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Lane TR, Koebel D, Lucas E, Moyer R, Ekins S. In Vitro Characterization and Rescue of VX Metabolism in Human Liver Microsomes. Drug Metab Dispos 2024; 52:574-579. [PMID: 38594080 DOI: 10.1124/dmd.124.001695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 04/03/2024] [Accepted: 04/05/2024] [Indexed: 04/11/2024] Open
Abstract
Venomous agent X (VX) is an organophosphate acetylcholinesterase (AChE) inhibitor, and although it is one of the most toxic AChE inhibitors known, the extent of metabolism in humans is not currently well understood. The known metabolism in humans is limited to the metabolite identification from a single victim of the Osaka poisoning in 1994, which allowed for the identification of several metabolic products. VX has been reported to be metabolized in vitro by paraoxonase-1 and phosphotriesterase, although their binding constants are many orders of magnitude above the LD50, suggesting limited physiologic relevance. Using incubation with human liver microsomes (HLMs), we have now characterized the metabolism of VX and the formation of multiple metabolites as well as identified a Food and Drug Administration-approved drug [ethylenediaminetetraacetic acid (EDTA)] that enhances the metabolic rate. HLM incubation alone shows a pronounced increase in the metabolism of VX compared with buffer, suggesting that cytochrome P450-mediated metabolism of VX is occurring. We identified a biphasic decay with two distinct rates of metabolism. The enhancement of VX metabolism in multiple buffers was assessed to attempt to mitigate the effect of hydrolysis rates. The formation of VX metabolites was shown to be shifted with HLMs, suggesting a pathway enhancement over simple hydrolysis. Additionally, our investigation of hydrolysis rates in various common buffers used in biologic assays discovered dramatic differences in VX stability. The new human in vitro VX metabolic data reported points to a potential in vivo treatment strategy (EDTA) for rescue in individuals that are poisoned though enhancement of metabolism alongside existing treatments. SIGNIFICANCE STATEMENT: Venomous agent X (VX) is a potent acetylcholinesterase inhibitor and chemical weapon. To date, we do not possess a clear understanding of its metabolism in humans that would assist us in treating those exposed to it. This study now describes the human liver microsomal metabolism of VX and identifies ethylenediaminetetraacetic acid, which appears to enhance the rate of metabolism. This may provide a potential treatment option for human VX poisoning.
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Affiliation(s)
- Thomas R Lane
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina (T.R.L., S.E.) and Battelle Memorial Institute, Columbus, Ohio (D.K., E.L., R.M.)
| | - David Koebel
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina (T.R.L., S.E.) and Battelle Memorial Institute, Columbus, Ohio (D.K., E.L., R.M.)
| | - Eric Lucas
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina (T.R.L., S.E.) and Battelle Memorial Institute, Columbus, Ohio (D.K., E.L., R.M.)
| | - Robert Moyer
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina (T.R.L., S.E.) and Battelle Memorial Institute, Columbus, Ohio (D.K., E.L., R.M.)
| | - Sean Ekins
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina (T.R.L., S.E.) and Battelle Memorial Institute, Columbus, Ohio (D.K., E.L., R.M.)
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2
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Dym O, Aggarwal N, Ashani Y, Leader H, Albeck S, Unger T, Hamer-Rogotner S, Silman I, Tawfik DS, Sussman JL. The impact of molecular variants, crystallization conditions and the space group on ligand-protein complexes: a case study on bacterial phosphotriesterase. Acta Crystallogr D Struct Biol 2023; 79:992-1009. [PMID: 37860961 PMCID: PMC10619419 DOI: 10.1107/s2059798323007672] [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] [Received: 07/18/2023] [Accepted: 09/03/2023] [Indexed: 10/21/2023] Open
Abstract
A bacterial phosphotriesterase was employed as an experimental paradigm to examine the effects of multiple factors, such as the molecular constructs, the ligands used during protein expression and purification, the crystallization conditions and the space group, on the visualization of molecular complexes of ligands with a target enzyme. In this case, the ligands used were organophosphates that are fragments of the nerve agents and insecticides on which the enzyme acts as a bioscavenger. 12 crystal structures of various phosphotriesterase constructs obtained by directed evolution were analyzed, with resolutions of up to 1.38 Å. Both apo forms and holo forms, complexed with the organophosphate ligands, were studied. Crystals obtained from three different crystallization conditions, crystallized in four space groups, with and without N-terminal tags, were utilized to investigate the impact of these factors on visualizing the organophosphate complexes of the enzyme. The study revealed that the tags used for protein expression can lodge in the active site and hinder ligand binding. Furthermore, the space group in which the protein crystallizes can significantly impact the visualization of bound ligands. It was also observed that the crystallization precipitants can compete with, and even preclude, ligand binding, leading to false positives or to the incorrect identification of lead drug candidates. One of the co-crystallization conditions enabled the definition of the spaces that accommodate the substituents attached to the P atom of several products of organophosphate substrates after detachment of the leaving group. The crystal structures of the complexes of phosphotriesterase with the organophosphate products reveal similar short interaction distances of the two partially charged O atoms of the P-O bonds with the exposed β-Zn2+ ion and the buried α-Zn2+ ion. This suggests that both Zn2+ ions have a role in stabilizing the transition state for substrate hydrolysis. Overall, this study provides valuable insights into the challenges and considerations involved in studying the crystal structures of ligand-protein complexes, highlighting the importance of careful experimental design and rigorous data analysis in ensuring the accuracy and reliability of the resulting phosphotriesterase-organophosphate structures.
