschweig, 38023 Braunschweig, Germany
| | - Debora Reichmann
- From the Department of Plant Biology, Technische Universität Braunschweig, 38023 Braunschweig, Germany
| | - Dimitri Niks
- the Department of Biochemistry, University of California, Riverside, California 92521
| | - Nina Krompholz
- the Pharmaceutical Institute, Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-Universität Kiel, 24118 Kiel, Germany, and
| | - Antje Havemeyer
- the Pharmaceutical Institute, Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-Universität Kiel, 24118 Kiel, Germany, and
| | - Bernd Clement
- the Pharmaceutical Institute, Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-Universität Kiel, 24118 Kiel, Germany, and
| | | | | | - Harald Biester
- Environmental Geology, Technische Universität Braunschweig, 38023 Braunschweig, Germany
| | - Russ Hille
- the Department of Biochemistry, University of California, Riverside, California 92521
| | - Ralf R. Mendel
- From the Department of Plant Biology, Technische Universität Braunschweig, 38023 Braunschweig, Germany
| | - Florian Bittner
- From the Department of Plant Biology, Technische Universität Braunschweig, 38023 Braunschweig, Germany
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Abstract
Aldehyde oxidases (EC 1.2.3.1) are a small group of structurally conserved cytosolic proteins represented in both the animal and plant kingdoms. In vertebrates, aldehyde oxidases constitute the small sub-family of molybdo-flavoenzymes, along with the evolutionarily and structurally related protein, xanthine oxidoreductase. These enzymes require a molybdo-pterin cofactor (molybdenum cofactor, MoCo) and flavin adenine dinucleotide for their catalytic activity. Aldehyde oxidases have broad substrate specificity and catalyse the hydroxylation of N-heterocycles and the oxidation of aldehydes to the corresponding acid. In humans, a single aldehyde oxidase gene (AOX1) and two pseudogenes clustering on a short stretch of chromosome 2q are known. In other mammals, a variable number of structurally conserved aldehyde oxidase genes has been described. Four genes (Aox1, Aox3, Aox4 and Aox3l1), coding for an equivalent number of catalytically active enzymes, are present in the mouse and rat genomes. Although human AOX1 and its homologous proteins are best known as drug metabolising enzymes, the physiological substrate(s) and function(s) are as yet unknown. The present paper provides an update of the available information on the evolutionary history, tissue- and cell-specific distribution and function of mammalian aldehyde oxidases.
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Affiliation(s)
- Enrico Garattini
- Laboratory of Molecular Biology, Department of Biochemistry and Molecular Pharmacology, Istituto di Ricerche Farmacologiche Mario Negri, via La Masa 19, 20156 Milano, Italy.
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Liu P, Liang S, Wang BJ, Guo RC. Construction of expression system of rabbit aldehyde oxidase cDNA for the clarification of species differences. Eur J Drug Metab Pharmacokinet 2009; 34:205-11. [DOI: 10.1007/bf03191175] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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30
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Abstract
The transition element molybdenum (Mo) is an essential micronutrient that is needed as catalytically active metal during enzyme catalysis. In humans four enzymes depend on Mo: sulfite oxidase, xanthine oxidoreductase, aldehyde oxidase, and mitochondrial amidoxime reductase. In addition to these enzymes, plants harbor a fifth Mo-enzyme namely nitrate reductase. To gain biological activity and fulfill its function in enzymes, Mo has to be complexed by a pterin compound thus forming the molybdenum cofactor. This article will review the way that Mo takes from uptake into the cell, via formation of the molybdenum cofactor and its storage, up to the final insertion of the molybdenum cofactor into apometalloenzymes.
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Affiliation(s)
- Ralf R Mendel
- Institute of Plant Biology, Braunschweig University of Technology, Braunschweig, Germany.
