1
|
McCarver GA, Rajeshkumar T, Vogiatzis KD. Computational catalysis for metal-organic frameworks: An overview. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.213777] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
|
2
|
Jain S, Vanka K. The Effect of Solvent-Substrate Noncovalent Interactions on the Diastereoselectivity in the Intramolecular Carbonyl-Ene and the Staudinger [2 + 2] Cycloaddition Reactions. J Phys Chem A 2020; 124:8019-8028. [PMID: 32894951 DOI: 10.1021/acs.jpca.0c05738] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Noncovalent interactions (NCIs) have been identified as important contributing factors for determining selectivity in organic transformations. However, cases where NCIs between solvents and substrates are responsible for a major extent for determining selectivity are rare. The current computational study with density functional theory identifies two important transformations where this is the case: the intramolecular carbonyl-ene reaction and the Staudinger [2 + 2] cycloaddition reaction. In both cases, the role of explicit solvent molecules interacting noncovalently with the substrate has been taken into account. Calculations indicate that the diastereomeric ratio would be 95.0:5.0 for the formation of tricyclic tetrahydrofuran diastereomers via the intramolecular carbonyl-ene reaction and 94.0:6.0 for the formation of the triflone diastereomers via the Staudinger [2 + 2] cycloaddition reaction, which corroborates with the experiment. Interestingly, in both the cases, the calculations indicate that noninclusion of explicit solvent molecules would lead to only a small difference between the competing transition states, which leads to the conclusion that solvent-substrate NCIs are the major cause for diastereoselectivity in both the cases considered.
Collapse
Affiliation(s)
- Shailja Jain
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Kumar Vanka
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| |
Collapse
|
3
|
de A. Cavalcante SF, Simas ABC, Kuča K. Nerve Agents’ Surrogates: Invaluable Tools for Development of Acetylcholinesterase Reactivators. CURR ORG CHEM 2019. [DOI: 10.2174/1385272823666190806114017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of nerve agents as warfare and in terrorist acts has drawn much attention from the governments and societies. Such toxic organophosphorus compounds are listed in Chemical Weapons Convention as Schedule 1 chemicals. The discussion about the chemical identity of the elusive Novichok agents, more potent compounds than best known G- and V-Agents, which have been implicated in recent rumorous assassination plots, clearly demonstrating the importance of the matter. Furthermore, accidents with pesticides or misuse thereof have been a pressing issue in many countries. In this context, the continued development of novel cholinesterase reactivators, antidotes for organophosphorus poisoning, a rather restricted class of pharmaceutical substances, is warranted. Testing of novel candidates may require use of actual nerve agents. Nonetheless, only a few laboratories comply with the requirements for storing, possession and manipulation of such toxic chemicals. To overcome such limitations, nerve agents’ surrogates may be a useful alternative, as they undergo the same reaction with cholinesterases, yielding similar adducts, allowing assays with novel antidote candidates, among other applications.
Collapse
Affiliation(s)
- Samir F. de A. Cavalcante
- Walter Mors Institute of Research on Natural Products (IPPN), Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Alessandro B. C. Simas
- Walter Mors Institute of Research on Natural Products (IPPN), Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Kamil Kuča
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
| |
Collapse
|
4
|
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: 51] [Impact Index Per Article: 10.2] [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.
Collapse
|
5
|
Brown ME, Mukhopadhyay A, Keasling JD. Engineering Bacteria to Catabolize the Carbonaceous Component of Sarin: Teaching E. coli to Eat Isopropanol. ACS Synth Biol 2016; 5:1485-1496. [PMID: 27403844 DOI: 10.1021/acssynbio.6b00115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report an engineered strain of Escherichia coli that catabolizes the carbonaceous component of the extremely toxic chemical warfare agent sarin. Enzymatic decomposition of sarin generates isopropanol waste that, with this engineered strain, is then transformed into acetyl-CoA by enzymatic conversion with a key reaction performed by the acetone carboxylase complex (ACX). We engineered the heterologous expression of the ACX complex from Xanthobacter autotrophicus PY2 to match the naturally occurring subunit stoichiometry and purified the recombinant complex from E. coli for biochemical analysis. Incorporating this ACX complex and enzymes from diverse organisms, we introduced an isopropanol degradation pathway in E. coli, optimized induction conditions, and decoupled enzyme expression to probe pathway bottlenecks. Our engineered E. coli consumed 65% of isopropanol compared to no-cell controls and was able to grow on isopropanol as a sole carbon source. In the process, reconstitution of this large ACX complex (370 kDa) in a system naïve to its structural and mechanistic requirements allowed us to study this otherwise cryptic enzyme in more detail than would have been possible in the less genetically tractable native Xanthobacter system.
Collapse
Affiliation(s)
- Margaret E. Brown
- Biological
Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Aindrila Mukhopadhyay
- Biological
Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Jay D. Keasling
- Biological
Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Novo
Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Alle, DK2970-Hørsholm, Denmark
| |
Collapse
|
6
|
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]
|
7
|
Abou-Donia MB, Siracuse B, Gupta N, Sobel Sokol A. Sarin (GB, O-isopropyl methylphosphonofluoridate) neurotoxicity: critical review. Crit Rev Toxicol 2016; 46:845-875. [PMID: 27705071 PMCID: PMC5764759 DOI: 10.1080/10408444.2016.1220916] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Sarin (GB, O-isopropyl methylphosphonofluoridate) is a potent organophosphorus (OP) nerve agent that inhibits acetylcholinesterase (AChE) irreversibly. The subsequent build-up of acetylcholine (ACh) in the central nervous system (CNS) provokes seizures and, at sufficient doses, centrally-mediated respiratory arrest. Accumulation of ACh at peripheral autonomic synapses leads to peripheral signs of intoxication and overstimulation of the muscarinic and nicotinic receptors, which is described as "cholinergic crisis" (i.e. diarrhea, sweating, salivation, miosis, bronchoconstriction). Exposure to high doses of sarin can result in tremors, seizures, and hypothermia. More seriously, build-up of ACh at neuromuscular junctions also can cause paralysis and ultimately peripherally-mediated respiratory arrest which can lead to death via respiratory failure. In addition to its primary action on the cholinergic system, sarin possesses other indirect effects. These involve the activation of several neurotransmitters including gamma-amino-butyric acid (GABA) and the alteration of other signaling systems such as ion channels, cell adhesion molecules, and inflammatory regulators. Sarin exposure is associated with symptoms of organophosphate-induced delayed neurotoxicity (OPIDN) and organophosphate-induced chronic neurotoxicity (OPICN). Moreover, sarin has been involved in toxic and immunotoxic effects as well as organophosphate-induced endocrine disruption (OPIED). The standard treatment for sarin-like nerve agent exposure is post-exposure injection of atropine, a muscarinic receptor antagonist, accompanied by an oxime, an AChE reactivator, and diazepam.