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Affiliation(s)
- Orly Dym
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Nidhi Aggarwal
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Yacov Ashani
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Haim Leader
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Shira Albeck
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Tamar Unger
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Shelly Hamer-Rogotner
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Israel Silman
- Department of Brain Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Dan S. Tawfik
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Joel L. Sussman
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot, Israel
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3
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Job L, Köhler A, Testanera M, Escher B, Worek F, Skerra A. Engineering of a phosphotriesterase with improved stability and enhanced activity for detoxification of the pesticide metabolite malaoxon. Protein Eng Des Sel 2023; 36:gzad020. [PMID: 37941439 DOI: 10.1093/protein/gzad020] [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] [Received: 08/03/2023] [Revised: 10/30/2023] [Accepted: 11/03/2023] [Indexed: 11/10/2023] Open
Abstract
Organophosphorus (OP) pesticides are still widely applied but pose a severe toxicological threat if misused. For in vivo detoxification, the application of hydrolytic enzymes potentially offers a promising treatment. A well-studied example is the phosphotriesterase of Brevundimonas diminuta (BdPTE). Whereas wild-type BdPTE can hydrolyse pesticides like paraoxon, chlorpyrifos-oxon and mevinphos with high catalytic efficiencies, kcat/KM >2 × 107 M-1 min-1, degradation of malaoxon is unsatisfactory (kcat/KM ≈ 1 × 104 M-1 min-1). Here, we report the rational engineering of BdPTE mutants with improved properties and their efficient production in Escherichia coli. As result, the mutant BdPTE(VRNVVLARY) exhibits 37-fold faster malaoxon hydrolysis (kcat/KM = 4.6 × 105 M-1 min-1), together with enhanced expression yield, improved thermal stability and reduced susceptibility to oxidation. Therefore, this BdPTE mutant constitutes a powerful candidate to develop a biocatalytic antidote for the detoxification of this common pesticide metabolite as well as related OP compounds.
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Affiliation(s)
- Laura Job
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising, Germany
| | - Anja Köhler
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising, Germany
- Institut für Pharmakologie und Toxikologie der Bundeswehr, Neuherbergstr, 11, 80937 München, Germany
| | - Mauricio Testanera
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising, Germany
| | - Benjamin Escher
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising, Germany
| | - Franz Worek
- Institut für Pharmakologie und Toxikologie der Bundeswehr, Neuherbergstr, 11, 80937 München, Germany
| | - Arne Skerra
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising, Germany
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4
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Wang L, Sun Y. Engineering organophosphate hydrolase for enhanced biocatalytic performance: A review. Biochem Eng J 2021. [DOI: 10.1016/j.bej.2021.107945] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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5
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Lyagin I, Efremenko E. Enzymes, Reacting with Organophosphorus Compounds as Detoxifiers: Diversity and Functions. Int J Mol Sci 2021; 22:1761. [PMID: 33578824 PMCID: PMC7916636 DOI: 10.3390/ijms22041761] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 01/05/2023] Open
Abstract
Organophosphorus compounds (OPCs) are able to interact with various biological targets in living organisms, including enzymes. The binding of OPCs to enzymes does not always lead to negative consequences for the body itself, since there are a lot of natural biocatalysts that can catalyze the chemical transformations of the OPCs via hydrolysis or oxidation/reduction and thereby provide their detoxification. Some of these enzymes, their structural differences and identity, mechanisms, and specificity of catalytic action are discussed in this work, including results of computational modeling. Phylogenetic analysis of these diverse enzymes was specially realized for this review to emphasize a great area for future development(s) and applications.
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Affiliation(s)
| | - Elena Efremenko
- Faculty of Chemistry, Lomonosov Moscow State University, Lenin Hills 1/3, 119991 Moscow, Russia;
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6
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On-spot biosensing device for organophosphate pesticide residue detection in fruits and vegetables. CURRENT RESEARCH IN BIOTECHNOLOGY 2021. [DOI: 10.1016/j.crbiot.2021.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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7
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Organophosphorus Nerve Agents: Types, Toxicity, and Treatments. J Toxicol 2020; 2020:3007984. [PMID: 33029136 PMCID: PMC7527902 DOI: 10.1155/2020/3007984] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 08/30/2020] [Accepted: 09/10/2020] [Indexed: 01/08/2023] Open
Abstract
Organophosphorus compounds are extensively used worldwide as pesticides which cause great hazards to human health. Nerve agents, a subcategory of the organophosphorus compounds, have been produced and used during wars, and they have also been used in terrorist activities. These compounds possess physiological threats by interacting and inhibiting acetylcholinesterase enzyme which leads to the cholinergic crisis. After a general introduction, this review elucidates the mechanisms underlying cholinergic and noncholinergic effects of organophosphorus compounds. The conceivable treatment strategies for organophosphate poisoning are different types of bioscavengers which include stoichiometric, catalytic, and pseudocatalytic. The current research on the promising treatments specifically the catalytic bioscavengers including several wild-type organophosphate hydrolases such as paraoxonase and phosphotriesterase, phosphotriesterase-like lactonase, methyl parathion hydrolase, organophosphate acid anhydrolase, diisopropyl fluorophosphatase, human triphosphate nucleotidohydrolase, and senescence marker protein has been widely discussed. Organophosphorus compounds are reported to be the nonphysiological substrate for many mammalian organophosphate hydrolysing enzymes; therefore, the efficiency of these enzymes toward these compounds is inadequate. Hence, studies have been conducted to create mutants with an enhanced rate of hydrolysis and high specificity. Several mutants have been created by applying directed molecular evolution and/or targeted mutagenesis, and catalytic efficiency has been characterized. Generally, organophosphorus compounds are chiral in nature. The development of mutant enzymes for providing superior stereoselective degradation of toxic organophosphorus compounds has also been widely accounted for in this review. Existing enzymes have shown limited efficiency; hence, more effective treatment strategies have also been critically analyzed.
