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Pimviriyakul P, Sucharitakul J, Maenpuen S. Mechanistic insights into iron-sulfur clusters and flavin oxidation of a novel xanthine oxidoreductase from Sulfobacillus acidophilus TPY. FEBS J 2024; 291:527-546. [PMID: 37899720 DOI: 10.1111/febs.16987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 10/04/2023] [Accepted: 10/24/2023] [Indexed: 10/31/2023]
Abstract
Xanthine oxidoreductase (XOR) catalyzes the oxidation of purines (hypoxanthine and xanthine) to uric acid. XOR is widely used in various therapeutic and biotechnological applications. In this study, we characterized the biophysical and mechanistic properties of a novel bacterial XOR from Sulfobacillus acidophilus TPY (SaXOR). Our results showed that SaXOR is a heterotrimer consisting of three subunits, namely XoA, XoB, and XoC, which denote the molybdenum cofactor (Moco), 2Fe-2S, and FAD-binding domains, respectively. XoC was found to be stable when co-expressed with XoB, forming an XoBC complex. Furthermore, we prepared a fusion of XoB and XoC via a flexible linker (fusXoBC) and evaluated its function in comparison to that of XoBC. Spectroscopic analysis revealed that XoB harbors two 2Fe-2S clusters, whereas XoC bears a single-bound FAD cofactor. Electron transfer from reduced forms of XoC, XoBC, and fusXoBC to molecular oxygen (O2 ) during oxidative half-reaction yielded no flavin semiquinones, implying ultrafast single-electron transfer from 2Fe-2Sred to FAD. In the presence of XoA, XoBC and fusXoBC exhibited comparable XoA affinity and exploited a shared overall mechanism. Nonetheless, the linkage may accelerate the two-step, single-electron transfer cascade from 2Fe-2Sred to FAD while augmenting protein stability. Collectively, our findings provide novel insights into SaXOR properties and oxidation mechanisms divergent from prior mammalian and bacterial XOR paradigms.
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Affiliation(s)
- Panu Pimviriyakul
- Department of Biochemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Jeerus Sucharitakul
- Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
- Skeletal Disorders Research Unit, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Somchart Maenpuen
- Department of Biochemistry, Faculty of Science, Burapha University, Chonburi, Thailand
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Wang C, Zhang R, Sun Y, Wen Y, Liu X, Xing X. Combinatorial co-expression of xanthine dehydrogenase and chaperone XdhC from Acinetobacter baumannii and Rhodobacter capsulatus and their applications in decreasing purine content in food. FOOD SCIENCE AND HUMAN WELLNESS 2023. [DOI: 10.1016/j.fshw.2022.10.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Functional mononuclear molybdenum enzymes: challenges and triumphs in molecular cloning, expression, and isolation. J Biol Inorg Chem 2020; 25:547-569. [PMID: 32279136 DOI: 10.1007/s00775-020-01787-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 03/30/2020] [Indexed: 10/24/2022]
Abstract
Mononuclear molybdenum enzymes catalyze a variety of reactions that are essential in the cycling of nitrogen, carbon, arsenic, and sulfur. For decades, the structure and function of these crucial enzymes have been investigated to develop a fundamental knowledge for this vast family of enzymes and the chemistries they carry out. Therefore, obtaining abundant quantities of active enzyme is necessary for exploring this family's biochemical capability. This mini-review summarizes the methods for overexpressing mononuclear molybdenum enzymes in the context of the challenges encountered in the process. Effective methods for molybdenum cofactor synthesis and incorporation, optimization of expression conditions, improving isolation of active vs. inactive enzyme, incorporation of additional prosthetic groups, and inclusion of redox enzyme maturation protein chaperones are discussed in relation to the current molybdenum enzyme literature. This article summarizes the heterologous and homologous expression studies providing underlying patterns and potential future directions.
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Abstract
The transition element molybdenum (Mo) is of primordial importance for biological systems as it is required by enzymes catalyzing key reactions in global carbon, sulfur, and nitrogen metabolism. In order to gain biological activity, Mo has to be complexed by a special cofactor. With the exception of bacterial nitrogenase, all Mo-dependent enzymes contain a unique pyranopterin-based cofactor coordinating a Mo atom at their catalytic site. Various types of reactions are catalyzed by Mo enzymes in prokaryotes, including oxygen atom transfer, sulfur or proton transfer, hydroxylation, or even nonredox ones. Mo enzymes are widespread in prokaryotes, and many of them were likely present in LUCA. To date, more than 50-mostly bacterial-Mo enzymes are described in nature. In a few eubacteria and in many archaea, Mo is replaced by tungsten bound to the same unique pyranopterin. How Moco is synthesized in bacteria is reviewed as well as the way until its insertion into apo-Mo-enzymes.
