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Zhou N, Wang J, Wang W, Wu X. Purification, characterization, and catalytic mechanism of N-Isopropylammelide isopropylaminohydrolase (AtzC) involved in the degradation of s-triazine herbicides. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 268:115803. [PMID: 33158617 DOI: 10.1016/j.envpol.2020.115803] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 10/06/2020] [Accepted: 10/08/2020] [Indexed: 06/11/2023]
Abstract
Deamination is ubiquitous in nature and has important biological significance. Leucobacter triazinivorans JW-1, recently isolated from sludge, can rapidly degrade s-triazine herbicides. The responsible enzymes, however, have not been purified and characterized. Herein, we purified an amidohydrolase, i.e., N-isopropylammelide isopropylaminohydrolase (AtzC) from JW-1 cells by ammonium sulfate precipitation and three chromatography steps. The purified AtzC catalyzed amidohydrolysis of N-isopropylammelide to cyanuric acid. The optimal catalytic conditions of the purified AtzC were 42 °C and pH 7.0, and the Km and Vmax of AtzC was 0.811 mM and 28.19 mmol/min·mg. AtzC could catalyze amidohydrolysis of an N-alkyl substituent from dihydroxy s-triazines to cyanuric acid. Molecular docking and structural alignments were used to infer AtzC catalytic mechanism. The structural architecture of AtzC resembled that of cytosine deaminase in class III amidohydrolase, with a single Zn2+ coordinated by His and Asp. Interestingly, the AtzC lacks an acidic residue putatively to activate water for hydrolysis as compared to the other amidohydrolases. His253 in AtzC probably functions as a single general acid-base catalyst. These findings further enhance our understanding how aminohydrolases catalyze the metabolism of s-triazine herbicides.
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Affiliation(s)
- Nan Zhou
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei, 230036, China
| | - Jie Wang
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei, 230036, China
| | - Wenbo Wang
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei, 230036, China
| | - Xiangwei Wu
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei, 230036, China.
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Esquirol L, Peat TS, Sugrue E, Balotra S, Rottet S, Warden AC, Wilding M, Hartley CJ, Jackson CJ, Newman J, Scott C. Bacterial catabolism of s-triazine herbicides: biochemistry, evolution and application. Adv Microb Physiol 2020; 76:129-186. [PMID: 32408946 DOI: 10.1016/bs.ampbs.2020.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The synthetic s-triazines are abundant, nitrogen-rich, heteroaromatic compounds used in a multitude of applications including, herbicides, plastics and polymers, and explosives. Their presence in the environment has led to the evolution of bacterial catabolic pathways in bacteria that allow use of these anthropogenic chemicals as a nitrogen source that supports growth. Herbicidal s-triazines have been used since the mid-twentieth century and are among the most heavily used herbicides in the world, despite being withdrawn from use in some areas due to concern about their safety and environmental impact. Bacterial catabolism of the herbicidal s-triazines has been studied extensively. Pseudomonas sp. strain ADP, which was isolated more than thirty years after the introduction of the s-triazine herbicides, has been the model system for most of these studies; however, several alternative catabolic pathways have also been identified. Over the last five years, considerable detail about the molecular mode of action of the s-triazine catabolic enzymes has been uncovered through acquisition of their atomic structures. These structural studies have also revealed insights into the evolutionary origins of this newly acquired metabolic capability. In addition, s-triazine-catabolizing bacteria and enzymes have been used in a range of applications, including bioremediation of herbicides and cyanuric acid, introducing metabolic resistance to plants, and as a novel selectable marker in fermentation organisms. In this review, we cover the discovery and characterization of bacterial strains, metabolic pathways and enzymes that catabolize the s-triazines. We also consider the evolution of these new enzymes and pathways and discuss the practical applications that have been considered for these bacteria and enzymes. One Sentence Summary: A detailed understanding of bacterial herbicide catabolic enzymes and pathways offer new evolutionary insights and novel applied tools.