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8
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Katyal P, Chu S, Montclare JK. Enhancing organophosphate hydrolase efficacy via protein engineering and immobilization strategies. Ann N Y Acad Sci 2020; 1480:54-72. [PMID: 32814367 DOI: 10.1111/nyas.14451] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 06/21/2020] [Accepted: 07/07/2020] [Indexed: 01/30/2023]
Abstract
Organophosphorus compounds (OPs), developed as pesticides and chemical warfare agents, are extremely toxic chemicals that pose a public health risk. Of the different detoxification strategies, organophosphate-hydrolyzing enzymes have attracted much attention, providing a potential route for detoxifying those exposed to OPs. Phosphotriesterase (PTE), also known as organophosphate hydrolase (OPH), is one such enzyme that has been extensively studied as a catalytic bioscavenger. In this review, we will discuss the protein engineering of PTE aimed toward improving the activity and stability of the enzyme. In order to make enzyme utilization in OP detoxification more favorable, enzyme immobilization provides an effective means to increase enzyme activity and stability. Here, we present several such strategies that enhance the storage and operational stability of PTE/OPH.
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Affiliation(s)
- Priya Katyal
- Department of Chemical and Biomolecular Engineering, New York University, Tandon School of Engineering, Brooklyn, New York
| | - Stanley Chu
- Department of Chemical and Biomolecular Engineering, New York University, Tandon School of Engineering, Brooklyn, New York
| | - Jin Kim Montclare
- Department of Chemical and Biomolecular Engineering, New York University, Tandon School of Engineering, Brooklyn, New York.,Department of Radiology, New York University Langone Health, New York, New York.,Department of Biomaterials, New York University College of Dentistry, New York, New York.,Department of Chemistry, New York University, New York, New York
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9
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Theoretical Study of VX Hydrolysis Mechanism Catalyzed by Phosphotriesterase Mutant H254R. ChemistrySelect 2020. [DOI: 10.1002/slct.202002112] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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10
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Abstract
The role of phosphotriesterase as an enzyme which is able to hydrolyze organophosphate compounds cannot be disputed. Contamination by organophosphate (OP) compounds in the environment is alarming, and even more worrying is the toxicity of this compound, which affects the nervous system. Thus, it is important to find a safer way to detoxify, detect and recuperate from the toxicity effects of this compound. Phosphotriesterases (PTEs) are mostly isolated from soil bacteria and are classified as metalloenzymes or metal-dependent enzymes that contain bimetals at the active site. There are three separate pockets to accommodate the substrate into the active site of each PTE. This enzyme generally shows a high catalytic activity towards phosphotriesters. These microbial enzymes are robust and easy to manipulate. Currently, PTEs are widely studied for the detection, detoxification, and enzyme therapies for OP compound poisoning incidents. The discovery and understanding of PTEs would pave ways for greener approaches in biotechnological applications and to solve environmental issues relating to OP contamination.
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11
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Jain M, Yadav P, Joshi A, Kodgire P. Advances in detection of hazardous organophosphorus compounds using organophosphorus hydrolase based biosensors. Crit Rev Toxicol 2019; 49:387-410. [DOI: 10.1080/10408444.2019.1626800] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Monika Jain
- Discipline of Biosciences and Biomedical Engineering, Indian Institute of Technology, Indore, India
| | - Priyanka Yadav
- Discipline of Biosciences and Biomedical Engineering, Indian Institute of Technology, Indore, India
| | - Abhijeet Joshi
- Discipline of Biosciences and Biomedical Engineering, Indian Institute of Technology, Indore, India
| | - Prashant Kodgire
- Discipline of Biosciences and Biomedical Engineering, Indian Institute of Technology, Indore, India
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12
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The evolution of phosphotriesterase for decontamination and detoxification of organophosphorus chemical warfare agents. Chem Biol Interact 2019; 308:80-88. [PMID: 31100274 DOI: 10.1016/j.cbi.2019.05.023] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/22/2019] [Accepted: 05/13/2019] [Indexed: 11/23/2022]
Abstract
The organophosphorus chemical warfare agents were initially synthesized in the 1930's and are some of the most toxic compounds ever discovered. The standard means of decontamination are either harsh chemical hydrolysis or high temperature incineration. Given the continued use of chemical warfare agents there are ongoing efforts to develop gentle environmentally friendly means of decontamination and medical counter measures to chemical warfare agent intoxication. Enzymatic decontamination offers the benefits of extreme specificity and mild conditions, allowing their use for both environmental and medical applications. The most promising enzyme for decontamination of the organophosphorus chemical warfare agents is the enzyme phosphotriesterase from Pseudomonas diminuta. However, the catalytic activity of the wild-type enzyme with the chemical warfare agents falls far below that seen with its best substrates, and its stereochemical preference is for the less toxic enantiomer of the chiral phosphorus center found in most chemical warfare agents. Rational design efforts have succeeded in the dramatic improvement of the stereochemical preference of PTE for the more toxic enantiomers. Directed evolution experiments, including site-saturation mutagenesis, targeted error-prone PCR, computational design, and quantitative library analysis, have systematically improved the catalytic activity against the chemical warfare nerve agents. These efforts have resulted in greater than 4-orders of magnitude improvement in catalytic activity and have led to the identification of variants that are highly effective at detoxifying both G-type and V-type nerve agents. The best of these variants have the ability to prevent intoxication when delivered as a post-exposure treatment for VX and as a pre-exposure treatment for G-agent intoxication with observed protective factors up to 60-fold. Combining the best variant, H257Y/L303T, with a PCB polymer coating has enabled the development of a long lasting circulating prophylactic treatment that is highly effective against sarin.