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Jiang Y, Tang H, Wu G, Xu P. Functional Identification of a Novel Gene, moaE, for 3-Succinoylpyridine Degradation in Pseudomonas putida S16. Sci Rep 2015; 5:13464. [PMID: 26304596 PMCID: PMC4548258 DOI: 10.1038/srep13464] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/28/2015] [Indexed: 12/01/2022] Open
Abstract
Microbial degradation of N-heterocyclic compounds, including xanthine, quinoline, nicotinate, and nicotine, frequently requires molybdenum hydroxylases. The intramolecular electron transfer chain of molybdenum hydroxylases consists of a molybdenum cofactor, two distinct [2Fe-2S] clusters, and flavin adenine dinucleotide. 3-Succinoylpyridine monooxygenase (Spm), responsible for the transformation from 3-succinoylpyridine to 6-hydroxy-3-succinoylpyridine, is a crucial enzyme in the pyrrolidine pathway of nicotine degradation in Pseudomonas. Our previous work revealed that the heterotrimeric enzyme (SpmA, SpmB, and SpmC) requires molybdopterin cytosine dinucleotide as a cofactor for their activities. In this study, we knocked out four genes, including PPS_1556, PPS_2936, PPS_4063, and PPS_4397, and found that a novel gene, PPS_4397 encoding moaE, is necessary for molybdopterin cytosine dinucleotide biosynthesis. Resting cell reactions of the moaE deletion mutant incubated with 3 g l−1 nicotine at 30 °C resulted in accumulation of 3-succinoylpyridine, and the strain complemented by the moaE gene regained the ability to convert 3-succinoylpyridine. In addition, reverse transcription-quantitative polymerase chain reaction analysis indicated that the transcriptional levels of the genes of moaE, spmA, and spmC of Pseudomonas putida S16 were distinctly higher when grown in nicotine medium than in glycerol medium.
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Affiliation(s)
- Yi Jiang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.,Joint International Research Laboratory of Metabolic &Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Hongzhi Tang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.,Joint International Research Laboratory of Metabolic &Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Geng Wu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.,Joint International Research Laboratory of Metabolic &Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Ping Xu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.,Joint International Research Laboratory of Metabolic &Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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Ütkür FO, Thanh Tran T, Collins J, Brandenbusch C, Sadowski G, Schmid A, Bühler B. Integrated organic-aqueous biocatalysis and product recovery for quinaldine hydroxylation catalyzed by living recombinant Pseudomonas putida. J Ind Microbiol Biotechnol 2012; 39:1049-59. [PMID: 22383177 DOI: 10.1007/s10295-012-1106-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 02/07/2012] [Indexed: 11/29/2022]
Abstract
In an earlier study, biocatalytic carbon oxyfunctionalization with water serving as oxygen donor, e.g., the bioconversion of quinaldine to 4-hydroxyquinaldine, was successfully achieved using resting cells of recombinant Pseudomonas putida, containing the molybdenum-enzyme quinaldine 4-oxidase, in a two-liquid phase (2LP) system (Ütkür et al. J Ind Microbiol Biotechnol 38:1067-1077, 2011). In the study reported here, key parameters determining process performance were investigated and an efficient and easy method for product recovery was established. The performance of the whole-cell biocatalyst was shown not to be limited by the availability of the inducer benzoate (also serving as growth substrate) during the growth of recombinant P. putida cells. Furthermore, catalyst performance during 2LP biotransformations was not limited by the availability of glucose, the energy source to maintain metabolic activity in resting cells, and molecular oxygen, a possible final electron acceptor during quinaldine oxidation. The product and the organic solvent (1-dodecanol) were identified as the most critical factors affecting biocatalyst performance, to a large extent on the enzyme level (inhibition), whereas substrate effects were negligible. However, none of the 13 alternative solvents tested surpassed 1-dodecanol in terms of toxicity, substrate/product solubility, and partitioning. The use of supercritical carbon dioxide for phase separation and an easy and efficient liquid-liquid extraction step enabled 4-hydroxyquinaldine to be isolated at a purity of >99.9% with recoveries of 57 and 84%, respectively. This study constitutes the first proof of concept on an integrated process for the oxyfunctionalization of toxic substrates with a water-incorporating hydroxylase.