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Schumann S, Terao M, Garattini E, Saggu M, Lendzian F, Hildebrandt P, Leimkühler S. Site directed mutagenesis of amino acid residues at the active site of mouse aldehyde oxidase AOX1. PLoS One 2009; 4:e5348. [PMID: 19401776 PMCID: PMC2671166 DOI: 10.1371/journal.pone.0005348] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 03/30/2009] [Indexed: 12/04/2022] Open
Abstract
Mouse aldehyde oxidase (mAOX1) forms a homodimer and belongs to the xanthine oxidase family of molybdoenzymes which are characterized by an essential equatorial sulfur ligand coordinated to the molybdenum atom. In general, mammalian AOs are characterized by broad substrate specificity and an yet obscure physiological function. To define the physiological substrates and the enzymatic characteristics of mAOX1, we established a system for the heterologous expression of the enzyme in Eschericia coli. The recombinant protein showed spectral features and a range of substrate specificity similar to the native protein purified from mouse liver. The EPR data of recombinant mAOX1 were similar to those of AO from rabbit liver, but differed from the homologous xanthine oxidoreductase enzymes. Site-directed mutagenesis of amino acids Val806, Met884 and Glu1265 at the active site resulted in a drastic decrease in the oxidation of aldehydes with no increase in the oxidation of purine substrates. The double mutant V806E/M884R and the single mutant E1265Q were catalytically inactive enzymes regardless of the aldehyde or purine substrates tested. Our results show that only Glu1265 is essential for the catalytic activity by initiating the base-catalyzed mechanism of substrate oxidation. In addition, it is concluded that the substrate specificity of molybdo-flavoenzymes is more complex and not only defined by the three characterized amino acids in the active site.
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Affiliation(s)
- Silvia Schumann
- Universität Potsdam, Institut für Biochemie and Biologie, Potsdam, Germany
| | - Mineko Terao
- Department of Biochemistry and Molecular Pharmacology, Istituto de Ricerche Farmacologiche, “Mario Negri”, Milano, Italy
| | - Enrico Garattini
- Department of Biochemistry and Molecular Pharmacology, Istituto de Ricerche Farmacologiche, “Mario Negri”, Milano, Italy
| | - Miguel Saggu
- Technische Universität Berlin, Institut für Chemie, Berlin, Germany
| | | | | | - Silke Leimkühler
- Universität Potsdam, Institut für Biochemie and Biologie, Potsdam, Germany
- * E-mail:
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Role of the molybdoflavoenzyme aldehyde oxidase homolog 2 in the biosynthesis of retinoic acid: generation and characterization of a knockout mouse. Mol Cell Biol 2008; 29:357-77. [PMID: 18981221 DOI: 10.1128/mcb.01385-08] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The mouse aldehyde oxidase AOH2 (aldehyde oxidase homolog 2) is a molybdoflavoenzyme. Harderian glands are the richest source of AOH2, although the protein is detectable also in sebaceous glands, epidermis, and other keratinized epithelia. The levels of AOH2 in the Harderian gland and skin are controlled by genetic background, being maximal in CD1 and C57BL/6 and minimal in DBA/2, CBA, and 129/Sv strains. Testosterone is a negative regulator of AOH2 in Harderian glands. Purified AOH2 oxidizes retinaldehyde into retinoic acid, while it is devoid of pyridoxal-oxidizing activity. Aoh2(-/-) mice, the first aldehyde oxidase knockout animals ever generated, are viable and fertile. The data obtained for this knockout model indicate a significant role of AOH2 in the local synthesis and biodisposition of endogenous retinoids in the Harderian gland and skin. The Harderian gland's transcriptome of knockout mice demonstrates overall downregulation of direct retinoid-dependent genes as well as perturbations in pathways controlling lipid homeostasis and cellular secretion, particularly in sexually immature animals. The skin of knockout mice is characterized by thickening of the epidermis in basal conditions and after UV light exposure. This has correlates in the corresponding transcriptome, which shows enrichment and overall upregulation of genes involved in hypertrophic responses.
