1
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Saunders JW, Damry AM, Vongsouthi V, Spence MA, Frkic RL, Gomez C, Yates PA, Matthews DS, Tokuriki N, McLeod MD, Jackson CJ. Increasing the Soluble Expression and Whole-Cell Activity of the Plastic-Degrading Enzyme MHETase through Consensus Design. Biochemistry 2024; 63:1663-1673. [PMID: 38885634 DOI: 10.1021/acs.biochem.4c00165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
The mono(2-hydroxyethyl) terephthalate hydrolase (MHETase) from Ideonella sakaiensis carries out the second step in the enzymatic depolymerization of poly(ethylene terephthalate) (PET) plastic into the monomers terephthalic acid (TPA) and ethylene glycol (EG). Despite its potential industrial and environmental applications, poor recombinant expression of MHETase has been an obstacle to its industrial application. To overcome this barrier, we developed an assay allowing for the medium-throughput quantification of MHETase activity in cell lysates and whole-cell suspensions, which allowed us to screen a library of engineered variants. Using consensus design, we generated several improved variants that exhibit over 10-fold greater whole-cell activity than wild-type (WT) MHETase. This is revealed to be largely due to increased soluble expression, which biochemical and structural analysis indicates is due to improved protein folding.
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Affiliation(s)
- Jake W Saunders
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Adam M Damry
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Vanessa Vongsouthi
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Matthew A Spence
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Rebecca L Frkic
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence for Innovations in Peptide & Protein Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Chloe Gomez
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Patrick A Yates
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Dana S Matthews
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence for Innovations in Peptide & Protein Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Nobuhiko Tokuriki
- Michael Smith Laboratories, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Malcolm D McLeod
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence for Innovations in Peptide & Protein Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence for Innovations in Synthetic Biology, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
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2
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Diviesti K, Russell-Parks GA, Trewyn BG, Holz RC. Atrazine Degradation Using Immobilized Triazine Hydrolase from Arthrobacter aurescens TC1 in Mesoporous Silica Nanomaterials. ACS ENVIRONMENTAL AU 2023; 3:361-369. [PMID: 38028742 PMCID: PMC10655591 DOI: 10.1021/acsenvironau.3c00036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 12/01/2023]
Abstract
Triazine hydrolase fromArthrobacter aurescens TC1 (TrzN) was successfully immobilized on mesoporous silica nanomaterials (MSNs) for the first time. For both nonfunctionalized MSNs and MSNs functionalized with Zn(II), three pore sizes were evaluated for their ability to immobilize wild-type TrzN: Mobile composition of matter no. 41 (small, 3 nm pores), mesoporous silica nanoparticle material with 10 nm pore diameter (MSN-10) (medium, 6-12 nm pores), and pore-expanded MSN-10 (large, 15-30 nm pores). Of these six TrzN:MSN biomaterials, it was shown that TrzN:MSN-10 was the most active (3.8 ± 0.4 × 10-5 U/mg) toward the hydrolysis of a 50 μM atrazine solution at 25 °C. The TrzN:MSN-10 biomaterial was then coated in chitosan (TrzN:MSN-10:Chit) as chitosan has been shown to increase stability in extreme conditions such as low/high pH, heat shock, and the presence of organic solvents. TrzN:MSN-10:Chit was shown to be a superior TrzN biomaterial to TrzN:MSN-10 as it exhibited higher activity under all storage conditions, in the presence of 20% MeOH, at low and high pH values, and at elevated temperatures up to 80 °C. Finally, the TrzN:MSN-10:Chit biomaterial was shown to be fully active in river water, which establishes it as a functional biomaterial under actual field conditions. A combination of these data indicate that the TrzN:MSN-10:Chit biomaterial exhibited the best overall catalytic profile making it a promising biocatalyst for the bioremediation of atrazine.