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Affiliation(s)
- Lygie Esquirol
- Biocatalysis & Synthetic Biology Team, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia; Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Thomas S Peat
- CSIRO Biomedical Manufacturing, Parkville, VIC, Australia
| | - Elena Sugrue
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Sahil Balotra
- Biocatalysis & Synthetic Biology Team, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia
| | - Sarah Rottet
- Biocatalysis & Synthetic Biology Team, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia; Synthetic Biology Future Science Platform, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia
| | - Andrew C Warden
- Biocatalysis & Synthetic Biology Team, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia
| | - Matthew Wilding
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia; CSIRO Biomedical Manufacturing, Parkville, VIC, Australia; Synthetic Biology Future Science Platform, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia
| | - Carol J Hartley
- Biocatalysis & Synthetic Biology Team, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia
| | - Colin J Jackson
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Janet Newman
- CSIRO Biomedical Manufacturing, Parkville, VIC, Australia
| | - Colin Scott
- Biocatalysis & Synthetic Biology Team, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia; Synthetic Biology Future Science Platform, CSIRO Land & Water, Black Mountain Science and Innovation Park, Canberra, ACT, Australia
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Dennis ML, Esquirol L, Nebl T, Newman J, Scott C, Peat TS. The evolving story of AtzT, a periplasmic binding protein. Acta Crystallogr D Struct Biol 2019; 75:995-1002. [PMID: 31692473 PMCID: PMC6834077 DOI: 10.1107/s2059798319013883] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Accepted: 10/11/2019] [Indexed: 11/20/2022] Open
Abstract
Atrazine is an s-triazine-based herbicide that is used in many countries around the world in many millions of tons per year. A small number of organisms, such as Pseudomonas sp. strain ADP, have evolved to use this modified s-triazine as a food source, and the various genes required to metabolize atrazine can be found on a single plasmid. The atomic structures of seven of the eight proteins involved in the breakdown of atrazine by Pseudomonas sp. strain ADP have been determined by X-ray crystallography, but the structures of the proteins required by the cell to import atrazine for use as an energy source are still lacking. The structure of AtzT, a periplasmic binding protein that may be involved in the transport of a derivative of atrazine, 2-hydroxyatrazine, into the cell for mineralization, has now been determined. The structure was determined by SAD phasing using an ethylmercury phosphate derivative that diffracted X-rays to beyond 1.9 Å resolution. `Native' (guanine-bound) and 2-hydroxyatrazine-bound structures were also determined to high resolution (1.67 and 1.65 Å, respectively), showing that 2-hydroxyatrazine binds in a similar way to the purportedly native ligand. Structural similarities led to the belief that it may be possible to evolve AtzT from a purine-binding protein to a protein that can bind and detect atrazine in the environment.
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Affiliation(s)
- Matthew L. Dennis
- Biomedical Manufacturing Program, CSIRO, 343 Royal Parade, Parkville, VIC 3052, Australia
| | - Lygie Esquirol
- CSIRO Synthetic Biology Future Science Platform, GPO Box 1700, Acton, Canberra, ACT 2601, Australia
| | - Tom Nebl
- Biomedical Manufacturing Program, CSIRO, 343 Royal Parade, Parkville, VIC 3052, Australia
| | - Janet Newman
- Biomedical Manufacturing Program, CSIRO, 343 Royal Parade, Parkville, VIC 3052, Australia
| | - Colin Scott
- CSIRO Synthetic Biology Future Science Platform, GPO Box 1700, Acton, Canberra, ACT 2601, Australia
| | - Thomas S. Peat
- Biomedical Manufacturing Program, CSIRO, 343 Royal Parade, Parkville, VIC 3052, Australia
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Esquirol L, Peat TS, Wilding M, Liu JW, French NG, Hartley CJ, Onagi H, Nebl T, Easton CJ, Newman J, Scott C. An unexpected vestigial protein complex reveals the evolutionary origins of an s-triazine catabolic enzyme. J Biol Chem 2018. [PMID: 29523689 DOI: 10.1074/jbc.ra118.001996] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyanuric acid is a metabolic intermediate of s-triazines, such as atrazine (a common herbicide) and melamine (used in resins and plastics). Cyanuric acid is mineralized to ammonia and carbon dioxide by the soil bacterium Pseudomonas sp. strain ADP via three hydrolytic enzymes (AtzD, AtzE, and AtzF). Here, we report the purification and biochemical and structural characterization of AtzE. Contrary to previous reports, we found that AtzE is not a biuret amidohydrolase, but instead it catalyzes the hydrolytic deamination of 1-carboxybiuret. X-ray crystal structures of apo AtzE and AtzE bound with the suicide inhibitor phenyl phosphorodiamidate revealed that the AtzE enzyme complex consists of two independent molecules in the asymmetric unit. We also show that AtzE forms an α2β2 heterotetramer with a previously unidentified 68-amino acid-long protein (AtzG) encoded in the cyanuric acid mineralization operon from Pseudomonas sp. strain ADP. Moreover, we observed that AtzG is essential for the production of soluble, active AtzE and that this obligate interaction is a vestige of their shared evolutionary origin. We propose that AtzEG was likely recruited into the cyanuric acid-mineralizing pathway from an ancestral glutamine transamidosome that required protein-protein interactions to enforce the exclusion of solvent from the transamidation reaction.