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Mendel RR, Bittner F. Cell biology of molybdenum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:621-35. [PMID: 16784786 DOI: 10.1016/j.bbamcr.2006.03.013] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/13/2006] [Accepted: 03/18/2006] [Indexed: 11/17/2022]
Abstract
The transition element molybdenum (Mo) is of essential importance for (nearly) all biological systems as it is required by enzymes catalyzing diverse key reactions in the global carbon, sulfur and nitrogen metabolism. The metal itself is biologically inactive unless it is complexed by a special cofactor. With the exception of bacterial nitrogenase, where Mo is a constituent of the FeMo-cofactor, Mo is bound to a pterin, thus forming the molybdenum cofactor (Moco) which is the active compound at the catalytic site of all other Mo-enzymes. In eukaryotes, the most prominent Mo-enzymes are (1) sulfite oxidase, which catalyzes the final step in the degradation of sulfur-containing amino acids and is involved in detoxifying excess sulfite, (2) xanthine dehydrogenase, which is involved in purine catabolism and reactive oxygen production, (3) aldehyde oxidase, which oxidizes a variety of aldehydes and is essential for the biosynthesis of the phytohormone abscisic acid, and in autotrophic organisms also (4) nitrate reductase, which catalyzes the key step in inorganic nitrogen assimilation. All Mo-enzymes, except plant sulfite oxidase, need at least one more redox active center, many of them involving iron in electron transfer. The biosynthesis of Moco involves the complex interaction of six proteins and is a process of four steps, which also includes iron as well as copper in an indispensable way. Moco as released after synthesis is likely to be distributed to the apoproteins of Mo-enzymes by putative Moco-carrier proteins. Xanthine dehydrogenase and aldehyde oxidase, but not sulfite oxidase and nitrate reductase, require the post-translational sulfuration of their Mo-site for becoming active. This final maturation step is catalyzed by a Moco-sulfurase enzyme, which mobilizes sulfur from l-cysteine in a pyridoxal phosphate-dependent manner as typical for cysteine desulfurases.
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Affiliation(s)
- Ralf R Mendel
- Department of Plant Biology, Technical University of Braunschweig, Humboldtstrasse 1, 38106 Braunschweig, Germany.
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Terao M, Kurosaki M, Barzago MM, Varasano E, Boldetti A, Bastone A, Fratelli M, Garattini E. Avian and Canine Aldehyde Oxidases. J Biol Chem 2006; 281:19748-61. [PMID: 16672219 DOI: 10.1074/jbc.m600850200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aldehyde oxidases are molybdo-flavoenzymes structurally related to xanthine oxidoreductase. They catalyze the oxidation of aldehydes or N-heterocycles of physiological, pharmacological, and toxicological relevance. Rodents are characterized by four aldehyde oxidases as follows: AOX1 and aldehyde oxidase homologs 1-3 (AOH1, AOH2, and AOH3). Humans synthesize a single functional aldehyde oxidase, AOX1. Here we define the structure and the characteristics of the aldehyde oxidase genes and proteins in chicken and dog. The avian genome contains two aldehyde oxidase genes, AOX1 and AOH, mapping to chromosome 7. AOX1 and AOH are structurally very similar and code for proteins whose sequence was deduced from the corresponding cDNAs. AOX1 is the ortholog of the same gene in mammals, whereas AOH represents the likely ancestor of rodent AOH1, AOH2, and AOH3. The dog genome is endowed with two structurally conserved and active aldehyde oxidases clustering on chromosome 37. Cloning of the corresponding cDNAs and tissue distribution studies demonstrate that they are the orthologs of rodent AOH2 and AOH3. The vestiges of dog AOX1 and AOH1 are recognizable upstream of AOH2 and AOH3 on the same chromosome. Comparison of the complement and the structure of the aldehyde oxidase and xanthine oxidoreductase genes in vertebrates and other animal species indicates that they evolved through a series of duplication and inactivation events. Purification of the chicken AOX1 protein to homogeneity from kidney demonstrates that the enzyme possesses retinaldehyde oxidase activity. Unlike humans and most other mammals, dog and chicken are devoid of liver aldehyde oxidase activity.