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Affiliation(s)
- Karla Diviesti
- Quantitative
Biosciences and Engineering Program, Colorado
School of Mines, 1012
14th Street, Golden, Colorado 80401, United States
| | - Glory A. Russell-Parks
- Department
of Chemistry, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States
| | - Brian G. Trewyn
- Department
of Chemistry, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States
- National
Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, United States
- Materials
Science Program, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States
| | - Richard C. Holz
- Department
of Chemistry, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States
- Quantitative
Biosciences and Engineering Program, Colorado
School of Mines, 1012
14th Street, Golden, Colorado 80401, United States
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3
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Yao T, Sun P, Zhao W. Triazine Herbicides Risk Management Strategies on Environmental and Human Health Aspects Using In-Silico Methods. Int J Mol Sci 2023; 24:ijms24065691. [PMID: 36982765 PMCID: PMC10052965 DOI: 10.3390/ijms24065691] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/09/2023] [Accepted: 03/12/2023] [Indexed: 03/19/2023] Open
Abstract
As an effective herbicide, 1, 3, 5-Triazine herbicides (S-THs) are used widely in the pesticide market. However, due to their chemical properties, S-THs severely threaten the environment and human health (e.g., human lung cytotoxicity). In this study, molecular docking, Analytic Hierarchy Process—Technique for Order Preference by Similarity to the Ideal Solution (AHP-TOPSIS), and a three-dimensional quantitative structure-active relationship (3D-QSAR) model were used to design S-TH substitutes with high herbicidal functionality, high microbial degradability, and low human lung cytotoxicity. We discovered a substitute, Derivative-5, with excellent overall performance. Furthermore, Taguchi orthogonal experiments, full factorial design of experiments, and the molecular dynamics method were used to identify three chemicals (namely, the coexistence of aspartic acid, alanine, and glycine) that could promote the degradation of S-THs in maize cropping fields. Finally, density functional theory (DFT), Estimation Programs Interface (EPI), pharmacokinetic, and toxicokinetic methods were used to further verify the high microbial degradability, favorable aquatic environment, and human health friendliness of Derivative 5. This study provided a new direction for further optimizations of novel pesticide chemicals.
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4
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Catalytic Biomaterials for Atrazine Degradation. Catalysts 2023. [DOI: 10.3390/catal13010140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
In this paper, triazine hydrolase from Arthrobacter aurescens TC1 (TrzN) was successfully immobilized in alginate beads (TrzN:alginate), alginate beads coated in chitosan (TrzN:chitosan), and tetramethylorthosilicate (TMOS) gels using the sol–gel method (TrzN:sol–gel) for the first time. TrzN:alginate and TrzN:chitosan hydrolyzed 50 µM of atrazine in 6 h with negligible protein loss with an ~80% conversion rate. However, the TrzN:sol–gel biomaterial converted >95% of a 50 µM atrazine solution in an hour with negligible protein loss. The treatment of each of these biomaterials with trypsin confirmed that the catalytic activity was due to the encapsulated enzyme and not surface-bound TrzN. All three of the biomaterials showed potential for long-term storage and reuse, with the only limitation arising from the loss of protein in the storage buffer for the TrzN:alginate and TrzN:chitosan biomaterials, not the denaturation of the encapsulated TrzN. TrzN:sol–gel stood out, with ~100% activity being retained after 10 consecutive reactions. Additionally, the materials stayed active in methanol concentrations <10%, suggesting the ability to increase the solubility of atrazine with organic solvents. The structural integrity of the TrzN:alginate and TrzN:chitosan materials became limiting in extreme pH conditions, while TrzN:sol–gel outperformed WT TrzN. Overall, the TrzN:sol–gel biomaterial proved to be the best atrazine dichlorination biocatalyst. As sol–gels can be cast into any desired shape, including pellets, which can be used in columns, the TrzN:sol–gel biomaterial provides a new avenue for the design of bioremediation methodologies for the removal of atrazine from the environment.