Collapse
Affiliation(s)
- Mohamed B Abou-Donia
- a Department of Pharmacology and Cancer Biology , Duke University , Durham , NC , USA
| | - Briana Siracuse
- a Department of Pharmacology and Cancer Biology , Duke University , Durham , NC , USA
| | - Natasha Gupta
- a Department of Pharmacology and Cancer Biology , Duke University , Durham , NC , USA
| | - Ashly Sobel Sokol
- a Department of Pharmacology and Cancer Biology , Duke University , Durham , NC , USA
| |
Collapse
|
8
|
Gorecki L, Korabecny J, Musilek K, Malinak D, Nepovimova E, Dolezal R, Jun D, Soukup O, Kuca K. SAR study to find optimal cholinesterase reactivator against organophosphorous nerve agents and pesticides. Arch Toxicol 2016; 90:2831-2859. [PMID: 27582056 DOI: 10.1007/s00204-016-1827-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 08/22/2016] [Indexed: 01/13/2023]
Abstract
Irreversible inhibition of acetylcholinesterase (AChE) by organophosphates leads to many failures in living organism and ultimately in death. Organophosphorus compounds developed as nerve agents such as tabun, sarin, soman, VX and others belong to the most toxic chemical warfare agents and are one of the biggest threats to the modern civilization. Moreover, misuse of nerve agents together with organophosphorus pesticides (e.g. malathion, paraoxon, chlorpyrifos, etc.) which are annually implicated in millions of intoxications and hundreds of thousand deaths reminds us of insufficient protection against these compounds. Basic treatments for these intoxications are based on immediate administration of atropine and acetylcholinesterase reactivators which are currently represented by mono- or bis-pyridinium aldoximes. However, these antidotes are not sufficient to ensure 100 % treatment efficacy even they are administered immediately after intoxication, and in general, they possess several drawbacks. Herein, we have reviewed new efforts leading to the development of novel reactivators and proposition of new promising strategies to design novel and effective antidotes. Structure-activity relationships and biological activities of recently proposed acetylcholinesterase reactivators are discussed and summarized. Among further modifications of known oximes, the main attention has been paid to dual binding site ligands of AChE as the current mainstream strategy. We have also discussed new chemical entities as potential replacement of oxime functional group.
Collapse
Affiliation(s)
- Lukas Gorecki
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Jan Korabecny
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Kamil Musilek
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic.,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic
| | - David Malinak
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Physiology and Pathophysiology, Faculty of Medicine, University of Ostrava, Syllabova 19, 703 00, Ostrava, Czech Republic
| | - Eugenie Nepovimova
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Rafael Dolezal
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic
| | - Daniel Jun
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Ondrej Soukup
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Kamil Kuca
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic. .,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic.
| |
Collapse
|
9
|
Lyagin IV, Andrianova MS, Efremenko EN. Extensive hydrolysis of phosphonates as unexpected behaviour of the known His6-organophosphorus hydrolase. Appl Microbiol Biotechnol 2016; 100:5829-38. [PMID: 26932546 DOI: 10.1007/s00253-016-7407-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/10/2016] [Accepted: 02/19/2016] [Indexed: 10/22/2022]
Abstract
The catalytic activity of hexahistidine-tagged organophosphorus hydrolase (His6-OPH) in hydrolytic reactions of methylphosphonic acid (MPA) and its monoesters and diesters being decomposition products of R-VX was demonstrated for the first time. The catalytic constants of enzyme in such reactions were determined. The mechanism of C-P bond cleavage in the MPA by His6-OPH was proposed. Such reaction was estimated to be carried out with the soluble and nanocapsulated forms of His6-OPH. His6-OPH was demonstrated to be capable of degrading the key organophosphorus components of reaction masses (RMs) that are produced by the chemical detoxification of R-VX and RMs are multi-substrate mixtures for this enzyme. The kinetic model describing the behaviour of His6-OPH in RMs was proposed and was shown to adequately fit experimental points during degradation of the real samples of RMs.
Collapse
Affiliation(s)
- Ilya V Lyagin
- Chemistry Department, Lomonosov Moscow State University, Lenin Hills, 1, building 3, Moscow, 119991, Russia.,Institute of Biochemical Physics RAS, Kosygin St. 4, Moscow, 119334, Russia
| | - Mariia S Andrianova
- SMC Technological Center MIET, Proezd No. 4806, 5, Moscow, Zelenograd, 124498, Russia
| | - Elena N Efremenko
- Chemistry Department, Lomonosov Moscow State University, Lenin Hills, 1, building 3, Moscow, 119991, Russia. .,Institute of Biochemical Physics RAS, Kosygin St. 4, Moscow, 119334, Russia.
| |
Collapse
|
10
|
Katz FS, Pecic S, Tran TH, Trakht I, Schneider L, Zhu Z, Ton-That L, Luzac M, Zlatanic V, Damera S, Macdonald J, Landry DW, Tong L, Stojanovic MN. Discovery of New Classes of Compounds that Reactivate Acetylcholinesterase Inhibited by Organophosphates. Chembiochem 2015; 16:2205-2215. [PMID: 26350723 DOI: 10.1002/cbic.201500348] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Indexed: 11/11/2022]
Abstract
Acetylcholinesterase (AChE) that has been covalently inhibited by organophosphate compounds (OPCs), such as nerve agents and pesticides, has traditionally been reactivated by using nucleophilic oximes. There is, however, a clearly recognized need for new classes of compounds with the ability to reactivate inhibited AChE with improved in vivo efficacy. Here we describe our discovery of new functional groups--Mannich phenols and general bases--that are capable of reactivating OPC--inhibited AChE more efficiently than standard oximes and we describe the cooperative mechanism by which these functionalities are delivered to the active site. These discoveries, supported by preliminary in vivo results and crystallographic data, significantly broaden the available approaches for reactivation of AChE.