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Affiliation(s)
- Mineko Terao
- Laboratory of Molecular Biology, Centro Catullo e Daniela Borgomainerio, Istituto di Ricerche Farmacologiche Mario Negri, via Eritrea 62, 20157 Milano, Italy
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Seo Y, Yan T, Schupp JE, Radivoyevitch T, Kinsella TJ. Schedule-dependent drug effects of oral 5-iodo-2-pyrimidinone-2'-deoxyribose as an in vivo radiosensitizer in U251 human glioblastoma xenografts. Clin Cancer Res 2006; 11:7499-507. [PMID: 16243824 DOI: 10.1158/1078-0432.ccr-05-1138] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE 5-Iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is an oral prodrug of 5-iodo-2'-deoxyuridine (IUdR), an in vitro/in vivo radiosensitizer. IPdR can be rapidly converted to IUdR by a hepatic aldehyde oxidase. Previously, we found that the enzymatic conversion of IPdR to IUdR could be transiently reduced using a once daily (q.d.) treatment schedule and this may affect IPdR-mediated tumor radiosensitization. The purpose of this study is to measure the effect of different drug dosing schedules on tumor radiosensitization and therapeutic index in human glioblastoma xenografts. EXPERIMENTAL DESIGN Three different IPdR treatment schedules (thrice a day, t.i.d.; every other day, q.o.d.; every 3rd day, q.3.d.), compared with a q.d. schedule, were analyzed using athymic nude mice with human glioblastoma (U251) s.c. xenografts. Plasma pharmacokinetics, IUdR-DNA incorporation in tumor and normal proliferating tissues, tumor growth delay following irradiation, and body weight loss were used as end points. RESULTS The t.i.d. schedule with the same total daily doses as the q.d. schedule (250, 500, or 1,000 mg/kg/d) improved the efficiency of IPdR conversion to IUdR. As a result, the percentage of IUdR-DNA incorporation was higher using the t.i.d. schedule in the tumor xenografts as well as in normal small intestine and bone marrow. Using a fixed dose (500 mg/kg) per administration, the q.o.d. and q.3.d. schedules also showed greater IPdR conversion than the q.d. schedule, related to a greater recovery of hepatic aldehyde oxidase activity prior to the next drug dosing. In the tumor regrowth assay, all IPdR treatment schedules showed significant increases of regrowth delays compared with the control without IPdR (q.o.d., 29.4 days; q.d., 29.7 days; t.i.d., 34.7 days; radiotherapy alone, 15.7 days). The t.i.d. schedule also showed a significantly enhanced tumor growth delay compared with the q.d. schedule. Additionally, the q.o.d. schedule resulted in a significant reduction in systemic toxicity. CONCLUSIONS The t.i.d. and q.o.d. dosing schedules improved the efficiency of enzymatic activation of IPdR to IUdR during treatment and changed the extent of tumor radiosensitization and/or systemic toxicity compared with a q.d. dosing schedule. These dosing schedules will be considered for future clinical trials of IPdR-mediated human tumor radiosensitization.
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Affiliation(s)
- Yuji Seo
- Department of Radiation Oncology and Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, Ohio 44106-6068, USA
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Rivera SP, Choi HH, Chapman B, Whitekus MJ, Terao M, Garattini E, Hankinson O. Identification of aldehyde oxidase 1 and aldehyde oxidase homologue 1 as dioxin-inducible genes. Toxicology 2005; 207:401-9. [PMID: 15664268 DOI: 10.1016/j.tox.2004.10.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Revised: 10/04/2004] [Accepted: 10/24/2004] [Indexed: 10/26/2022]
Abstract
Aldehyde oxidases are a family of highly related molybdo-flavoenzymes acting upon a variety of compounds of industrial and medical importance. We have identified aldehyde oxidase 1 (AOX1) as a 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) inducible gene in the mouse hepatoma cell line Hepa-1. AOX1 mRNA levels were not increased by dioxin in mutant derivatives of the Hepa-1 cell line lacking either functional aryl hydrocarbon receptor (AHR) or aryl hydrocarbon receptor nuclear translocator (ARNT) proteins, thus demonstrating that transcriptional induction of AOX1 in response to dioxin occurs through the AHR pathway. Dioxin induction of AOX1 mRNA was also observed in mouse liver. In addition, levels of AOX1 protein as well as those of aldehyde oxidase homologue 1 (AOH1), a recently identified homolog of AOX1, were elevated in mouse liver in response to dioxin. Employing an aldehyde oxidase specific substrate, AOX1/AOH1 activity was shown to be induced by dioxin in mouse liver. This activity was inhibited by a known inhibitor of aldehyde oxidases, and eliminated by including tungstate in the mouse diet, which is known to lead to inactivation of molybdoflavoenzymes, thus confirming that the enzymatic activity was attributable to AOX1/AOH1. Our observations thus identify two additional xenobiotic metabolizing enzymes induced by dioxin.