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5
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Sasi VM, Ullrich S, Ton J, Fry SE, Johansen-Leete J, Payne RJ, Nitsche C, Jackson CJ. Predicting Antiviral Resistance Mutations in SARS-CoV-2 Main Protease with Computational and Experimental Screening. Biochemistry 2022; 61:2495-2505. [DOI: 10.1021/acs.biochem.2c00489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Vishnu M. Sasi
- Research School of Chemistry, Australian National University, Canberra ACT 2601, Australia
| | - Sven Ullrich
- Research School of Chemistry, Australian National University, Canberra ACT 2601, Australia
| | - Jennifer Ton
- Research School of Chemistry, Australian National University, Canberra ACT 2601, Australia
| | - Sarah E. Fry
- School of Chemistry, The University of Sydney, Sydney NSW 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney NSW 2006, Australia
| | - Jason Johansen-Leete
- School of Chemistry, The University of Sydney, Sydney NSW 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney NSW 2006, Australia
| | - Richard J. Payne
- School of Chemistry, The University of Sydney, Sydney NSW 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney NSW 2006, Australia
| | - Christoph Nitsche
- Research School of Chemistry, Australian National University, Canberra ACT 2601, Australia
| | - Colin J. Jackson
- Research School of Chemistry, Australian National University, Canberra ACT 2601, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, Australian National University, Canberra ACT 2601, Australia
- Australian Research Council Centre of Excellence in Synthetic Biology, Australian National University, Canberra ACT 2601, Australia
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6
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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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7
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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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Sugrue E, Scott C, Jackson CJ. Constrained evolution of a bispecific enzyme: lessons for biocatalyst design. Org Biomol Chem 2017; 15:937-946. [DOI: 10.1039/c6ob02355j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Analysis of the natural evolution of bispecificity in triazine hydrolase highlights the importance of epistasis in protein engineering and evolution.
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Affiliation(s)
- E. Sugrue
- Research School of Chemistry
- Australian National University
- Canberra
- Australia
| | - C. Scott
- Commonwealth Scientific and Industrial Research Organisation
- Canberra
- Australia
| | - C. J. Jackson
- Research School of Chemistry
- Australian National University
- Canberra
- Australia
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9
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Sugrue E, Carr PD, Scott C, Jackson CJ. Active Site Desolvation and Thermostability Trade-Offs in the Evolution of Catalytically Diverse Triazine Hydrolases. Biochemistry 2016; 55:6304-6313. [DOI: 10.1021/acs.biochem.6b00731] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elena Sugrue
- Research
School of Chemistry, Australian National University, Canberra, Australia
| | - Paul D. Carr
- Research
School of Chemistry, Australian National University, Canberra, Australia
| | | | - Colin J. Jackson
- Research
School of Chemistry, Australian National University, Canberra, Australia
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10
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Sugrue E, Hartley CJ, Scott C, Jackson CJ. The Evolution of New Catalytic Mechanisms for Xenobiotic Hydrolysis in Bacterial Metalloenzymes. Aust J Chem 2016. [DOI: 10.1071/ch16426] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
An increasing number of bacterial metalloenzymes have been shown to catalyse the breakdown of xenobiotics in the environment, while others exhibit a variety of promiscuous xenobiotic-degrading activities. Several different evolutionary processes have allowed these enzymes to gain or enhance xenobiotic-degrading activity. In this review, we have surveyed the range of xenobiotic-degrading metalloenzymes, and discuss the molecular and catalytic basis for the development of new activities. We also highlight how our increased understanding of the natural evolution of xenobiotic-degrading metalloenzymes can be been applied to laboratory enzyme design.
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11
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X-Ray Structure and Mutagenesis Studies of the N-Isopropylammelide Isopropylaminohydrolase, AtzC. PLoS One 2015; 10:e0137700. [PMID: 26390431 PMCID: PMC4577212 DOI: 10.1371/journal.pone.0137700] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 08/19/2015] [Indexed: 12/01/2022] Open
Abstract
The N-isopropylammelide isopropylaminohydrolase from Pseudomonas sp. strain ADP, AtzC, provides the third hydrolytic step in the mineralization of s-triazine herbicides, such as atrazine. We obtained the X-ray crystal structure of AtzC at 1.84 Å with a weak inhibitor bound in the active site and then used a combination of in silico docking and site-directed mutagenesis to understand the interactions between AtzC and its substrate, isopropylammelide. The substitution of an active site histidine residue (His249) for an alanine abolished the enzyme’s catalytic activity. We propose a plausible catalytic mechanism, consistent with the biochemical and crystallographic data obtained that is similar to that found in carbonic anhydrase and other members of subtype III of the amidohydrolase family
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12
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Peat TS, Newman J, Balotra S, Lucent D, Warden AC, Scott C. The structure of the hexameric atrazine chlorohydrolase AtzA. ACTA ACUST UNITED AC 2015; 71:710-20. [PMID: 25760618 PMCID: PMC4356373 DOI: 10.1107/s1399004715000619] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/12/2015] [Indexed: 12/05/2022]
Abstract
The structure of atrazine chlorohydrolase (AtzA) is presented and is used to reinterpret data from genetic, biochemical and evolutionary studies, providing insight into why this recently evolved enzyme appears to be poorly adapted for its physiological substrate compared with the alternative metal-dependent atrazine dechlorinase TrzN. Atrazine chlorohydrolase (AtzA) was discovered and purified in the early 1990s from soil that had been exposed to the widely used herbicide atrazine. It was subsequently found that this enzyme catalyzes the first and necessary step in the breakdown of atrazine by the soil organism Pseudomonas sp. strain ADP. Although it has taken 20 years, a crystal structure of the full hexameric form of AtzA has now been obtained. AtzA is less well adapted to its physiological role (i.e. atrazine dechlorination) than the alternative metal-dependent atrazine chlorohydrolase (TrzN), with a substrate-binding pocket that is under considerable strain and for which the substrate is a poor fit.
