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Lockridge O, Schopfer LM. Review: Organophosphorus toxicants, in addition to inhibiting acetylcholinesterase activity, make covalent adducts on multiple proteins and promote protein crosslinking into high molecular weight aggregates. Chem Biol Interact 2023; 376:110460. [PMID: 36963650 PMCID: PMC10100150 DOI: 10.1016/j.cbi.2023.110460] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 03/08/2023] [Accepted: 03/15/2023] [Indexed: 03/26/2023]
Abstract
The acute effects of exposure to organophosphorus toxicants are explained by inhibition of acetylcholinesterase activity. However, the mechanisms that explain long term illness associated with organophosphorus exposure are still under investigation. We find that organophosphorus nerve agents and organophosphorus pesticides make covalent adducts not only on the serine from acetylcholinesterase, but also on tyrosine, lysine, glutamate, serine and threonine from a variety of proteins. Almost any protein can be modified by a high dose of organophosphorus toxicant. A low dose of 10 μM chlorpyrifos oxon added to the serum-free culture medium of human neuroblastoma SH-SY5Y cells resulted in tyrosine adducts on 48 proteins immunopurified from the cell lysate. We identified the adducted proteins by mass spectrometry after immunopurifying modified proteins with a rabbit anti-diethoxyphospho-tyrosine monoclonal antibody which biased this study for tyrosine adducts. In cultured cells, the primary organophosphate targets are abundant proteins. Organophosphate-modified proteins may disrupt physiological processes. In separate experiments we identified organophosphate adducts on lysine. Organophosphylation activates the lysine for protein crosslinking. The activated lysine reacts with glutamic acid or aspartic acid protein side chains to form an isopeptide bond between proteins, resulting in high molecular weight crosslinked proteins. Crosslinked proteins form insoluble aggregates that may lead to neurogenerative disease.
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Affiliation(s)
- Oksana Lockridge
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
| | - Lawrence M Schopfer
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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2
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Schnettler JD, Klein OJ, Kaminski TS, Colin PY, Hollfelder F. Ultrahigh-Throughput Directed Evolution of a Metal-Free α/β-Hydrolase with a Cys-His-Asp Triad into an Efficient Phosphotriesterase. J Am Chem Soc 2023; 145:1083-1096. [PMID: 36583539 PMCID: PMC9853848 DOI: 10.1021/jacs.2c10673] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Finding new mechanistic solutions for biocatalytic challenges is key in the evolutionary adaptation of enzymes, as well as in devising new catalysts. The recent release of man-made substances into the environment provides a dynamic testing ground for observing biocatalytic innovation at play. Phosphate triesters, used as pesticides, have only recently been introduced into the environment, where they have no natural counterpart. Enzymes have rapidly evolved to hydrolyze phosphate triesters in response to this challenge, converging onto the same mechanistic solution, which requires bivalent cations as a cofactor for catalysis. In contrast, the previously identified metagenomic promiscuous hydrolase P91, a homologue of acetylcholinesterase, achieves slow phosphotriester hydrolysis mediated by a metal-independent Cys-His-Asp triad. Here, we probe the evolvability of this new catalytic motif by subjecting P91 to directed evolution. By combining a focused library approach with the ultrahigh throughput of droplet microfluidics, we increase P91's activity by a factor of ≈360 (to a kcat/KM of ≈7 × 105 M-1 s-1) in only two rounds of evolution, rivaling the catalytic efficiencies of naturally evolved, metal-dependent phosphotriesterases. Unlike its homologue acetylcholinesterase, P91 does not suffer suicide inhibition; instead, fast dephosphorylation rates make the formation of the covalent adduct rather than its hydrolysis rate-limiting. This step is improved by directed evolution, with intermediate formation accelerated by 2 orders of magnitude. Combining focused, combinatorial libraries with the ultrahigh throughput of droplet microfluidics can be leveraged to identify and enhance mechanistic strategies that have not reached high efficiency in nature, resulting in alternative reagents with novel catalytic machineries.