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MESH Headings
- Aldehyde Oxidoreductases/antagonists & inhibitors
- Aldehyde Oxidoreductases/biosynthesis
- Aldehyde Oxidoreductases/genetics
- Animals
- Aryl Hydrocarbon Receptor Nuclear Translocator
- Carcinoma, Hepatocellular/enzymology
- Carcinoma, Hepatocellular/genetics
- Cell Line, Tumor
- DNA-Binding Proteins/deficiency
- DNA-Binding Proteins/genetics
- Diet
- Drug Therapy, Combination
- Environmental Pollutants/administration & dosage
- Environmental Pollutants/toxicity
- Enzyme Induction
- Enzyme Inhibitors/administration & dosage
- Gene Expression Regulation, Enzymologic/drug effects
- Injections, Intraperitoneal
- Liver/drug effects
- Liver/enzymology
- Mice
- Mice, Inbred C57BL
- Mitochondrial Proteins
- Oxidoreductases/antagonists & inhibitors
- Oxidoreductases/biosynthesis
- Oxidoreductases/genetics
- Plant Proteins
- Polychlorinated Dibenzodioxins/administration & dosage
- Polychlorinated Dibenzodioxins/toxicity
- RNA, Messenger/metabolism
- Receptors, Aryl Hydrocarbon/deficiency
- Receptors, Aryl Hydrocarbon/genetics
- Transcription Factors/deficiency
- Transcription Factors/genetics
- Tungsten Compounds/administration & dosage
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Affiliation(s)
- Steven P Rivera
- Department of Pathology and Laboratory Medicine, Jonsson Comprehensive Cancer Center, University of California, 650 Charles E. Young Dr., Factor Bldg. 13-230, Los Angeles, CA 90095-1732, USA
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Kurosaki M, Terao M, Barzago MM, Bastone A, Bernardinello D, Salmona M, Garattini E. The aldehyde oxidase gene cluster in mice and rats. Aldehyde oxidase homologue 3, a novel member of the molybdo-flavoenzyme family with selective expression in the olfactory mucosa. J Biol Chem 2004; 279:50482-98. [PMID: 15383531 DOI: 10.1074/jbc.m408734200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian molybdo-flavoenzymes are oxidases requiring FAD and molybdopterin (molybdenum cofactor) for their catalytic activity. This family of proteins was thought to consist of four members, xanthine oxidoreductase, aldehyde oxidase 1 (AOX1), and the aldehyde oxidase homologues 1 and 2 (AOH1 and AOH2, respectively). Whereas the first two enzymes are present in humans and various other mammalian species, the last two proteins have been described only in mice. Here, we report on the identification, in both mice and rats, of a novel molybdo-flavoenzyme, AOH3. In addition, we have cloned the cDNAs coding for rat AOH1 and AOH2, demonstrating that this animal species has the same complement of molybdo-flavoproteins as the mouse. The AOH3 cDNA is characterized by remarkable similarity to AOX1, AOH1, AOH2, and xanthine oxidoreductase cDNAs. Mouse AOH3 is selectively expressed in Bowman's glands of the olfactory mucosa, although small amounts of the corresponding mRNA are present also in the skin. In the former location, two alternatively spliced forms of the AOH3 transcript with different 3'-untranslated regions were identified. The general properties of AOH3 were determined by purification of mouse AOH3 from the olfactory mucosa. The enzyme possesses aldehyde oxidase activity and oxidizes, albeit with low efficiency, exogenous substrates that are recognized by AOH1 and AOX1. The Aoh3 gene maps to mouse chromosome 1 band c1 and rat chromosome 7 in close proximity to the Aox1, Aoh1, and Aoh2 loci and has an exon/intron structure almost identical to that of the other molybdo-flavoenzyme genes in the two species.