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Affiliation(s)
- T S Peat
- CSIRO Biomedical Manufacturing, Parkville, Australia
| | - J Newman
- CSIRO Biomedical Manufacturing, Parkville, Australia
| | - S Balotra
- Research School of Chemistry, Australian National University, Canberra, Australia
| | - D Lucent
- Division of Engineering and Physics, Wilkes University, Wilkes-Barr, Pennsylvania, USA
| | - A C Warden
- CSIRO Land and Water Flagship, Black Mountain, Canberra, Australia
| | - C Scott
- CSIRO Biomedical Manufacturing, Parkville, Australia
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13
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Evolutionary expansion of the amidohydrolase superfamily in bacteria in response to the synthetic compounds molinate and diuron. Appl Environ Microbiol 2015; 81:2612-24. [PMID: 25636851 DOI: 10.1128/aem.04016-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The amidohydrolase superfamily has remarkable functional diversity, with considerable structural and functional annotation of known sequences. In microbes, the recent evolution of several members of this family to catalyze the breakdown of environmental xenobiotics is not well understood. An evolutionary transition from binuclear to mononuclear metal ion coordination at the active sites of these enzymes could produce large functional changes such as those observed in nature, but there are few clear examples available to support this hypothesis. To investigate the role of binuclear-mononuclear active-site transitions in the evolution of new function in this superfamily, we have characterized two recently evolved enzymes that catalyze the hydrolysis of the synthetic herbicides molinate (MolA) and phenylurea (PuhB). In this work, the crystal structures, mutagenesis, metal ion analysis, and enzyme kinetics of both MolA and PuhB establish that these enzymes utilize a mononuclear active site. However, bioinformatics and structural comparisons reveal that the closest putative ancestor of these enzymes had a binuclear active site, indicating that a binuclear-mononuclear transition has occurred. These proteins may represent examples of evolution modifying the characteristics of existing catalysts to satisfy new requirements, specifically, metal ion rearrangement leading to large leaps in activity that would not otherwise be possible.
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14
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X-ray structure of the amidase domain of AtzF, the allophanate hydrolase from the cyanuric acid-mineralizing multienzyme complex. Appl Environ Microbiol 2014; 81:470-80. [PMID: 25362066 DOI: 10.1128/aem.02783-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The activity of the allophanate hydrolase from Pseudomonas sp. strain ADP, AtzF, provides the final hydrolytic step for the mineralization of s-triazines, such as atrazine and cyanuric acid. Indeed, the action of AtzF provides metabolic access to two of the three nitrogens in each triazine ring. The X-ray structure of the N-terminal amidase domain of AtzF reveals that it is highly homologous to allophanate hydrolases involved in a different catabolic process in other organisms (i.e., the mineralization of urea). The smaller C-terminal domain does not appear to have a physiologically relevant catalytic function, as reported for the allophanate hydrolase of Kluyveromyces lactis, when purified enzyme was tested in vitro. However, the C-terminal domain does have a function in coordinating the quaternary structure of AtzF. Interestingly, we also show that AtzF forms a large, ca. 660-kDa, multienzyme complex with AtzD and AtzE that is capable of mineralizing cyanuric acid. The function of this complex may be to channel substrates from one active site to the next, effectively protecting unstable metabolites, such as allophanate, from solvent-mediated decarboxylation to a dead-end metabolic product.
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