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13
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Bigley AN, Desormeaux E, Xiang DF, Bae SY, Harvey SP, Raushel FM. Overcoming the Challenges of Enzyme Evolution To Adapt Phosphotriesterase for V-Agent Decontamination. Biochemistry 2019; 58:2039-2053. [DOI: 10.1021/acs.biochem.9b00097] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrew N. Bigley
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Emily Desormeaux
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Dao Feng Xiang
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Sue Y. Bae
- U.S. Army Edgewood Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, Maryland 21010, United States
| | - Steven P. Harvey
- U.S. Army Edgewood Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, Maryland 21010, United States
| | - Frank M. Raushel
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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14
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Application of Microbial Cleaning Technology for Removal of Surface Contamination. DEVELOPMENTS IN SURFACE CONTAMINATION AND CLEANING: APPLICATIONS OF CLEANING TECHNIQUES 2019. [PMCID: PMC7149890 DOI: 10.1016/b978-0-12-815577-6.00015-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Microbial cleaning takes advantage of naturally-occurring microbes to remove a wide variety of contaminants from various surfaces. The method is based on the affinity of microbes for hydrocarbons that are digested, producing harmless carbon dioxide, water, and soluble fatty acids. The microbes are nonpathogenic and are safe to handle and dispose. The process is environmentally-friendly and is less expensive than solvent cleaning, but it is not applicable to high precision cleaning applications. Typical applications include parts washing; oil and grease removal from concrete and other floor surfaces, and from drains and grease traps; cleaning and disinfection in healthcare facilities; cleaning of historical artworks and structures; and household and institutional cleaning applications.
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15
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Catalytic bioscavengers as countermeasures against organophosphate nerve agents. Chem Biol Interact 2018; 292:50-64. [DOI: 10.1016/j.cbi.2018.07.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 07/04/2018] [Accepted: 07/06/2018] [Indexed: 12/30/2022]
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16
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Iyengar ARS, Pande AH. Organophosphate-Hydrolyzing Enzymes as First-Line of Defence Against Nerve Agent-Poisoning: Perspectives and the Road Ahead. Protein J 2016; 35:424-439. [DOI: 10.1007/s10930-016-9686-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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17
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Protecting enzymatic function through directed packaging into bacterial outer membrane vesicles. Sci Rep 2016; 6:24866. [PMID: 27117743 PMCID: PMC4846811 DOI: 10.1038/srep24866] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 04/06/2016] [Indexed: 12/11/2022] Open
Abstract
Bacteria possess innate machinery to transport extracellular cargo between cells as well as package virulence factors to infect host cells by secreting outer membrane vesicles (OMVs) that contain small molecules, proteins, and genetic material. These robust proteoliposomes have evolved naturally to be resistant to degradation and provide a supportive environment to extend the activity of encapsulated cargo. In this study, we sought to exploit bacterial OMV formation to package and maintain the activity of an enzyme, phosphotriesterase (PTE), under challenging storage conditions encountered for real world applications. Here we show that OMV packaged PTE maintains activity over free PTE when subjected to elevated temperatures (>100-fold more activity after 14 days at 37 °C), iterative freeze-thaw cycles (3.4-fold post four-cycles), and lyophilization (43-fold). We also demonstrate how lyophilized OMV packaged PTE can be utilized as a cell free reagent for long term environmental remediation of pesticide/chemical warfare contaminated areas.
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18
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Nakayama K, Ishikawa S, Ohmori T, Seto Y, Kawahara K. Immobilization of organophosphorus hydrolase for the degradation of organophosphorus nerve agents. J GEN APPL MICROBIOL 2016; 62:38-41. [PMID: 26923130 DOI: 10.2323/jgam.62.38] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Kosuke Nakayama
- Department of Biosciences, College of Science and Engineering, Kanto Gakuin University
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19
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Nakayama K, Ohmori T, Ishikawa S, Iwata N, Seto Y, Kawahara K. Expression of recombinant organophosphorus hydrolase in the original producer of the enzyme, Sphingobium fuliginis ATCC 27551. Biosci Biotechnol Biochem 2016; 80:1024-6. [PMID: 26784883 DOI: 10.1080/09168451.2015.1123606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The plasmid encoding His-tagged organophosphorus hydrolase (OPH) cloned from Sphingobium fuliginis was modified to be transferred back to this bacterium. The replication function of S. amiense plasmid was inserted at downstream of OPH gene, and S. fuliginis was transformed with this plasmid. The transformant produced larger amount of active OPH with His-tag than E. coli.
