1
|
Suzuki H. Remarkable diversification of bacterial azoreductases: primary sequences, structures, substrates, physiological roles, and biotechnological applications. Appl Microbiol Biotechnol 2019; 103:3965-3978. [PMID: 30941462 DOI: 10.1007/s00253-019-09775-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/13/2019] [Accepted: 03/15/2019] [Indexed: 12/12/2022]
Abstract
Azoreductases reductively cleave azo linkages by using NAD(P)H as an electron donor. The enzymes are widely found in bacteria and act on numerous azo dyes, which allow various unique applications. This review describes primary amino acid sequences, structures, substrates, physiological roles, and biotechnological applications of bacterial azoreductases to discuss their remarkable diversification. According to primary sequences, azoreductases were classified phylogenetically into four main clades. Most members of clades I-III are flavoproteins, whereas clade IV members include flavin-free azoreductases. Clades I and II prefer NADPH and NADH, respectively, as electron donors, whereas other members generally use both. Several enzymes formed no clades; moreover, some bacteria produce azoreductases with longer primary structures than those hitherto identified, which implies further diversification of bacterial azoreductases. The crystal structures commonly reveal the Rossmann folds; however, ternary structures are moderately varied with different quaternary conformation. Although physiological roles are obscure, several azoreductases have been shown to act on metabolites such as flavins, quinones, and metal ions more efficiently than on azo dyes. Considering that many homologs exclusively act on these metabolites, it is possible that azoreductases are actually side activities of versatile reductases that act on various substrates with different specificities. In parallel, this idea raises the possibility that homologous enzymes, even if these are already defined as other types of reductases, widely harbor azoreductase activities. Although azoreductases for which their genes have been identified are not abundant, it may be simple to identify azoreductases of biotechnological importance that have novel substrate specificities.
Collapse
Affiliation(s)
- Hirokazu Suzuki
- Faculty of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8552, Japan. .,Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8552, Japan.
| |
Collapse
|
2
|
Nakhaee N, Asad S, Khajeh K, Arab SS, Amoozegar MA. Improving the thermal stability of azoreductase from Halomonas elongata by introducing a disulfide bond via site-directed mutagenesis. Biotechnol Appl Biochem 2018; 65:883-891. [PMID: 30132989 DOI: 10.1002/bab.1688] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/11/2018] [Indexed: 11/06/2022]
Abstract
Azoreductases mainly reduce azo dyes, the largest class of colorants, to colorless aromatic amines. AzoH, a new azoreductase from the halophilic bacterium, Halomonas elongata, has been recently cloned and expressed in Escherichia coli. The aim of this study was to improve thermal stability of this enzyme by introducing new disulfide bonds. Since X-ray crystallography was not available, homology modeling and molecular dynamics was used to construct the enzyme three-dimensional structure. Potential disulfide bonds for increasing thermal stability were found using DIScover online software. Appropriate mutations (L49C/D108C) to form a disulfide bond were introduced by the Quik-Change method. Mutant protein expressed in E. coli showed increased thermal stability at 50 °C (increased half-life from 12.6 Min in AzoH to 26.66 Min in a mutated enzyme). The mutated enzyme could also tolerate 5% (w/v) NaCl and retained 30% of original activity after 24 H incubation, whereas the wild-type enzyme was completely inactivated. According to circular dichroism studies, the secondary structure was not altered by this mutation; however, a blue shift in intrinsic florescent graph revealed changes in the tertiary structure. This is the first study to improve thermal stability and salt tolerance of a halophilic azoreductase.
Collapse
Affiliation(s)
- Narjes Nakhaee
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | - Sedigheh Asad
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | - Khosro Khajeh
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Seyed Shahriar Arab
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mohammad Ali Amoozegar
- Extremophiles Laboratory, Department of Microbiology, School of Biology and Center of Excellence in Phylogeny of Living Organisms, College of Science, University of Tehran, Tehran, Iran
| |
Collapse
|
3
|
Millerick KA, Johnston JT, Finneran KT. Photobiological transformation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using Rhodobacter sphaeroides. CHEMOSPHERE 2016; 159:138-144. [PMID: 27285383 DOI: 10.1016/j.chemosphere.2016.05.056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/15/2016] [Accepted: 05/18/2016] [Indexed: 06/06/2023]
Abstract
Pump-and-treat strategies for groundwater containing explosives may be necessary when the contaminated water approaches sensitive receptors. This project investigated bacterial photosynthesis as a strategy for ex situ treatment, using light as the primary energy source to facilitate RDX transformation. The objective was to characterize the ability of photosynthetic Rhodobacter sphaeroides (strain ATCC(®) 17023 ™) to transform the high-energy explosive RDX. R. sphaeroides transformed 30 μM RDX within 40 h under light conditions; RDX was not fully transformed in the dark (non-photosynthetic conditions), suggesting that photosynthetic electron transfer was the primary mechanism. Experiments with RDX demonstrated that succinate and malate were the most effective electron donors for photosynthesis, but glycerol was also utilized as a photosynthetic electron donor. RDX was transformed irrespective of the presence of carbon dioxide. The electron shuttling compound anthraquinone-2,6-disulfonate (AQDS) increased transformation kinetics in the absence of CO2, when the cells had excess NADPH that needed to be re-oxidized because there was limited CO2 for carbon fixation. When CO2 was added, the cells generated more biomass, and AQDS had no stimulatory effect. End products indicated that RDX carbon became CO2, biomass, and a soluble, uncharacterized aqueous metabolite, determined using (14)C-labeled RDX. These data are the first to suggest that photobiological explosives transformation is possible and will provide a framework for which phototrophy can be used in environmental restoration of explosives contaminated water.