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Affiliation(s)
- J David Schnettler
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Oskar James Klein
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Tomasz S Kaminski
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Pierre-Yves Colin
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Florian Hollfelder
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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3
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Vokuev MF, Baygildiev ТМ, Plyushchenko IV, Ikhalaynen YA, Ogorodnikov RL, Solontsov IK, Braun АV, Savelieva EI, Rуbalchenko IV, Rodin IA. Untargeted and targeted analysis of sarin poisoning biomarkers in rat urine by liquid chromatography and tandem mass spectrometry. Anal Bioanal Chem 2021; 413:6973-6985. [PMID: 34549323 DOI: 10.1007/s00216-021-03655-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/01/2021] [Accepted: 09/08/2021] [Indexed: 12/14/2022]
Abstract
Chemical warfare agents continue to pose a real threat to humanity, despite their prohibition under the Chemical Weapons Convention. Sarin is one of the most toxic and lethal representatives of nerve agents. The methodology for the targeted analysis of known sarin metabolites has reached great heights, but little attention has been paid to the untargeted analysis of biological samples of victims exposed to this deadly poisonous substance. At present, the development of computational and statistical methods of analysis offers great opportunities for finding new metabolites or understanding the mechanisms of action or effect of toxic substances on the organism. This study presents the targeted LC-MS/MS determination of methylphosphonic acid and isopropyl methylphosphonic acid in the urine of rats exposed to a non-lethal dose of sarin, as well as the untarget urine analysis by LC-HRMS. Targeted analysis of polar acidic sarin metabolites was performed on a mixed-mode reversed-phase anion-exchange column, and untargeted analysis on a conventional reversed-phase C18 column. Isopropyl methylphosphonic acid was detected and quantified within 5 days after subcutaneous injection of sarin at a dose of 1/4 LD50. A combination of generalized additive mixed models and dose-response analysis with database searches using accurate mass of precursor ions and corresponding MS/MS spectra enabled us to propose new six potential biomarkers of biological response to exposure. The results confirm the well-known fact that sarin poisoning has a significant impact on the victims' metabolome, with inhibition of acetylcholinesterase being just the first step and trigger of the complex toxicodynamic response.
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Affiliation(s)
- M F Vokuev
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia.
| | - Т М Baygildiev
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - I V Plyushchenko
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Y A Ikhalaynen
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - R L Ogorodnikov
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - I K Solontsov
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - А V Braun
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia.,Laboratory for the Chemical and Analytical Control of the Military Research Centre, 105005, Moscow, Russia
| | - E I Savelieva
- Research Institute of Hygiene, Occupational Pathology and Human Ecology Federal State Unitary Enterprise, Federal Medical Biological Agency of Russia, Kuz'molovsky g/p, 188663, Leningrad Region, Russia
| | - I V Rуbalchenko
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia.,Laboratory for the Chemical and Analytical Control of the Military Research Centre, 105005, Moscow, Russia
| | - I A Rodin
- Department of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia.,Department of Epidemiology and Evidence Based Medicine, I.M. Sechenov First Moscow State Medical University, Moscow, Russia
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4
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Extended retrospective detection of regenerated sarin (GB) in rabbit blood and the IMPA metabolite in urine: a pharmacokinetics study. Arch Toxicol 2021; 95:2403-2412. [PMID: 34032868 DOI: 10.1007/s00204-021-03085-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/17/2021] [Indexed: 10/21/2022]
Abstract
Long-term retrospective monitoring of exposure to organophosphorus nerve agents is challenging. We recently developed two highly sensitive analytical methods for regenerated sarin (GB) nerve agent in blood and its primary metabolite, isopropyl-methylphosphonic acid (IMPA), in urine. These methods were implemented in a toxicokinetics study carried out with sarin injected (i.v.) to rabbits at doses corresponding to 0.1, 0.5 or 0.9 LD50. The time frame for monitoring regenerated sarin from blood was 70 days for 0.1 LD50 and 0.5 LD50 and 77 days for 0.9 LD50, where rapid elimination occurred in the first 8 days with an initial average half-life of 1.2 days, followed by a second, slower elimination, with a terminal average half-life of 8.4 days. The time frame for monitoring IMPA in urine was 7, 15 and 16 days for 0.1 LD50, 0.5 LD50 and 0.9 LD50 intoxications, respectively. Rapid elimination of IMPA in urine occurred after exposure, with an average half-life of ~ 0.8 days on days 2-6. For the first time, a slower elimination route for IMPA, with an average half-life of ~ 4 days from day 6 onwards, was revealed. Both IMPA and regenerated sarin pharmacokinetics exhibit linearity with dose. The overlaid pharmacokinetic profiles of regenerated sarin in blood along with IMPA in urine emphasize the dominance of IMPA with a rapid decay in urine in the first week and the slower long-term decay of protein-bound sarin later in blood. To our knowledge, the two new sensitive methods exhibit the longest monitoring time frame reported in biological samples.