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Affiliation(s)
- Kosuke Nakayama
- a Department of Biosciences, College of Science and Engineering , Kanto Gakuin University , Yokohama , Japan
| | - Takeshi Ohmori
- b Third Department of Forensic Science , National Research Institute of Police Science , Kashiwa , Japan
| | - Satoshi Ishikawa
- a Department of Biosciences, College of Science and Engineering , Kanto Gakuin University , Yokohama , Japan
| | - Natsumi Iwata
- a Department of Biosciences, College of Science and Engineering , Kanto Gakuin University , Yokohama , Japan
| | - Yasuo Seto
- b Third Department of Forensic Science , National Research Institute of Police Science , Kashiwa , Japan
| | - Kazuyoshi Kawahara
- b Third Department of Forensic Science , National Research Institute of Police Science , Kashiwa , Japan
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20
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Alves NJ, Turner KB, Daniele MA, Oh E, Medintz IL, Walper SA. Bacterial Nanobioreactors--Directing Enzyme Packaging into Bacterial Outer Membrane Vesicles. ACS APPLIED MATERIALS & INTERFACES 2015; 7:24963-24972. [PMID: 26479678 DOI: 10.1021/acsami.5b08811] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
All bacteria shed outer membrane vesicles (OMVs) loaded with a diverse array of small molecules, proteins, and genetic cargo. In this study we sought to hijack the bacterial cell export pathway to simultaneously produce, package, and release an active enzyme, phosphotriesterase (PTE). To accomplish this goal the SpyCatcher/SpyTag (SC/ST) bioconjugation system was utilized to produce a PTE-SpyCatcher (PTE-SC) fusion protein and a SpyTagged transmembrane porin protein (OmpA-ST), known to be abundant in OMVs. Under a range of physiological conditions the SpyTag and SpyCatcher domains interact with one another and form a covalent isopeptide bond driving packaging of PTE into forming OMVs. The PTE-SC loaded OMVs are characterized for size distribution, number of vesicles produced, cell viability, packaged PTE enzyme kinetics, OMV loading efficiency, and enzyme stability following iterative cycles of freezing and thawing. The PTE-loaded OMVs exhibit native-like enzyme kinetics when assayed with paraoxon as a substrate. PTE is often toxic to expression cultures and has a tendency to lose activity with improper handling. The coexpression of OmpA-ST with PTE-SC, however, greatly improved the overall PTE production levels by mitigating toxicity through exporting of the PTE-SC and greatly enhanced packaged enzyme stability against iterative cycles of freezing and thawing.
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Affiliation(s)
- Nathan J Alves
- National Research Council, 500 Fifth Street NW (Keck 576), Washington, DC 20001, United States
| | | | | | - Eunkeu Oh
- Sotera Defense Solution, Inc. 7230 Lee DeForest Drive, Columbia, Maryland 21046, United States
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21
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Daffu GK, Lopez P, Katz F, Vinogradov M, Zhan CG, Landry DW, Macdonald J. Sulfhydryl-specific PEGylation of phosphotriesterase cysteine mutants for organophosphate detoxification. Protein Eng Des Sel 2015; 28:501-6. [DOI: 10.1093/protein/gzv036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 07/14/2015] [Indexed: 11/13/2022] Open
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22
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Cuquel AC, Dorandeu F, Ceppa F, Renard C, Burnat P. [The VR, the Russian version of the nerve agent VX]. ANNALES PHARMACEUTIQUES FRANÇAISES 2015; 73:180-9. [PMID: 25592653 DOI: 10.1016/j.pharma.2014.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 11/20/2014] [Accepted: 11/21/2014] [Indexed: 10/24/2022]
Abstract
A product of the arms race during the Cold War, the Russian VX, or VR, is an organophosphorus compound that is a structural isomer of the western VX compound (or A4), with which it shares a very high toxicity. It is much less studied and known than VX because the knowledge of its existence is relatively recent. A very low volatility and high resistance in the environment make it a persistent agent. Poisoning occurs mainly following penetration through skin and mucosa but vapour inhalation is a credible risk in some circumstances. The clinical presentation may be differed by several hours and despite the absence of signs and symptoms, the casualty should not be considered as contamination or intoxication-free. This agent has a long residence time in blood, a characteristics that clearly differentiates it from other compounds such as sarin. The protocols for antidote administration may thus have to be changed accordingly. The fact that VR poisoned individuals will less respond to the current oxime therapy used in France, the 2-PAM and that VR represents a higher threat than VX, being probably possessed by some proliferating states, justify the interest for this toxic product.
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Affiliation(s)
- A-C Cuquel
- Fédération de pharmacie-biologie médicale, HIA Val-de-Grâce, 74, boulevard de Port-Royal 75230 Paris cedex, France
| | - F Dorandeu
- Département de toxicologie et risques chimiques, institut de recherche biomédicale des armées, BP 73, 91223 Brétigny-sur-Orge, France
| | - F Ceppa
- Fédération de biologie médicale, hôpital d'instruction des armées Bégin, 94163 Saint-Mandé cedex, France
| | - C Renard
- Fédération de pharmacie-biologie médicale, HIA Val-de-Grâce, 74, boulevard de Port-Royal 75230 Paris cedex, France
| | - P Burnat
- Fédération de biologie médicale, hôpital d'instruction des armées Bégin, 94163 Saint-Mandé cedex, France.