Collapse
Affiliation(s)
- Francine S Katz
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Stevan Pecic
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Timothy H Tran
- Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, New York, NY 10027 (USA)
| | - Ilya Trakht
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Laura Schneider
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Zhengxiang Zhu
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Long Ton-That
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Michal Luzac
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Viktor Zlatanic
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Shivani Damera
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Joanne Macdonald
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA).,Genecology Research Centre, Inflammation and Healing Research Cluster, School of Science and Engineering, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, QLD 4556 (Australia)
| | - Donald W Landry
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA)
| | - Liang Tong
- Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, New York, NY 10027 (USA)
| | - Milan N Stojanovic
- Department of Medicine/Division of Experimental Therapeutics, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032 (USA).,Departments of Biomedical Engineering and Systems Biology, Columbia University, 630 W. 168th street, New York, NY 10032 (USA)
| |
Collapse
|
11
|
|
12
|
Tsai PC, Fox N, Bigley AN, Harvey SP, Barondeau DP, Raushel FM. Enzymes for the homeland defense: optimizing phosphotriesterase for the hydrolysis of organophosphate nerve agents. Biochemistry 2012; 51:6463-75. [PMID: 22809162 DOI: 10.1021/bi300811t] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphotriesterase (PTE) from soil bacteria is known for its ability to catalyze the detoxification of organophosphate pesticides and chemical warfare agents. Most of the organophosphate chemical warfare agents are a mixture of two stereoisomers at the phosphorus center, and the S(P)-enantiomers are significantly more toxic than the R(P)-enantiomers. In previous investigations, PTE variants were created through the manipulation of the substrate binding pockets and these mutants were shown to have greater catalytic activities for the detoxification of the more toxic S(P)-enantiomers of nerve agent analogues for GB, GD, GF, VX, and VR than the less toxic R(P)-enantiomers. In this investigation, alternate strategies were employed to discover additional PTE variants with significant improvements in catalytic activities relative to that of the wild-type enzyme. Screening and selection techniques were utilized to isolate PTE variants from randomized libraries and site specific modifications. The catalytic activities of these newly identified PTE variants toward the S(P)-enantiomers of chromophoric analogues of GB, GD, GF, VX, and VR have been improved up to 15000-fold relative to that of the wild-type enzyme. The X-ray crystal structures of the best PTE variants were determined. Characterization of these mutants with the authentic G-type nerve agents has confirmed the expected improvements in catalytic activity against the most toxic enantiomers of GB, GD, and GF. The values of k(cat)/K(m) for the H257Y/L303T (YT) mutant for the hydrolysis of GB, GD, and GF were determined to be 2 × 10(6), 5 × 10(5), and 8 × 10(5) M(-1) s(-1), respectively. The YT mutant is the most proficient enzyme reported thus far for the detoxification of G-type nerve agents. These results support a combinatorial strategy of rational design and directed evolution as a powerful tool for the discovery of more efficient enzymes for the detoxification of organophosphate nerve agents.
Collapse
Affiliation(s)
- Ping-Chuan Tsai
- Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, TX 77842, USA
| | | | | | | | | | | |
Collapse
|
13
|
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: 153] [Impact Index Per Article: 12.8] [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.
Collapse
Affiliation(s)
- Andrew N Bigley
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, TX 77842-3012, USA
| | | |
Collapse
|
14
|
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.
Collapse
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
| | | | | | | | | |
Collapse
|
15
|
Trovaslet-Leroy M, Musilova L, Renault F, Brazzolotto X, Misik J, Novotny L, Froment MT, Gillon E, Loiodice M, Verdier L, Masson P, Rochu D, Jun D, Nachon F. Organophosphate hydrolases as catalytic bioscavengers of organophosphorus nerve agents. Toxicol Lett 2011; 206:14-23. [PMID: 21683774 DOI: 10.1016/j.toxlet.2011.05.1041] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 05/27/2011] [Accepted: 05/31/2011] [Indexed: 01/30/2023]
Abstract
Bioscavengers are molecules able to neutralize neurotoxic organophosphorus compounds (OP) before they can reach their biological target. Human butyrylcholinesterase (hBChE) is a natural bioscavenger each molecule of enzyme neutralizing one molecule of OP. The amount of natural enzyme is insufficient to achieve good protection. Thus, different strategies have been envisioned. The most straightforward consists in injecting a large dose of highly purified natural hBChE to increase the amount of bioscavenger in the bloodstream. This proved to be successful for protection against lethal doses of soman and VX but remains expensive. An improved strategy is to regenerate prophylactic cholinesterases (ChE) by administration of reactivators after exposure. But broad-spectrum efficient reactivators are still lacking, especially for inhibited hBChE. Cholinesterase mutants capable of reactivating spontaneously are another option. The G117H hBChE mutant has been a prototype. We present here the Y124H/Y72D mutant of human acetylcholinesterase; its spontaneous reactivation rate after V-agent inhibition is increased up to 110 fold. Catalytic bioscavengers, enzymes capable of hydrolyzing OP, present the best alternative. Mesophilic bacterial phosphotriesterase (PTE) is a candidate with good catalytic efficiency. Its enantioselectivity has been enhanced against the most potent OP isomers by rational design. We show that PEGylation of this enzyme improves its mean residence time in the rat blood stream 24-fold and its bioavailability 120-fold. Immunogenic issues remain to be solved. Human paraoxonase 1 (hPON1) is another promising candidate. However, its main drawback is that its phosphotriesterase activity is highly dependent on its environment. Recent progress has been made using a mammalian chimera of PON1, but we provide here additional data showing that this chimera is biochemically different from hPON1. Besides, the chimera is expected to suffer from immunogenic issues. Thus, we stress that interest for hPON1 must not fade away, and in particular, the 3D structure of the hPON1 eventually in complex with OP has to be solved.
Collapse
Affiliation(s)
- Marie Trovaslet-Leroy
- Département de Toxicologie, Institut de Recherches Biomédicales des Armées, 38700 La Tronche, France
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Gupta RD, Goldsmith M, Ashani Y, Simo Y, Mullokandov G, Bar H, Ben-David M, Leader H, Margalit R, Silman I, Sussman JL, Tawfik DS. Directed evolution of hydrolases for prevention of G-type nerve agent intoxication. Nat Chem Biol 2011; 7:120-5. [DOI: 10.1038/nchembio.510] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 11/22/2010] [Indexed: 11/09/2022]
|
17
|
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.
Collapse
Affiliation(s)
- Ping-Chuan Tsai
- Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, Texas 77842, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Tsai PC, Fan Y, Kim J, Yang L, Almo SC, Gao YQ, Raushel FM. Structural determinants for the stereoselective hydrolysis of chiral substrates by phosphotriesterase. Biochemistry 2010; 49:7988-97. [PMID: 20695627 DOI: 10.1021/bi101058z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Wild-type phosphotriesterase (PTE) preferentially hydrolyzes the R(P) enantiomers of the nerve agents sarin (GB) and cyclosarin (GF) and their chromophoric analogues. The active site of PTE can be subdivided into three binding pockets that have been denoted as the small, large, and leaving group pockets based on high-resolution crystal structures. The sizes and shapes of these pockets dictate the substrate specificity and stereoselectivity for catalysis. Mutants of PTE that exhibit substantial changes in substrate specificity and the ability to differentiate between chiral substrates have been prepared. For example, the G60A mutant is stereoselective for the hydrolysis of the R(P) enantiomer of the chromophoric analogues of sarin and cyclosarin, whereas the H254G/H257W/L303T (GWT) mutant reverses the stereoselectivity for the enantiomers of these two compounds. Molecular dynamics simulations and high-resolution X-ray structures identified the correlations between structural changes in the active site and the experimentally determined kinetic parameters for substrate hydrolysis. New high-resolution structures were determined for the H257Y/L303T (YT), I106G/F132G/H257Y (GGY), and H254Q/H257F (QF) mutants of PTE. Molecular dynamics calculations were conducted using the S(P) and R(P) enantiomers of the analogues for sarin and cyclosarin for the wild-type PTE and the G60A, YT, GGY, QF, and GWT mutants. The experimental stereoselectivity correlated nicely with the difference in the computed angle of attack for the nucleophilic hydroxide relative to the phenolic leaving group of the substrate.