Collapse
Affiliation(s)
- Kayleigh A Millerick
- Environmental Engineering and Earth Sciences, Clemson University, 312 Biosystems Research Complex, Clemson, SC 29634, United States; Department of Civil, Environmental & Construction Engineering, Texas Tech University, Lubbock, TX 79409, United States
| | - Juliet T Johnston
- Environmental Engineering and Earth Sciences, Clemson University, 312 Biosystems Research Complex, Clemson, SC 29634, United States
| | - Kevin T Finneran
- Environmental Engineering and Earth Sciences, Clemson University, 312 Biosystems Research Complex, Clemson, SC 29634, United States.
| |
Collapse
|
4
|
Ryan A, Kaplan E, Nebel JC, Polycarpou E, Crescente V, Lowe E, Preston GM, Sim E. Identification of NAD(P)H quinone oxidoreductase activity in azoreductases from P. aeruginosa: azoreductases and NAD(P)H quinone oxidoreductases belong to the same FMN-dependent superfamily of enzymes. PLoS One 2014; 9:e98551. [PMID: 24915188 PMCID: PMC4051601 DOI: 10.1371/journal.pone.0098551] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 05/05/2014] [Indexed: 01/15/2023] Open
Abstract
Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. In most organisms this reaction is carried out by a group of flavoenzymes known as NAD(P)H quinone oxidoreductases. Azoreductases have previously been separate from this group, however using azoreductases from Pseudomonas aeruginosa we show that they can rapidly reduce quinones. Azoreductases from the same organism are also shown to have distinct substrate specificity profiles allowing them to reduce a wide range of quinones. The azoreductase family is also shown to be more extensive than originally thought, due to the large sequence divergence amongst its members. As both NAD(P)H quinone oxidoreductases and azoreductases have related reaction mechanisms it is proposed that they form an enzyme superfamily. The ubiquitous and diverse nature of azoreductases alongside their broad substrate specificity, indicates they play a wide role in cellular survival under adverse conditions.
Collapse
Affiliation(s)
- Ali Ryan
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Elise Kaplan
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Jean-Christophe Nebel
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Elena Polycarpou
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Vincenzo Crescente
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Edward Lowe
- Laboratory of Molecular Biophysics, Biochemistry Department, University of Oxford, Oxford, United Kingdom
| | - Gail M. Preston
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Edith Sim
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| |
Collapse
|
5
|
Devi PP, Adhikari S. Homology modeling and functional sites prediction of azoreductase enzyme from the cyanobacterium Nostoc sp. PCC7120. Interdiscip Sci 2013; 4:310-8. [DOI: 10.1007/s12539-012-0140-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Revised: 05/02/2012] [Accepted: 07/30/2012] [Indexed: 10/27/2022]
|
6
|
Ryan A, Kaplan E, Laurieri N, Lowe E, Sim E. Activation of nitrofurazone by azoreductases: multiple activities in one enzyme. Sci Rep 2011; 1:63. [PMID: 22355582 PMCID: PMC3216550 DOI: 10.1038/srep00063] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 07/28/2011] [Indexed: 11/10/2022] Open
Abstract
Azoreductases are well known for azo pro-drug activation by gut flora. We show that azoreductases have a wider role in drug metabolism than previously thought as they can also reduce and hence activate nitrofurazone. Nitrofurazone, a nitroaromatic drug, is a broad spectrum antibiotic which has until now been considered as activated in bacteria by nitroreductases. The structure of the azoreductase with nitrofurazone bound was solved at 2.08 Å and shows nitrofurazone in an active conformation. Based on the structural information, the kinetics and stoichiometry of nitrofurazone reduction by azoreductase from P. aeruginosa, we propose a mechanism of activation which accounts for the ability of azoreductases to reduce both azo and nitroaromatic drugs. This mode of activation can explain the cytotoxic side-effects of nitrofurazone through human azoreductase homologues.
Collapse
Affiliation(s)
- Ali Ryan
- Pharmacology Department, University of Oxford, OX1 3QT
- Faculty of Science, Engineering and Computing, Kingston University, KT1 2EE
| | - Elise Kaplan
- Pharmacology Department, University of Oxford, OX1 3QT
| | | | - Edward Lowe
- Laboratory of Molecular Biophysics, Biochemistry Department, University of Oxford, OX1 3QU
| | - Edith Sim
- Pharmacology Department, University of Oxford, OX1 3QT
- Faculty of Science, Engineering and Computing, Kingston University, KT1 2EE
| |
Collapse
|
7
|
Molecular determinants of azo reduction activity in the strain Pseudomonas putida MET94. Appl Microbiol Biotechnol 2011; 92:393-405. [DOI: 10.1007/s00253-011-3366-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 04/29/2011] [Accepted: 05/02/2011] [Indexed: 10/18/2022]
|
8
|
Abstract
The group II azoreductase BTI1 utilizes NADPH to directly cleave azo bonds in water-soluble azo dyes, including quenchers of fluorescence. Unexpectedly, optimal reduction was dye specific, ranging from a pH of <5.5 for Janus green B, to pH 6.0 for methyl red, methyl orange, and BHQ-10, to pH >8.3 for flame orange.
Collapse
|