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23
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Post-exposure treatment of VX poisoned guinea pigs with the engineered phosphotriesterase mutant C23: A proof-of-concept study. Toxicol Lett 2014; 231:45-54. [DOI: 10.1016/j.toxlet.2014.09.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/01/2014] [Accepted: 09/03/2014] [Indexed: 11/21/2022]
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24
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Jeong YS, Choi JM, Kyeong HH, Choi JY, Kim EJ, Kim HS. Rational design of organophosphorus hydrolase with high catalytic efficiency for detoxifying a V-type nerve agent. Biochem Biophys Res Commun 2014; 449:263-7. [PMID: 24824182 DOI: 10.1016/j.bbrc.2014.04.155] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 04/29/2014] [Indexed: 11/15/2022]
Abstract
V-type nerve agents, known as VX, are organophosphate (OP) compounds, and show extremely toxic effects on human and animals by causing cholinergic overstimulation of synapses. The bacterial organophosphorus hydrolase (OPH) has attracted much attention for detoxifying V-type agents through hydrolysis of the P-S bond. However, low catalytic efficiency of OPH has limited the practical use of the enzyme. Here we present rational design of OPH with high catalytic efficiency for a V-type nerve agent. Based on the model structure of the enzyme and substrate docking simulation, we predicted the key residues that appear to enhance the access of the substrate to the active site of the enzyme, and constructed numerous OPH mutants. Of them, double mutant, L271/Y309A, was shown to exhibit a 150-fold higher catalytic efficiency for VX than the wild-type.
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Affiliation(s)
- Young-Su Jeong
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Jung Min Choi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Hyun-Ho Kyeong
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | | | | | - Hak-Sung Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
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25
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Nakayama K, Ishikawa S, Kawahara K, Ohmori T, Seto Y. Improvement of organophosphorus hydrolase activity toward nerve agents by amino acid substitutions. Forensic Toxicol 2014. [DOI: 10.1007/s11419-013-0223-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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26
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Cherny I, Greisen P, Ashani Y, Khare SD, Oberdorfer G, Leader H, Baker D, Tawfik DS. Engineering V-type nerve agents detoxifying enzymes using computationally focused libraries. ACS Chem Biol 2013; 8:2394-403. [PMID: 24041203 DOI: 10.1021/cb4004892] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
VX and its Russian (RVX) and Chinese (CVX) analogues rapidly inactivate acetylcholinesterase and are the most toxic stockpile nerve agents. These organophosphates have a thiol leaving group with a choline-like moiety and are hydrolyzed very slowly by natural enzymes. We used an integrated computational and experimental approach to increase Brevundimonas diminuta phosphotriesterase's (PTE) detoxification rate of V-agents by 5000-fold. Computational models were built of the complex between PTE and V-agents. On the basis of these models, the active site was redesigned to be complementary in shape to VX and RVX and to include favorable electrostatic interactions with their choline-like leaving group. Small libraries based on designed sequences were constructed. The libraries were screened by a direct assay for V-agent detoxification, as our initial studies showed that colorimetric surrogates fail to report the detoxification rates of the actual agents. The experimental results were fed back to improve the computational models. Overall, five rounds of iterating between experiment and model refinement led to variants that hydrolyze the toxic SP isomers of all three V-agents with kcat/KM values of up to 5 × 10(6) M(-1) min(-1) and also efficiently detoxify G-agents. These new catalysts provide the basis for broad spectrum nerve agent detoxification.
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Affiliation(s)
- Izhack Cherny
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Per Greisen
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, United States
| | - Yacov Ashani
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sagar D. Khare
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, United States
| | - Gustav Oberdorfer
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, United States
| | - Haim Leader
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, United States
| | - Dan S. Tawfik
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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27
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Oudejans L, Wyrzykowska-Ceradini B, Williams C, Tabor D, Martinez J. Impact of Environmental Conditions on the Enzymatic Decontamination of a Material Surface Contaminated with Chemical Warfare Agent Simulants. Ind Eng Chem Res 2013. [DOI: 10.1021/ie401052z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lukas Oudejans
- National Homeland Security Research Center, Office of Research and Development,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, United States
| | | | - Craig Williams
- ARCADIS US, Inc., Durham, North Carolina
27713, United States
| | - Dennis Tabor
- National Risk Management Research Laboratory, Office of Research and Development,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, United States
| | - Jeanelle Martinez
- Office of Solid Waste and Emergency Response, Office of Emergency Management,
U.S. Environmental Protection Agency, Cincinnati, Ohio 45268, United
States
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28
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Bigley AN, Xu C, Henderson TJ, Harvey SP, Raushel FM. Enzymatic neutralization of the chemical warfare agent VX: evolution of phosphotriesterase for phosphorothiolate hydrolysis. J Am Chem Soc 2013; 135:10426-32. [PMID: 23789980 DOI: 10.1021/ja402832z] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The V-type nerve agents (VX and VR) are among the most toxic substances known. The high toxicity and environmental persistence of VX make the development of novel decontamination methods particularly important. The enzyme phosphotriesterase (PTE) is capable of hydrolyzing VX but with an enzymatic efficiency more than 5 orders of magnitude lower than with its best substrate, paraoxon. PTE has previously proven amenable to directed evolution for the improvement of catalytic activity against selected compounds through the manipulation of active-site residues. Here, a series of sequential two-site mutational libraries encompassing 12 active-site residues of PTE was created. The libraries were screened for catalytic activity against a new VX analogue, DEVX, which contains the same thiolate leaving group of VX coupled to a diethoxyphosphate core rather than the ethoxymethylphosphonate core of VX. The evolved catalytic activity with DEVX was enhanced 26-fold relative to wild-type PTE. Further improvements were facilitated by targeted error-prone PCR mutagenesis of loop-7, and additional PTE variants were identified with up to a 78-fold increase in the rate of DEVX hydrolysis. The best mutant hydrolyzed the racemic nerve agent VX with a value of kcat/Km = 7 × 10(4) M(-1) s(-1), a 230-fold improvement relative to wild-type PTE. The highest turnover number achieved by the mutants created for this investigation was 137 s(-1), an enhancement of 152-fold relative to wild-type PTE. The stereoselectivity for the hydrolysis of the two enantiomers of VX was relatively low. These engineered mutants of PTE are the best catalysts ever reported for the hydrolysis of nerve agent VX.