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Affiliation(s)
- Lygie Esquirol
- From the Biocatalysis and Synthetic Biology Team and.,the Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, and
| | - Thomas S Peat
- CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria 3052, Australia
| | - Matthew Wilding
- the Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, and.,CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria 3052, Australia
| | - Jian-Wei Liu
- From the Biocatalysis and Synthetic Biology Team and
| | | | | | - Hideki Onagi
- the Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, and
| | - Thomas Nebl
- CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria 3052, Australia
| | - Christopher J Easton
- the Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, and
| | - Janet Newman
- CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria 3052, Australia
| | - Colin Scott
- From the Biocatalysis and Synthetic Biology Team and .,Synthetic Biology Future Science Platform, CSIRO Land and Water, Canberra, Australian Capital Territory 2601
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5
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Esquirol L, Peat TS, Wilding M, Lucent D, French NG, Hartley CJ, Newman J, Scott C. Structural and biochemical characterization of the biuret hydrolase (BiuH) from the cyanuric acid catabolism pathway of Rhizobium leguminasorum bv. viciae 3841. PLoS One 2018; 13:e0192736. [PMID: 29425231 PMCID: PMC5806882 DOI: 10.1371/journal.pone.0192736] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/29/2018] [Indexed: 11/24/2022] Open
Abstract
Biuret deamination is an essential step in cyanuric acid mineralization. In the well-studied atrazine degrading bacterium Pseudomonas sp. strain ADP, the amidase AtzE catalyzes this step. However, Rhizobium leguminosarum bv. viciae 3841 uses an unrelated cysteine hydrolase, BiuH, instead. Herein, structures of BiuH, BiuH with bound inhibitor and variants of BiuH are reported. The substrate is bound in the active site by a hydrogen bonding network that imparts high substrate specificity. The structure of the inactive Cys175Ser BiuH variant with substrate bound in the active site revealed that an active site cysteine (Cys175), aspartic acid (Asp36) and lysine (Lys142) form a catalytic triad, which is consistent with biochemical studies of BiuH variants. Finally, molecular dynamics simulations highlighted the presence of three channels from the active site to the enzyme surface: a persistent tunnel gated by residues Val218 and Gln215 forming a potential substrate channel and two smaller channels formed by Val28 and a mobile loop (including residues Phe41, Tyr47 and Met51) that may serve as channels for co-product (ammonia) or co-substrate (water).
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Affiliation(s)
- Lygie Esquirol
- CSIRO Biocatalysis and Synthetic Biology, Canberra, Australian Capital Territory, Australia
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Thomas S. Peat
- CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria, Australia
| | - Matthew Wilding
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
- CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria, Australia
| | - Del Lucent
- Department of Electrical Engineering and Physics, Wilkes University, Wilkes-Barre, Pennsylvania, United States of America
| | - Nigel G. French
- CSIRO Biocatalysis and Synthetic Biology, Canberra, Australian Capital Territory, Australia
| | - Carol J. Hartley
- CSIRO Biocatalysis and Synthetic Biology, Canberra, Australian Capital Territory, Australia
| | - Janet Newman
- CSIRO Biomedical Manufacturing, Parkville, Melbourne, Victoria, Australia
| | - Colin Scott
- CSIRO Biocatalysis and Synthetic Biology, Canberra, Australian Capital Territory, Australia
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