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Lu X, Zhang Z, Gao R, Wang H, Xiao J. Recent progress in the chemical attribution of chemical warfare agents and highly toxic organophosphorus pesticides. Forensic Toxicol 2021. [DOI: 10.1007/s11419-021-00578-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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6
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Glaros T, Dhummakupt ES, Rizzo GM, McBride E, Carmany DO, Wright LKM, Forster JS, Renner JA, Moretz RW, Dorsey R, Marten MR, Huso W, Doan A, Dorsey CD, Phillips C, Benton B, Mach PM. Discovery of treatment for nerve agents targeting a new metabolic pathway. Arch Toxicol 2020; 94:3249-3264. [PMID: 32720192 PMCID: PMC7415758 DOI: 10.1007/s00204-020-02820-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 06/18/2020] [Indexed: 11/19/2022]
Abstract
The inhibition of acetylcholinesterase is regarded as the primary toxic mechanism of action for chemical warfare agents. Recently, there have been numerous reports suggesting that metabolic processes could significantly contribute to toxicity. As such, we applied a multi-omics pipeline to generate a detailed cascade of molecular events temporally occurring in guinea pigs exposed to VX. Proteomic and metabolomic profiling resulted in the identification of several enzymes and metabolic precursors involved in glycolysis and the TCA cycle. All lines of experimental evidence indicated that there was a blockade of the TCA cycle at isocitrate dehydrogenase 2, which converts isocitrate to α-ketoglutarate. Using a primary beating cardiomyocyte cell model, we were able to determine that the supplementation of α-ketoglutarate subsequently rescued cells from the acute effects of VX poisoning. This study highlights the broad impacts that VX has and how understanding these mechanisms could result in new therapeutics such as α-ketoglutarate.
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Affiliation(s)
- Trevor Glaros
- Research and Technology Directorate, BioSciences Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Building E3150, Aberdeen Proving Ground, Gunpowder, MD, 21010, USA.
- BioSciences Division, B11 Bioenergy and Biome Sciences, Los Alamos National Laboratory, SM30, Mailstop E529, PO Box 1663, Los Alamos, NM, 87545, USA.
| | - Elizabeth S Dhummakupt
- Research and Technology Directorate, BioSciences Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Building E3150, Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Gabrielle M Rizzo
- Excet, Inc., 6225 Brandon Ave, Suite 360, Springfield, VA, 22150, USA
| | - Ethan McBride
- Research and Technology Directorate, BioSciences Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Building E3150, Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
- National Academies of Sciences, Engineering, and Medicine, NRC Research Associateship Programs, 500 Fifth Street, NW, Washington, DC, 20001, USA
| | - Daniel O Carmany
- Excet, Inc., 6225 Brandon Ave, Suite 360, Springfield, VA, 22150, USA
| | - Linnzi K M Wright
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Jeffry S Forster
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Julie A Renner
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Ruth W Moretz
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Russell Dorsey
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Mark R Marten
- Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore County (UMBC), Engineering Building, Baltimore, MD, USA
| | - Walker Huso
- Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore County (UMBC), Engineering Building, Baltimore, MD, USA
| | - Alexander Doan
- Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore County (UMBC), Engineering Building, Baltimore, MD, USA
| | - Carrie D Dorsey
- Kirk U.S. Army Health Clinic, 6455 Machine Rd., Aberdeen Proving Ground, Gunpowder, MD, 21005, USA
| | - Christopher Phillips
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Bernard Benton
- Research and Technology Directorate, Toxicology and Obscurants Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Aberdeen Proving Ground, Gunpowder, MD, 21010, USA
| | - Phillip M Mach
- Research and Technology Directorate, BioSciences Division, Combat Capabilities Development Command (CCDC) Chemical Biological Center, 5183 Blackhawk Rd., Building E3150, Aberdeen Proving Ground, Gunpowder, MD, 21010, USA.