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Affiliation(s)
- Andrew N Bigley
- Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, Texas 77842, United States
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29
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Effect of dimerization on the catalytic properties of native and chimeric organophosphorus hydrolase determined by molecular modeling of the enzyme structure. Russ Chem Bull 2012. [DOI: 10.1007/s11172-012-0062-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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30
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Mahadevi AS, Sastry GN. Cation-π interaction: its role and relevance in chemistry, biology, and material science. Chem Rev 2012; 113:2100-38. [PMID: 23145968 DOI: 10.1021/cr300222d] [Citation(s) in RCA: 711] [Impact Index Per Article: 59.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- A Subha Mahadevi
- Molecular Modeling Group, CSIR-Indian Institute of Chemical Technology Tarnaka, Hyderabad 500 607, Andhra Pradesh, India
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31
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Bigley AN, Raushel FM. Catalytic mechanisms for phosphotriesterases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1834:443-53. [PMID: 22561533 DOI: 10.1016/j.bbapap.2012.04.004] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 03/31/2012] [Accepted: 04/13/2012] [Indexed: 01/04/2023]
Abstract
Phosphotriesters are one class of highly toxic synthetic compounds known as organophosphates. Wide spread usage of organophosphates as insecticides as well as nerve agents has lead to numerous efforts to identify enzymes capable of detoxifying them. A wide array of enzymes has been found to have phosphotriesterase activity including phosphotriesterase (PTE), methyl parathion hydrolase (MPH), organophosphorus acid anhydrolase (OPAA), diisopropylfluorophosphatase (DFP), and paraoxonase 1 (PON1). These enzymes differ widely in protein sequence and three-dimensional structure, as well as in catalytic mechanism, but they also share several common features. All of the enzymes identified as phosphotriesterases are metal-dependent hydrolases that contain a hydrophobic active site with three discrete binding pockets to accommodate the substrate ester groups. Activation of the substrate phosphorus center is achieved by a direct interaction between the phosphoryl oxygen and a divalent metal in the active site. The mechanistic details of the hydrolytic reaction differ among the various enzymes with both direct attack of a hydroxide as well as covalent catalysis being found. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases.
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Affiliation(s)
- Andrew N Bigley
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, TX 77842-3012, USA
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32
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Wales ME, Reeves TE. Organophosphorus hydrolase as an in vivo catalytic nerve agent bioscavenger. Drug Test Anal 2012; 4:271-81. [DOI: 10.1002/dta.381] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 10/03/2011] [Accepted: 10/03/2011] [Indexed: 11/12/2022]
Affiliation(s)
- Melinda E. Wales
- Department of Biochemistry & Biophysics; Texas A&M University; College Station; TX; USA
| | - Tony E. Reeves
- Southwest Research Institute; Microencapsulation and Nanomaterials, Chemistry and Chemical Engineering Division; San Antonio; TX; USA
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33
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Gomes DEB, Lins RD, Pascutti PG, Lei C, Soares TA. Conformational variability of organophosphorus hydrolase upon soman and paraoxon binding. J Phys Chem B 2011; 115:15389-98. [PMID: 22098575 DOI: 10.1021/jp208787g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The bacterial enzyme organophosphorus hydrolase (OPH) exhibits both catalytic and substrate promiscuity. It hydrolyzes bonds in a variety of phosphotriester (P-O), phosphonothioate (P-S), phosphofluoridate (P-F), and phosphonocyanate (F-CN) compounds. However, its catalytic efficiency varies markedly for different substrates, limiting the broad-range application of OPH as catalyst in the bioremediation of pesticides and chemical war agents. In the present study, pK(a) calculations and multiple explicit-solvent molecular dynamics (MD) simulations were performed to characterize and contrast the structural dynamics of OPH bound to two substrates hydrolyzed with very distinct catalytic efficiencies: the nerve agent soman (O-pinacolylmethylphosphonofluoridate) and the pesticide paraoxon (diethyl p-nitrophenyl phosphate). pK(a) calculations for the substrate-bound and unbound enzyme showed a significant pK(a) shift from standard values (ΔpK(a) = ±3 units) for residues His254 and Arg275. MD simulations of protonated His254 revealed a dynamic hydrogen bond network connecting the catalytic residue Asp301 via His254 to Asp232, Asp233, Arg275, and Asp235, and is consistent with a previously postulated proton relay mechanism to ferry protons away from the active site with substrates that do not require activation of the leaving group. Hydrogen bonds between Asp301 and His254 were persistent in the OPH-paraoxon complex but not in the OPH-soman one, suggesting a potential role for such interaction in the more efficient hydrolysis of paraoxon over soman by OPH. These results are in line with previous mutational studies of residue His254, which led to an increase of the catalytic efficiency of OPH over soman yet decreased its efficiency for paraoxon. In addition, comparative analysis of the molecular trajectories for OPH bound to soman and paraoxon suggests that binding of the latter facilitates the conformational transition of OPH from the open to the closed substate promoting a tighter binding of paraoxon.