Collapse
Affiliation(s)
- Ping-Chuan Tsai
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA
| | | | | | | | | | | | | |
Collapse
|
19
|
Mutation of outer-shell residues modulates metal ion co-ordination strength in a metalloenzyme. Biochem J 2010; 429:313-21. [DOI: 10.1042/bj20100233] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The metal ion co-ordination sites of many metalloproteins have been characterized by a variety of spectroscopic techniques and small-molecule model systems, revealing many important insights into the structural determinants of metal ion co-ordination. However, our understanding of this fundamentally and practically important phenomenon remains frustratingly simplistic; in many proteins it is essentially impossible to predict metal ion specificity and the effects of remote ‘outer-shell’ residues on metal ion co-ordination strength are also poorly defined. This is exemplified by our inability to explain why metalloenzymes with identical metal ion co-ordination spheres, such as the closely related orthologues of bacterial PTE (phosphotriesterase) from Agrobacterium radiobacter and Pseudomonas diminuta, display different metal ion specificity and co-ordination strength. In the present study, we present a series of PTE variants that all possess identical metal ion co-ordination spheres, yet display large differences in their metal ion co-ordination strength. Using measurement of the rates of metal ion dissociation from the active site alongside analysis of structural data obtained through X-ray crystallography, we show that ‘outer-shell’ residues provide essential support for the metal ion ligands, in effect buttressing them in their optimal orientation. Remote mutations appear to modulate metal ion interactions by increasing or decreasing the stabilizing effects of these networks. The present study therefore provides a description of how the greater protein fold can be modified to ‘tune’ the strength of metal ion co-ordination and metal ion specificity, as well as reinforcing the concept of proteins as ensembles of conformational states with unique structures and biochemical properties.
Collapse
|
20
|
Ashani Y, Gupta RD, Goldsmith M, Silman I, Sussman JL, Tawfik DS, Leader H. Stereo-specific synthesis of analogs of nerve agents and their utilization for selection and characterization of paraoxonase (PON1) catalytic scavengers. Chem Biol Interact 2010; 187:362-9. [PMID: 20303930 DOI: 10.1016/j.cbi.2010.02.039] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 02/11/2010] [Accepted: 02/23/2010] [Indexed: 10/19/2022]
Abstract
Fluorogenic organophosphate inhibitors of acetylcholinesterase (AChE) homologous in structure to nerve agents provide useful probes for high throughput screening of mammalian paraoxonase (PON1) libraries generated by directed evolution of an engineered PON1 variant with wild-type like specificity (rePON1). Wt PON1 and rePON1 hydrolyze preferentially the less-toxic R(P) enantiomers of nerve agents and of their fluorogenic surrogates containing the fluorescent leaving group, 3-cyano-7-hydroxy-4-methylcoumarin (CHMC). To increase the sensitivity and reliability of the screening protocol so as to directly select rePON1 clones displaying stereo-preference towards the toxic S(P) enantiomer, and to determine accurately K(m) and k(cat) values for the individual isomers, two approaches were used to obtain the corresponding S(P) and R(P) isomers: (a) stereo-specific synthesis of the O-ethyl, O-n-propyl, and O-i-propyl analogs and (b) enzymic resolution of a racemic mixture of O-cyclohexyl methylphosphonylated CHMC. The configurational assignments of the S(P) and R(P) isomers, as well as their optical purity, were established by X-ray diffraction, reaction with sodium fluoride, hydrolysis by selected rePON1 variants, and inhibition of AChE. The S(P) configuration of the tested surrogates was established for the enantiomer with the more potent anti-AChE activity, with S(P)/R(P) inhibition ratios of 10-100, whereas the R(P) isomers of the O-ethyl and O-n-propyl were hydrolyzed by wt rePON1 about 600- and 70-fold faster, respectively, than the S(P) counterpart. Wt rePON1-induced R(P)/S(P) hydrolysis ratios for the O-cyclohexyl and O-i-propyl analogs are estimated to be >>1000. The various S(P) enantiomers of O-alkyl-methylphosphonyl esters of CHMC provide suitable ligands for screening rePON1 libraries, and can expedite identification of variants with enhanced catalytic proficiency towards the toxic nerve agents.
Collapse
Affiliation(s)
- Y Ashani
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | | | | | | | | | | |
Collapse
|
21
|
Gilley C, MacDonald M, Nachon F, Schopfer LM, Zhang J, Cashman JR, Lockridge O. Nerve agent analogues that produce authentic soman, sarin, tabun, and cyclohexyl methylphosphonate-modified human butyrylcholinesterase. Chem Res Toxicol 2010; 22:1680-8. [PMID: 19715348 DOI: 10.1021/tx900090m] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The goal was to test 14 nerve agent model compounds of soman, sarin, tabun, and cyclohexyl methylphosphonofluoridate (GF) for their suitability as substitutes for true nerve agents. We wanted to know whether the model compounds would form the identical covalent adduct with human butyrylcholinesterase that is produced by reaction with true nerve agents. Nerve agent model compounds containing thiocholine or thiomethyl in place of fluorine or cyanide were synthesized as Sp and Rp stereoisomers. Purified human butyrylcholinesterase was treated with a 45-fold molar excess of nerve agent analogue at pH 7.4 for 17 h at 21 degrees C. The protein was denatured by boiling and was digested with trypsin. Aged and nonaged active site peptide adducts were quantified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry of the tryptic digest mixture. The active site peptides were isolated by HPLC and analyzed by MALDI-TOF-TOF mass spectrometry. Serine 198 of butyrylcholinesterase was covalently modified by all 14 compounds. Thiocholine was the leaving group in all compounds that had thiocholine in place of fluorine or cyanide. Thiomethyl was the leaving group in the GF thiomethyl compounds. However, sarin thiomethyl compounds released either thiomethyl or isopropyl, while soman thiomethyl compounds released either thiomethyl or pinacolyl. Thiocholine compounds reacted more rapidly with butyrylcholinesterase than thiomethyl compounds. Labeling with the model compounds resulted in aged adducts that had lost the O-alkyl group (O-ethyl for tabun, O-cyclohexyl for GF, isopropyl for sarin, and pinacolyl for soman) in addition to the thiocholine or thiomethyl group. The nerve agent model compounds containing thiocholine and the GF thiomethyl analogue were found to be suitable substitutes for true soman, sarin, tabun, and GF in terms of the adduct that they produced with human butyrylcholinesterase. However, the soman and sarin thiomethyl compounds yielded two types of adducts, one of which was thiomethyl phosphonate, a modification not found after treatment with authentic soman and sarin.