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Affiliation(s)
- F Ozde Ütkür
- Laboratory of Chemical Biotechnology, Department of Biochemical and Chemical Engineering, TU Dortmund University, Emil-Figge-Str. 66, 44227, Dortmund, Germany
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Mendel RR, Kruse T. Cell biology of molybdenum in plants and humans. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1568-79. [PMID: 22370186 DOI: 10.1016/j.bbamcr.2012.02.007] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 02/08/2012] [Accepted: 02/10/2012] [Indexed: 12/29/2022]
Abstract
The transition element molybdenum (Mo) needs to be complexed by a special cofactor in order to gain catalytic activity. With the exception of bacterial Mo-nitrogenase, where Mo is a constituent of the FeMo-cofactor, Mo is bound to a pterin, thus forming the molybdenum cofactor Moco, which in different variants is the active compound at the catalytic site of all other Mo-containing enzymes. In eukaryotes, 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 requires iron, ATP and copper. After its synthesis, Moco is distributed to the apoproteins of Mo-enzymes by Moco-carrier/binding proteins. A deficiency in the biosynthesis of Moco has lethal consequences for the respective organisms. In humans, Moco deficiency is a severe inherited inborn error in metabolism resulting in severe neurodegeneration in newborns and causing early childhood death. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Ralf R Mendel
- Institute of Plant Biology, Braunschweig University of Technology, 1 Humboldt Street, 38106 Braunschweig, Germany.
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The role of system-specific molecular chaperones in the maturation of molybdoenzymes in bacteria. Biochem Res Int 2010; 2011:850924. [PMID: 21151514 PMCID: PMC2997495 DOI: 10.1155/2011/850924] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 08/31/2010] [Indexed: 11/18/2022] Open
Abstract
Biogenesis of prokaryotic molybdoenzymes is a complex process with the final step representing the insertion of a matured molybdenum cofactor (Moco) into a folded apoenzyme. Usually, specific chaperones of the XdhC family are required for the maturation of molybdoenzymes of the xanthine oxidase family in bacteria. Enzymes of the xanthine oxidase family are characterized to contain an equatorial sulfur ligand at the molybdenum center of Moco. This sulfur ligand is inserted into Moco while bound to the XdhC-like protein and before its insertion into the target enzyme. In addition, enzymes of the xanthine oxidase family bind either the molybdopterin (Mo-MPT) form of Moco or the modified molybdopterin cytosine dinucleotide cofactor (MCD). In both cases, only the matured cofactor is inserted by a proofreading process of XdhC. The roles of these specific XdhC-like chaperones during the biogenesis of enzymes of the xanthine oxidase family in bacteria are described.
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Wollers S, Heidenreich T, Zarepour M, Zachmann D, Kraft C, Zhao Y, Mendel RR, Bittner F. Binding of Sulfurated Molybdenum Cofactor to the C-terminal Domain of ABA3 from Arabidopsis thaliana Provides Insight into the Mechanism of Molybdenum Cofactor Sulfuration. J Biol Chem 2008; 283:9642-50. [DOI: 10.1074/jbc.m708549200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Gao Q, Thorson JS. The biosynthetic genes encoding for the production of the dynemicin enediyne core in Micromonospora chersina ATCC53710. FEMS Microbiol Lett 2008; 282:105-14. [PMID: 18328078 DOI: 10.1111/j.1574-6968.2008.01112.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Dynemicin is a novel anthraquinone-fused member of the 10-membered enediyne antitumor antibiotic family. The development of a genetic system for the dynemicin producer Micromonospora chersina confirmed, for the first time, the requirement of the putative enediyne core biosynthetic genes (dynE8, U14 and U15) and a tailoring oxidase gene (orf23) for dynemicin production. Cloning and sequence analysis of a 76 kb of genomic sequence region containing dynE8 revealed a variety of genes conserved among known enediyne loci. Surprisingly, this fragment and flanking chromosomal DNA lacked any obvious genes encoding for the biosynthesis of the anthraquinone, suggesting that the location of genes encoding for the biosynthesis of the dynemicin enediyne core and the dynemicin anthraquinone are chromosomally distinct. The demonstrated trace production of a shunt product from mutant strain QGD23 (Deltaorf23) also sets the stage for subsequent studies to delineate the key steps in enediyne core biosynthesis and tailoring.