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Affiliation(s)
- Mami Kurosaki
- Laboratory of Molecular Biology, Centro Catullo e Daniela Borgomainerio, Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy
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Vila R, Kurosaki M, Barzago MM, Kolek M, Bastone A, Colombo L, Salmona M, Terao M, Garattini E. Regulation and biochemistry of mouse molybdo-flavoenzymes. The DBA/2 mouse is selectively deficient in the expression of aldehyde oxidase homologues 1 and 2 and represents a unique source for the purification and characterization of aldehyde oxidase. J Biol Chem 2003; 279:8668-83. [PMID: 14665639 DOI: 10.1074/jbc.m308137200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mouse molybdo-flavoenzymes consist of xanthine oxidoreductase, aldehyde oxidase (AOX1), and two recently identified proteins, AOH1 and AOH2 (aldehyde oxidase homologues 1 and 2). Here we demonstrate that CD-1, C57BL/6, 129/Sv, and other mouse strains synthesize high levels of AOH1 in the liver and AOH2 in the skin. By contrast, the DBA/2 and CBA strains are unique, having a selective deficit in the expression of the AOH1 and AOH2 genes. DBA/2 animals synthesize trace amounts of a catalytically active AOH1 protein. However, relative to CD-1 animals, an over 2 log reduction in the steady-state levels of liver AOH1 mRNA, protein, and enzymatic activity is observed in basal conditions and following administration of testosterone. The DBA/2 mouse represents a unique opportunity to purify AOX1 and compare its enzymatic characteristics to those of the AOH1 protein. The spectroscopy and biochemistry of AOX1 are very similar to those of AOH1 except for a differential sensitivity to the non-competitive inhibitory effect of norharmane. AOX1 and AOH1 oxidize an overlapping set of aldehydes and heterocycles. For most compounds, the substrate efficiency (V(max)/K(m)) of AOX1 is superior to that of AOH1. Alkylic alcohols and acetaldehyde, the toxic metabolite of ethanol, are poor substrates of both enzymes. Consistent with this, the levels of acetaldehyde in the livers of ethanol administered CD-1 and DBA/2 mice are similar, indicating that neither enzyme is involved in the in vivo biotransformation of acetaldehyde.
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Affiliation(s)
- Ruth Vila
- Department of Biochemistry and Molecular Pharmacology, Istituto di Ricerche Farmacologiche, "Mario Negri," via Eritrea, 62, Milano 20157, Italy
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Garattini E, Mendel R, Romão MJ, Wright R, Terao M. Mammalian molybdo-flavoenzymes, an expanding family of proteins: structure, genetics, regulation, function and pathophysiology. Biochem J 2003; 372:15-32. [PMID: 12578558 PMCID: PMC1223366 DOI: 10.1042/bj20030121] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2003] [Revised: 02/04/2003] [Accepted: 02/10/2003] [Indexed: 12/11/2022]
Abstract
The molybdo-flavoenzymes are structurally related proteins that require a molybdopterin cofactor and FAD for their catalytic activity. In mammals, four enzymes are known: xanthine oxidoreductase, aldehyde oxidase and two recently described mouse proteins known as aldehyde oxidase homologue 1 and aldehyde oxidase homologue 2. The present review article summarizes current knowledge on the structure, enzymology, genetics, regulation and pathophysiology of mammalian molybdo-flavoenzymes. Molybdo-flavoenzymes are structurally complex oxidoreductases with an equally complex mechanism of catalysis. Our knowledge has greatly increased due to the recent crystallization of two xanthine oxidoreductases and the determination of the amino acid sequences of many members of the family. The evolution of molybdo-flavoenzymes can now be traced, given the availability of the structures of the corresponding genes in many organisms. The genes coding for molybdo-flavoenzymes are expressed in a cell-specific fashion and are controlled by endogenous and exogenous stimuli. The recent cloning of the genes involved in the biosynthesis of the molybdenum cofactor has increased our knowledge on the assembly of the apo-forms of molybdo-flavoproteins into the corresponding holo-forms. Xanthine oxidoreductase is the key enzyme in the catabolism of purines, although recent data suggest that the physiological function of this enzyme is more complex than previously assumed. The enzyme has been implicated in such diverse pathological situations as organ ischaemia, inflammation and infection. At present, very little is known about the pathophysiological relevance of aldehyde oxidase, aldehyde oxidase homologue 1 and aldehyde oxidase homologue 2, which do not as yet have an accepted endogenous substrate.
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Affiliation(s)
- Enrico Garattini
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche Mario Negri, via Eritrea 62, 20157 Milan, Italy.
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