Collapse
Affiliation(s)
- Cynthia Gilley
- Human BioMolecular Research Institute, San Diego, California 92121, USA
| | | | | | | | | | | | | |
Collapse
|
22
|
Barakat NH, Zheng X, Gilley CB, MacDonald M, Okolotowicz K, Cashman JR, Vyas S, Beck JM, Hadad CM, Zhang J. Chemical synthesis of two series of nerve agent model compounds and their stereoselective interaction with human acetylcholinesterase and human butyrylcholinesterase. Chem Res Toxicol 2010; 22:1669-79. [PMID: 19715346 DOI: 10.1021/tx900096j] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Both G and V type nerve agents possess a center of chirality about phosphorus. The S(p) enantiomers are generally more potent inhibitors than their R(p) counterparts toward acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). To develop model compounds with defined centers of chirality that mimic the target nerve agent structures, we synthesized both the S(p) and the R(p) stereoisomers of two series of G type nerve agent model compounds in enantiomerically enriched form. The two series of model compounds contained identical substituents on the phosphorus as the G type agents, except that thiomethyl (CH(3)-S-) and thiocholine [(CH(3))(3)NCH(2)CH(2)-S-] groups were used to replace the traditional nerve agent leaving groups (i.e., fluoro for GB, GF, and GD and cyano for GA). Inhibition kinetic studies of the thiomethyl- and thiocholine-substituted series of nerve agent model compounds revealed that the S(p) enantiomers of both series of compounds showed greater inhibition potency toward AChE and BChE. The level of stereoselectivity, as indicated by the ratio of the bimolecular inhibition rate constants between S(p) and R(p) enantiomers, was greatest for the GF model compounds in both series. The thiocholine analogues were much more potent than the corresponding thiomethyl analogues. With the exception of the GA model compounds, both series showed greater potency against AChE than BChE. The stereoselectivity (i.e., S(p) > R(p)), enzyme selectivity, and dynamic range of inhibition potency contributed from these two series of compounds suggest that the combined application of these model compounds will provide useful research tools for understanding interactions of nerve agents with cholinesterase and other enzymes involved in nerve agent and organophosphate pharmacology. The potential of and limitations for using these model compounds in the development of biological therapeutics against nerve agent toxicity are also discussed.
Collapse
Affiliation(s)
- Nora H Barakat
- Human BioMolecular Research Institute, San Diego, California 92121, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Gomes DE, Lins RD, Pascutti PG, Lei C, Soares TA. The role of nonbonded interactions in the conformational dynamics of organophosphorous hydrolase adsorbed onto functionalized mesoporous silica surfaces. J Phys Chem B 2010; 114:531-40. [PMID: 19938866 PMCID: PMC2818561 DOI: 10.1021/jp9083635] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The enzyme organophosphorous hydrolase (OPH) catalyzes the hydrolysis of a wide variety of organophosphorous compounds with high catalytic efficiency and broad substrate specificity. The immobilization of OPH in functionalized mesoporous silica (FMS) surfaces increases significantly its catalytic specific activity, as compared to the enzyme in solution, with important applications for the detection and decontamination of insecticides and chemical warfare agents. Experimental measurements of immobilization efficiency as a function of the charge and coverage percentage of different functional groups have been interpreted as electrostatic forces being the predominant interactions underlying the adsorption of OPH onto FMS surfaces. Explicit solvent molecular dynamics simulations have been performed for OPH in bulk solution and adsorbed onto two distinct interaction potential models of the FMS functional groups to investigate the relative contributions of nonbonded interactions to the conformational dynamics and adsorption of the protein. Our results support the conclusion that electrostatic interactions are responsible for the binding of OPH to the FMS surface. However, these results also show that van der Waals forces are detrimental for interfacial adhesion. In addition, it is found that OPH adsorption onto the FMS models favors a protein conformation whose active site is fully accessible to the substrate, in contrast to the unconfined protein.
Collapse
Affiliation(s)
- Diego E.B. Gomes
- Pacific Northwest National Laboratory, P.O. Box 999, MSIN K7-90, Richland, WA 99352, USA
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21949-900, Brazil
| | - Roberto D. Lins
- Pacific Northwest National Laboratory, P.O. Box 999, MSIN K7-90, Richland, WA 99352, USA
- Departamento de Química Fundamental, CCEN, UFPE, 50590-470, Recife PE, Brazil
| | - Pedro G. Pascutti
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21949-900, Brazil
| | - Chenghong Lei
- Pacific Northwest National Laboratory, P.O. Box 999, MSIN K7-90, Richland, WA 99352, USA
| | - Thereza A. Soares
- Pacific Northwest National Laboratory, P.O. Box 999, MSIN K7-90, Richland, WA 99352, USA
- Departamento de Química Fundamental, CCEN, UFPE, 50590-470, Recife PE, Brazil
| |
Collapse
|
24
|
Kwasnieski O, Verdier L, Malacria M, Derat E. Fixation of the two Tabun isomers in acetylcholinesterase: a QM/MM study. J Phys Chem B 2009; 113:10001-7. [PMID: 19569635 DOI: 10.1021/jp903843s] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Dysfunction of acetylcholinesterase (AChE) due to inhibition by organophosphorus (OP) compounds is a major threat since AChE is a key enzyme in neurotransmission. To more rigorously design reactivation agents, it is of prime importance to understand the mechanism of inhibition of AChE by OP compounds. Tabun is one of the more potent nerve agents. It is produced as a mixture of two enantiomers, one of them (the levorotatory isomer) being 6.3 times more potent. Could it be that the inhibition mechanism is different for the two enantiomers? To address this critical issue, we used a hybrid quantum mechanics/molecular mechanics (QM/MM) methodology. Calculations were performed using BP86 functional and TZVP basis set. Single points were also done with B3LYP and PBE0 functionals. We studied the four possible attacks of tabun on the oxygen of Ser203 using two crystallographic structures (PDB codes 2C0P and 3DL7): (S) tabun with the cyano group syn to the oxygen of Ser203 and (R) tabun with the cyano group anti, corresponding to the experimental X-ray structure; (S) tabun with the cyano group anti to the oxygen of Ser203 and (R) tabun with the cyano group syn, leading to a different isomer than was experimentally seen. We found that the most active enantiomer is (S) tabun with the cyano group syn to the oxygen of Ser203. Thus it seems that the cyano group does not leave anti to the oxygen of Ser203 due to repulsive polar interactions between cyanide and aromatic residues in the active site.