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Affiliation(s)
- Qunjie Gao
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705, USA
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Sachelaru P, Schiltz E, Brandsch R. A functional mobA gene for molybdopterin cytosine dinucleotide cofactor biosynthesis is required for activity and holoenzyme assembly of the heterotrimeric nicotine dehydrogenases of Arthrobacter nicotinovorans. Appl Environ Microbiol 2006; 72:5126-31. [PMID: 16820521 PMCID: PMC1489357 DOI: 10.1128/aem.00437-06] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two Arthrobacter nicotinovorans molybdenum enzymes hydroxylate the pyridine ring of nicotine. Molybdopterin cytosine dinucleotide (MCD) was determined to be a cofactor of these enzymes. A mobA gene responsible for the formation of MCD could be identified and its function shown to be required for assembly of the heterotrimeric molybdenum enzymes.
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Affiliation(s)
- Paula Sachelaru
- Institute for Biochemistry and Molecular Biology, University of Freiburg, Hermann-Herder-Strasse 7, 79104 Freiburg, Germany
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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: 176] [Impact Index Per Article: 9.8] [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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Neumann M, Schulte M, Jünemann N, Stöcklein W, Leimkühler S. Rhodobacter capsulatus XdhC Is Involved in Molybdenum Cofactor Binding and Insertion into Xanthine Dehydrogenase. J Biol Chem 2006; 281:15701-8. [PMID: 16597619 DOI: 10.1074/jbc.m601617200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhodobacter capsulatus xanthine dehydrogenase (XDH) is a cytoplasmic enzyme with an (alphabeta)2 heterodimeric structure that is highly identical to homodimeric eukaryotic xanthine oxidoreductases. The crystal structure revealed that the molybdenum cofactor (Moco) is deeply buried within the protein. A protein involved in Moco insertion and XDH maturation has been identified, which was designated XdhC. XdhC was shown to be essential for the production of active XDH but is not a subunit of the purified enzyme. Here we describe the purification of XdhC and the detailed characterization of its role for XDH maturation. We could show that XdhC binds Moco in stoichiometric amounts, which subsequently can be inserted into Moco-free apo-XDH. A specific interaction between XdhC and XdhB was identified. We show that XdhC is required for the stabilization of the sulfurated form of Moco present in enzymes of the xanthine oxidase family. Our findings imply that enzyme-specific proteins exist for the biogenesis of molybdoenzymes, coordinating Moco binding and insertion into their respective target proteins. So far, the requirement of such proteins for molybdoenzyme maturation has been described only for prokaryotes.
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Affiliation(s)
- Meina Neumann
- Department of Proteinanalytics, Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany
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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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Ivanov NV, Trani M, Edmondson DE. High-level expression and characterization of a highly functional Comamonas acidovorans xanthine dehydrogenase in Pseudomonas aeruginosa. Protein Expr Purif 2004; 37:72-82. [PMID: 15294283 DOI: 10.1016/j.pep.2004.05.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2004] [Revised: 03/22/2004] [Indexed: 10/26/2022]
Abstract
An improved procedure is described for the high-level expression of Comamonas acidovorans XDH in Pseudomonas aeruginosa PAO1-LAC. The level of functional expression (56 mg protein/L culture) is found to be 7-fold higher than that observed in Escherichia coli and 30-fold higher than that induced in C. acidovorans. Co-expression of the xdhC gene is required for maximal level of functional expression. Comparison of purified preparations of XDH expressed in the absence of xdhC (XDH(AB)) with that expressed in its presence (XDH(ABC)) shows the increased level of activity due to the level of Mo incorporation. The Fe and FAD contents of expressed enzymes are independent of xdhC co-expression. Electron paramagnetic resonance spectroscopy, circular dichroism spectroscopy, metal analysis, and kinetic properties of recombinant purified XDH(ABC) are identical with those exhibited by the native enzyme. This expression system should serve as a valuable tool for further biophysical and mechanistic investigations of xanthine dehydrogenase by site-directed mutagenesis. A method is also described to evaluate the suitability of P. aeruginosa and other organisms as potential expression hosts for five different sources of xdh genes.
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