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Affiliation(s)
- Diego E B Gomes
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21949-900, Brazil
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34
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Tsai PC, Bigley A, Li Y, Ghanem E, Cadieux CL, Kasten SA, Reeves TE, Cerasoli DM, Raushel FM. Stereoselective hydrolysis of organophosphate nerve agents by the bacterial phosphotriesterase. Biochemistry 2010; 49:7978-87. [PMID: 20701311 DOI: 10.1021/bi101056m] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Organophosphorus compounds include many synthetic, neurotoxic substances that are commonly used as insecticides. The toxicity of these compounds is due to their ability to inhibit the enzyme acetylcholine esterase. Some of the most toxic organophosphates have been adapted for use as chemical warfare agents; the most well-known are GA, GB, GD, GF, VX, and VR. All of these compounds contain a chiral phosphorus center, with the S(P) enantiomers being significantly more toxic than the R(P) enantiomers. Phosphotriesterase (PTE) is an enzyme capable of detoxifying these agents, but the stereochemical preference of the wild-type enzyme is for the R(P) enantiomers. A series of enantiomerically pure chiral nerve agent analogues containing the relevant phosphoryl centers found in GB, GD, GF, VX, and VR has been developed. Wild-type and mutant forms of PTE have been tested for their ability to hydrolyze this series of compounds. Mutant forms of PTE with significantly enhanced, as well as relaxed or reversed, stereoselectivity have been identified. A number of variants exhibited dramatically improved kinetic constants for the catalytic hydrolysis of the more toxic S(P) enantiomers. Improvements of up to 3 orders of magnitude relative to the value of the wild-type enzyme were observed. Some of these mutants were tested against racemic mixtures of GB and GD. The kinetic constants obtained with the chiral nerve agent analogues accurately predict the improved activity and stereoselectivity against the authentic nerve agents used in this study.
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Affiliation(s)
- Ping-Chuan Tsai
- Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, Texas 77842, USA
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35
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Schofield DA, DiNovo AA. Generation of a mutagenized organophosphorus hydrolase for the biodegradation of the organophosphate pesticides malathion and demeton-S. J Appl Microbiol 2010; 109:548-557. [PMID: 20132373 DOI: 10.1111/j.1365-2672.2010.04672.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS The bacterial organophosphorus hydrolase (OPH) enzyme hydrolyses and detoxifies a broad range of toxic organophosphate pesticides and warfare nerve agents by cleaving the various phosphorus-ester bonds (P-O, P-F, P-CN, P-S); however, OPH hydrolyses these bonds with varying efficiencies. The aim of this study was to generate a variant OPH enzyme with improved hydrolytic efficiency against the poorly hydrolysed P-S class of organophosphates. METHODS AND RESULTS The gene encoding OPH was sequentially mutated at specific codons by saturation mutagenesis and screened for improved activity against the P-S substrates demeton-S methyl and malathion. Escherichia coli lysates harbouring the variants displayed up to 177- and 1800-fold improvement in specific activity against demeton-S methyl and malathion, respectively, compared to the wild-type lysates. The specificity constants of the purified variant proteins were improved up to 25-fold for demeton-S methyl and malathion compared to the wild-type. Activity was associated with organophosphate detoxification as the hydrolysed substrate lost the ability to inhibit acetylcholinesterase. The improved hydrolytic efficiency against demeton-S translated to the improved ability to hydrolyse the warfare agent VX. CONCLUSIONS OPH variant enzymes were generated that displayed significantly improved ability to hydrolyse and detoxify organophosphates harbouring the P-S bond. SIGNIFICANCE AND IMPACT OF THE STUDY The long-term goal is to generate an environmentally-friendly enzyme-mediated bioremediation approach for the removal of toxic organophosphate compounds in the environment.
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Affiliation(s)
| | - A A DiNovo
- Guild Associates Inc., Charleston, SC, USA
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36
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Hemmert AC, Otto TC, Wierdl M, Edwards CC, Fleming CD, MacDonald M, Cashman JR, Potter PM, Cerasoli DM, Redinbo MR. Human carboxylesterase 1 stereoselectively binds the nerve agent cyclosarin and spontaneously hydrolyzes the nerve agent sarin. Mol Pharmacol 2010; 77:508-16. [PMID: 20051531 DOI: 10.1124/mol.109.062356] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Organophosphorus (OP) nerve agents are potent toxins that inhibit cholinesterases and produce a rapid and lethal cholinergic crisis. Development of protein-based therapeutics is being pursued with the goal of preventing nerve agent toxicity and protecting against the long-term side effects of these agents. The drug-metabolizing enzyme human carboxylesterase 1 (hCE1) is a candidate protein-based therapeutic because of its similarity in structure and function to the cholinesterase targets of nerve agent poisoning. However, the ability of wild-type hCE1 to process the G-type nerve agents sarin and cyclosarin has not been determined. We report the crystal structure of hCE1 in complex with the nerve agent cyclosarin. We further use stereoselective nerve agent analogs to establish that hCE1 exhibits a 1700- and 2900-fold preference for the P(R) enantiomers of analogs of soman and cyclosarin, respectively, and a 5-fold preference for the P(S) isomer of a sarin analog. Finally, we show that for enzyme inhibited by racemic mixtures of bona fide nerve agents, hCE1 spontaneously reactivates in the presence of sarin but not soman or cyclosarin. The addition of the neutral oxime 2,3-butanedione monoxime increases the rate of reactivation of hCE1 from sarin inhibition by more than 60-fold but has no effect on reactivation with the other agents examined. Taken together, these data demonstrate that hCE1 is only reactivated after inhibition with the more toxic P(S) isomer of sarin. These results provide important insights toward the long-term goal of designing novel forms of hCE1 to act as protein-based therapeutics for nerve agent detoxification.
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Affiliation(s)
- Andrew C Hemmert
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA
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