Collapse
Affiliation(s)
- Ophélie Kwasnieski
- Institut de chimie moléculaire, UMR CNRS 7201, UPMC University Paris 06, C. 229, 4 place Jussieu, 75005 Paris, France
| | | | | | | |
Collapse
|
25
|
Jokanović M. Current understanding of the mechanisms involved in metabolic detoxification of warfare nerve agents. Toxicol Lett 2009; 188:1-10. [DOI: 10.1016/j.toxlet.2009.03.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 03/17/2009] [Accepted: 03/23/2009] [Indexed: 11/25/2022]
|
26
|
Amitai G, Adani R, Limanovich O, Teitlboim S, Yishay S, Tveria L, Yacov G, Meshulam H, Raveh L. Characterization of asymmetric fluorogenic phosphonates as probes for developing organophosphorus hydrolases with broader stereoselectivity. Chem Biol Interact 2008; 175:249-54. [PMID: 18588863 DOI: 10.1016/j.cbi.2008.05.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Revised: 05/14/2008] [Accepted: 05/15/2008] [Indexed: 11/18/2022]
Abstract
Organophosphorus hydrolases (OPH) such as mammalian plama paraoxonase (PON1) detoxify asymmetric toxic organophosphorus (OP) nerve agents by preferentially hydrolyzing the less toxic P(+) optical isomer. In order to develop new OPHs with broader stereoselectivity we have prepared a series of asymmetric fluorogenic organophosphonates (Flu-OPs). Such Flu-OPs may serve as molecular probes for screening large libraries of OP hydrolases during directed evolution. Flu-OPs were prepared as methylphosphonates (MPs) diesters containing either ethyl (E), isopropyl (I), cyclohexyl (C) or pinacolyl (P) groups that are structural congeners of the nerve agents VX, sarin, cyclosarin and soman, respectively. The second ester bond was formed with fluorescent moieties that are either 3-cyano-4-methyl-7-hydroxy coumarin (MeCyC) or 1,3-dichloro-7-hydroxy 9,9-dimethyl-9H-acridin-2-one (DDAO). To further characterize the Flu-OPs as surrogates of their respective nerve agents, we have studied the reactivation of Flu-OP-inhibited AChE using 2-PAM and toxogonin (TOX). AChE was 90-95% inhibited by all Flu-OPs (0.36-0.9(M) and then was reactivated by either 2-PAM or TOX. TOX caused a more rapid reactivation than 2-PAM with the following rank order; EMP>IMP>CMP. TOX was also shown to be a better reactivator than 2-PAM for AChE inhibited by the nerve agents VX and cyclosarin. PMP-AChE could not be reactivated by either TOX or 2-PAM, similarly to aging of PMP-AChE formed by inhibition with soman. Racemic CMP-MeCyC was used for screening two new PON1 variants from a neutral library of PON1. These multiple mutation variants include replacement of active site amino acid residues. Neither mutation in these new variants appeared in PON1 variants previously discovered by directed evolution using symmetric Flu-OP. Detoxification rate of cylcosarin by these new PON1 variants was rather slow indicating the need to further screen PON1 clones using optically active Flu-OPs. Therefore, we have separated enzymatically the P(-) enantiomer of CMP-MeCyC and determined its 98% purity using chiral HPLC.
Collapse
Affiliation(s)
- G Amitai
- Department of Medicinal Chemistry, Israel Institute for Biological Research, Ness Ziona, Israel
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Chen SL, Fang WH, Himo F. Technical aspects of quantum chemical modeling of enzymatic reactions: the case of phosphotriesterase. Theor Chem Acc 2008. [DOI: 10.1007/s00214-008-0430-y] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
28
|
Differentiation of chiral phosphorus enantiomers by P and H NMR spectroscopy using amino acid derivatives as chemical solvating agents. ACTA ACUST UNITED AC 2007; 18:1391-1397. [PMID: 18037983 DOI: 10.1016/j.tetasy.2007.06.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ability of commercially available amino acid derivatives, especially Fmoc-Trp(Boc)-OH, to differentiate enantiomers of chiral phosphonates, phosphinates, phosphates, phosphine oxides, and phosphonamidates is demonstrated with (31)P, (13)C, and (1)H NMR spectroscopy. The chiral differentiation provided a rapid and convenient method for measuring the enantiomeric purity of these phosphorus compounds.
Collapse
|
29
|
Yeung DT, Smith JR, Sweeney RE, Lenz DE, Cerasoli DM. Direct detection of stereospecific soman hydrolysis by wild-type human serum paraoxonase. FEBS J 2007; 274:1183-91. [PMID: 17286579 DOI: 10.1111/j.1742-4658.2006.05650.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human serum paraoxonase 1 (HuPON1; EC 3.1.8.1) is a calcium-dependent six-fold beta-propeller enzyme that has been shown to hydrolyze an array of substrates, including organophosphorus (OP) chemical warfare nerve agents. Although recent efforts utilizing site-directed mutagenesis have demonstrated specific residues (such as Phe222 and His115) to be important in determining the specificity of OP substrate binding and hydrolysis, little effort has focused on the substrate stereospecificity of the enzyme; different stereoisomers of OPs can differ in their toxicity by several orders of magnitude. For example, the C+/-P- isomers of the chemical warfare agent soman (GD) are known to be more toxic by three orders of magnitude. In this study, the catalytic activity of HuPON1 towards each of the four chiral isomers of GD was measured simultaneously via chiral GC/MS. The catalytic efficiency (k(cat)/K(m)) of the wild-type enzyme for the various stereoisomers was determined by a simultaneous solution of hydrolysis kinetics for each isomer. Derived k(cat)/K(m) values ranged from 625 to 4130 mm(-1).min(-1), with isomers being hydrolyzed in the order of preference C+P+ > C-P+ > C+P- > C-P-. The results indicate that HuPON1 hydrolysis of GD is stereoselective; substrate stereospecificity should be considered in future efforts to enhance the OPase activity of this and other candidate bioscavenger enzymes.
Collapse
Affiliation(s)
- David T Yeung
- Physiology and Immunology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, USA
| | | | | | | | | |
Collapse
|
30
|
Chen SL, Fang WH, Himo F. Theoretical study of the phosphotriesterase reaction mechanism. J Phys Chem B 2007; 111:1253-5. [PMID: 17253743 DOI: 10.1021/jp068500n] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphotriesterase (PTE) is a binuclear zinc enzyme that catalyzes the hydrolysis of extremely toxic organophosphate triesters. In the present work, we have investigated the reaction mechanism of PTE using the hybrid density functional theory method B3LYP. We present a potential energy surface for the reaction and provide characterization of the transition states and intermediates. We used the high resolution crystal structure to construct a model of the active site of PTE, containing the two zinc ions and their first shell ligands. The calculations provide strong support to an associative mechanism for the hydrolysis of phosphotriesters by PTE. No protonation of the leaving group was found to be necessary. In particular, the calculations demonstrate that the nucleophilicity of the bridging hydroxide is sufficient to be utilized in the hydrolysis reaction, a feature that is of importance for a number of other di-zinc enzymes.
Collapse
|
31
|
Amitai G, Adani R, Yacov G, Yishay S, Teitlboim S, Tveria L, Limanovich O, Kushnir M, Meshulam H. Asymmetric fluorogenic organophosphates for the development of active organophosphate hydrolases with reversed stereoselectivity. Toxicology 2006; 233:187-98. [PMID: 17129656 DOI: 10.1016/j.tox.2006.09.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 08/28/2006] [Accepted: 09/25/2006] [Indexed: 10/23/2022]
Abstract
In order to enhance the enzymatic detoxification rate of organophosphorus (OP) nerve agents we have searched for more active variants of recombinant mammalian paraoxonase (PON1). We have previously identified three key positions in PON1 that affect OP hydrolysis: Leu69, Val346 and His115, that significantly enhance the hydrolysis of cyclosarin (GF), soman, chlorpyrifos-oxon (ChPo), O-isopropyl-O-(p-nitrophenyl)methylphosphonate (IMP-pNP) and diisopropyl fluorophosphate (DFP). GC/FPD analysis compared to residual AChE inhibition assay displayed stereoselective hydrolysis of GF, soman and IMP-pNP, indicating that wild type PON1 and its variant V346A are more active toward the less toxic P(+) optical isomer. In order to obtain new PON1 variants with reversed stereoselectivity, displaying augmented activity toward the more toxic isomer P(-) of nerve agents, we synthesized new asymmetric fluorogenic OPs (Flu-OPs). Six Flu-OPs were prepared containing either ethyl (E), cyclohexyl (C) or pinacolyl (P) alkyl radicals attached to methyl-phosphonyl (MP) moiety analogous to the structure of VX, GF and soman, respectively. The fluorescent moieties are either 3-cyano-4-methyl-7-hydroxy coumarin (MeCyC) or 1,3-dichloro-7-hydroxy-9,9-dimethyl-9H-acridin-2-one (DDAO). The kinetics of AChE and BChE inhibition by these new Flu-OPs display k(i) values 8.5x10(4) to 8.5x10(7) and 5x10(4) to 2x10(6)M(-1)min(-1), respectively. EMP-MeCyC and EMP-DDAO are the most active inhibitors of AChE whereas CMP-MeCyC and CMP-DDAO are better inhibitors of BChE than AChE, indicating accommodation of bulky cyclohexyl group inside the active site of BChE. PMP-MeCyC and PMP-DDAO are the least active inhibitors of both AChE and BChE. CMP-MeCyC and CMP-DDAO were significantly detoxified only by the five-site mutations PON1 variant L69V/S138L/S193P/N287D/V346A. Degradation kinetics of Flu-OPs measured by increase in absorbance of the released fluorogenic group was fit by a two exponential function, indicating faster hydrolysis of the less toxic optical isomer. Interestingly, wt PON1 caused only 50% degradation of racemic EMP-MeCyC, CMP-MeCyC and CMP-DDAO indicating complete hydrolysis of P(+) isomer. This remarkable stereoselectivity was used for the enzymatic separation of the P(-) isomer of CMP-MeCyC. The bimolecular rate constant k(i) for human AChE inhibition by the isolated P(-) isomer of CMP-MeCyC is five-fold larger than that of its P(+) isomer. The marked preference of wt PON1 toward P(+) stereo-isomer of CMP-MeCyC and CMP-DDAO renders their P(-) stereo-isomers suitable for the selection of new OP hydrolase variants with reversed stereoselectivity.
Collapse
Affiliation(s)
- Gabi Amitai
- Division of Medicinal Chemistry, Israel Institute for Biological Research, PO Box 19, Ness Ziona 74100, Israel.
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Huang LF, Su B, Jao SC, Liu KT, Li WS. Aminopeptidase p mediated detoxification of organophosphonate analogues of sarin: mechanistic and stereochemical study at the phosphorus atom of the substrate. Chembiochem 2006; 7:506-14. [PMID: 16470765 DOI: 10.1002/cbic.200500412] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The activity of the aminopeptidase P from Escherichia coli in hydrolyzing a series of organophosphonate sarin analogues (1-6) was evaluated. The enzymatic rates of hydrolysis for methylphosphonate 1 with a methoxy group attached to the phosphorus center were 7- to 15-fold higher than those for the corresponding analogues 2-6. Double mutant R153W/R370L was able to hydrolyze the S(p) enantiomer of racemic 1 at a considerable rate. This mutant allowed the preparation of the R(p) isomer of the sarin analogue 1. All the mutants, R370L, R153A, W88L, R153L/R370L, and R153W/R370L, preferred the formation of (S(p))-8 to that of the corresponding (R(p))-8 enantiomer and displayed a better enantiomeric excess of products, by 1.4- to 2-fold as compared to the wild-type enzyme. Enzymatic hydrolysis of O,O-diisopropyl-p-nitrophenyl phosphate (9) in H(2) (18)O led to the formation of the (18)O-labeled O,O-diisopropyl phosphate product and confirmed that the catalytic reaction starts with cleavage of the P--O bond. From chemical and kinetic studies, the utilization of an optically pure S(p) enantiomer of O-methyl-p-nitrophenyl methylphosphonothioate (S(p))-MNMPT, 7) has demonstrated that the enzymatic reaction proceeds through a displacement mechanism and generates a chiral product in situ with an inversion of stereochemical configuration at the phosphorus atom. The results also lead to the conclusion that alteration of the active site through site-directed mutagenesis can result in a preference for (S(p))-MNMPT (7) rather than the R(p) isomer.
Collapse
Affiliation(s)
- Li-Fang Huang
- Institute of Chemistry, Academia Sinica, 128 Academia Road Sec. 2, Taipei 115, Taiwan
| | | | | | | | | |
Collapse
|
33
|
Amitai G, Gaidukov L, Adani R, Yishay S, Yacov G, Kushnir M, Teitlboim S, Lindenbaum M, Bel P, Khersonsky O, Tawfik DS, Meshulam H. Enhanced stereoselective hydrolysis of toxic organophosphates by directly evolved variants of mammalian serum paraoxonase. FEBS J 2006; 273:1906-19. [PMID: 16640555 DOI: 10.1111/j.1742-4658.2006.05198.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We addressed the ability of various organophosphorus (OP) hydrolases to catalytically scavenge toxic OP nerve agents. Mammalian paraoxonase (PON1) was found to be more active than Pseudomonas diminuta OP hydrolase (OPH) and squid O,O-di-isopropyl fluorophosphatase (DFPase) in detoxifying cyclosarin (O-cyclohexyl methylphosphonofluoridate) and soman (O-pinacolyl methylphosphonofluoridate). Subsequently, nine directly evolved PON1 variants, selected for increased hydrolytic rates with a fluorogenic diethylphosphate ester, were tested for detoxification of cyclosarin, soman, O-isopropyl-O-(p-nitrophenyl) methyl phosphonate (IMP-pNP), DFP, and chlorpyrifos-oxon (ChPo). Detoxification rates were determined by temporal acetylcholinesterase inhibition by residual nonhydrolyzed OP. As stereoisomers of cyclosarin and soman differ significantly in their acetylcholinesterase-inhibiting potency, we actually measured the hydrolysis of the more toxic stereoisomers. Cyclosarin detoxification was approximately 10-fold faster with PON1 mutants V346A and L69V. V346A also exhibited fourfold and sevenfold faster hydrolysis of DFP and ChPo, respectively, compared with wild-type, and ninefold higher activity towards soman. L69V exhibited 100-fold faster hydrolysis of DFP than the wild-type. The active-site mutant H115W exhibited 270-380-fold enhancement toward hydrolysis of the P-S bond in parathiol, a phosphorothiolate analog of parathion. This study identifies three key positions in PON1 that affect OP hydrolysis, Leu69, Val346 and His115, and several amino-acid replacements that significantly enhance the hydrolysis of toxic OPs. GC/pulsed flame photometer detector analysis, compared with assay of residual acetylcholinesterase inhibition, displayed stereoselective hydrolysis of cyclosarin, soman, and IMP-pNP, indicating that PON1 is less active toward the more toxic optical isomers.
Collapse
Affiliation(s)
- Gabriel Amitai
- Division of Medicinal Chemistry, Israel Institute for Biological Research, Ness Ziona, Israel.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Park MS, Hill CM, Li Y, Hardy RK, Khanna H, Khang YH, Raushel FM. Catalytic properties of the PepQ prolidase from Escherichia coli. Arch Biochem Biophys 2004; 429:224-30. [PMID: 15313226 DOI: 10.1016/j.abb.2004.06.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Revised: 06/22/2004] [Indexed: 10/26/2022]
Abstract
The PepQ prolidase from Escherichia coli catalyzes the hydrolysis of dipeptide substrates with a proline residue at the C-terminus. The pepQ gene has been cloned, overexpressed, and the enzyme purified to homogeneity. The k(cat) and k(cat)/K(m) values for the hydrolysis of Met-Pro are 109 s(-1) and 8.4 x 10(5)M(-1)s(-1), respectively. The enzyme also catalyzes the stereoselective hydrolysis of organophosphate triesters and organophosphonate diesters. A series of 16 organophosphate triesters with a p-nitrophenyl leaving group were assessed as substrates for PepQ. The S(P)-enantiomer of methyl phenyl p-nitrophenyl phosphate was hydrolyzed with a k(cat) of 36 min(-1) and a k(cat)/K(m) of 710 M(-1)s(-1). The corresponding R(P)-enantiomer was hydrolyzed more slowly with a k(cat) of 0.4 min(-1) and a k(cat)/K(m) of 11 M(-1)s(-1). The PepQ prolidase can be utilized for the kinetic resolution of racemic phosphate esters. The PepQ prolidase was shown to hydrolyze the p-nitrophenyl analogs of the nerve agents GB (sarin), GD (soman), GF, and VX.
Collapse
Affiliation(s)
- Min-Sun Park
- Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, TX 77842-3012, USA
| | | | | | | | | | | | | |
Collapse
|
35
|
Sogorb MA, Vilanova E, Carrera V. Future applications of phosphotriesterases in the prophylaxis and treatment of organophosporus insecticide and nerve agent poisonings. Toxicol Lett 2004; 151:219-33. [PMID: 15177657 DOI: 10.1016/j.toxlet.2004.01.022] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Revised: 01/28/2004] [Accepted: 01/29/2004] [Indexed: 12/23/2022]
Abstract
Organophosphorus compounds (OPs) are being used as insecticides and warfare agents. OP insecticides represent an important problem of public health, causing around 200,000 deaths annually. The World Health Organization has pointed to the necessity to introduce new medical practices that improve the results of classical treatments. Many studies have shown that the administration of phosphotriesterases (enzymes that detoxify OPs through hydrolysis) is a promising treatment of persons poisoned with OPs. Such an enzyme-based treatment might introduce important improvements in the treatment of patients having ingested large amounts of OPs. Phosphotriesterases might also be suitable for prophylactic treatment of persons at risk to be severely exposed. The new experimental treatments do not exhibit the intrinsic neurotoxicity of the classical prophylaxis based on carbamates and antimuscarinic drugs. Experimental data suggest that might be time to initiate clinical trials in order to study the efficacy of phosphotriesterases in the therapy and prophylaxis of OP intoxication.
Collapse
Affiliation(s)
- Miguel A Sogorb
- División de Toxicología, Instituto de Bioingeniería, Universidad Miguel Hernández, Avenida de la Universidad s/n, 03202 Elche, Spain.
| | | | | |
Collapse
|
36
|
Abstract
Bacterial enzymes have been isolated that catalyze the hydrolysis of organophosphate nerve agents with high-rate enhancements and broad substrate specificity. Mutant forms of these enzymes have been constructed through rational redesign of the active-site binding pockets and random mutagenesis to create protein variants that are optimized for the detoxification of agricultural insecticides and chemical warfare agents. In this review, the catalytic properties of two bacterial enzymes, phosphotriesterase and organophosphorus anhdrolase, are examined for their ability to hydrolyze organophosphate nerve agents.
Collapse
Affiliation(s)
- Frank M Raushel
- Department of Chemistry, PO Box 30012, Texas A&M University, College Station, Texas 77842-3012, USA.
| |
Collapse
|
37
|
Moss RA, Gong PK, Morales-Rojas H. Stereochemical study of phosphonothioate cleavage by a metallomicelle. Org Lett 2002; 4:1835-8. [PMID: 12027626 DOI: 10.1021/ol0200394] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] The copper metallomicellar hydrolysis of O-methyl O-4-nitrophenyl phenylphosphonothioate to O-methyl phenylphosphonothioic acid takes place with effectively complete inversion at phosphorus.
Collapse
Affiliation(s)
- Robert A Moss
- Department of Chemistry, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA.
| | | | | |
Collapse
|
38
|
Sogorb MA, Vilanova E. Enzymes involved in the detoxification of organophosphorus, carbamate and pyrethroid insecticides through hydrolysis. Toxicol Lett 2002; 128:215-28. [PMID: 11869832 DOI: 10.1016/s0378-4274(01)00543-4] [Citation(s) in RCA: 331] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The most employed insecticides for indoor and agriculture purposes belong to carbamates, pyrethroid or organophosphates. The chemical structures of these three groups correspond to carbamic, carboxylic and triphosphoric esters. Technical monographs suggest that the hydrolysis of ester bonds of carbamates and pyrethroids plays an important role in the detoxification of these compounds. However, detailed studies about enzymes hydrolysing carbamates and pyrethroids in vertebrates are not available. Certain carbamate hydrolysing activities are associated to serum albumin. Phosphotriesterases, being of an unknown physiological role, hydrolyse (in some cases stereospecifically) organophosphorus insecticides (OP). Phosphotriesterases have been found in a multitude of species, from mammals to bacteria. A phosphotriesterase activity, EDTA-resistant, has been detected in serum albumin. Phosphotriesterases in serum of mammals display polymorphisms. Phosphotriesterases offer applications in therapy of organophosphorus poisonings, in biodegradation and bioremedation of organophosphates. Similar studies should be developed with enzymes hydrolysing pyrethroids and carbamate insecticides. Such studies will improve the knowledge of the detoxification routes in non-target species and will help to design specific and safer carbamate and pyrethroid insecticides.
Collapse
Affiliation(s)
- Miguel A Sogorb
- División de Toxicología, Instituto de Bioingeniería, Universidad Miguel Hernández, Av. del Ferrocarril s/n. 03202, Elche, Spain.
| | | |
Collapse
|