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7
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Fu F, Liu H, Lu X, Zhang R, Li L, Gao R, Xie J, Wang H, Pei C. Identification of S419 on human serum albumin as a novel biomarker for sarin and cyclosarin exposure. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34:e8721. [PMID: 31899842 DOI: 10.1002/rcm.8721] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 12/19/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
RATIONALE Organophosphorus nerve agents are highly toxic because they inhibit acetylcholinesterase activity, thereby causing a series of symptomatic poisoning. Upon entering the body, nerve agents bind active amino acid residues to form phosphonylated adducts. A potentially beneficial method for specific verification of exposure of nerve agents is based on albumin adducts, which have a half-life of 18 days. This appears to be more effective than the fluoride reactivation method, based on acetylcholinesterase. METHODS After the exposure of human serum albumin to nine nerve agents, human serum albumin was denatured, reduced, alkylated and digested with trypsin according to standard mass spectrometry-based proteomics procedures. The phosphonylated peptides of human serum albumin were identified using positive ion electrospray ionization with a quadrupole orbitrap mass spectrometer. RESULTS The peptide KVPQVSTPTLVESR showed a good mass spectrometric response to the nine nerve agents. The tendency of sarin and cyclosarin was to bind to S419 on the peptide, while the other nerve agents (tabun, soman and V-type nerve agents) were shown to bind more readily to K414 on the peptide. CONCLUSIONS This research revealed a new site, S419, of the tryptic peptide KVPQVSTPTLVEVSR on human albumin to be a valuable biomarker for sarin/cyclosarin exposure, helping to further distinguish sarin and cyclosarin poisoning from that of other nerve agents and providing an important tool for the identification of sarin or cyclosarin in terrorist attacks.
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Affiliation(s)
- Feiyan Fu
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Haibo Liu
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Xiaogang Lu
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Ruihua Zhang
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Liqin Li
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Runli Gao
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Jianwei Xie
- Beijing Institute of Pharmacology and Toxicology, Beijing, 100850, China
| | - Hongmei Wang
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
| | - Chengxin Pei
- State Key Laboratory of NBC Protection for Civilians, Beijing, 102205, China
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8
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Bouknight KD, Jurkouich KM, Compton JR, Khavrutskii IV, Guelta MA, Harvey SP, Legler PM. Structural and kinetic evidence of aging after organophosphate inhibition of human Cathepsin A. Biochem Pharmacol 2020; 177:113980. [PMID: 32305437 DOI: 10.1016/j.bcp.2020.113980] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 04/14/2020] [Indexed: 11/30/2022]
Abstract
Human Cathepsin A (CatA) is a lysosomal serine carboxypeptidase of the renin-angiotensin system (RAS) and is structurally similar to acetylcholinesterase (AChE). CatA can remove the C-terminal amino acids of endothelin I, angiotensin I, Substance P, oxytocin, and bradykinin, and can deamidate neurokinin A. Proteomic studies identified CatA and its homologue, SCPEP1, as potential targets of organophosphates (OP). CatA could be stably inhibited by low µM to high nM concentrations of racemic sarin (GB), soman (GD), cyclosarin (GF), VX, and VR within minutes to hours at pH 7. Cyclosarin was the most potent with a kinetically measured dissociation constant (KI) of 2 µM followed by VR (KI = 2.8 µM). Bimolecular rate constants for inhibition by cyclosarin and VR were 1.3 × 103 M-1sec-1 and 1.2 × 103 M-1sec-1, respectively, and were approximately 3-orders of magnitude lower than those of human AChE indicating slower reactivity. Notably, both AChE and CatA bound diisopropylfluorophosphate (DFP) comparably and had KIDFP = 13 µM and 11 µM, respectively. At low pH, greater than 85% of the enzyme spontaneously reactivated after OP inhibition, conditions under which OP-adducts of cholinesterases irreversibly age. At pH 6.5 CatA remained stably inhibited by GB and GF and <10% of the enzyme spontaneously reactivated after 200 h. A crystal structure of DFP-inhibited CatA was determined and contained an aged adduct. Similar to AChE, CatA appears to have a "backdoor" for product release. CatA has not been shown previously to age. These results may have implications for: OP-associated inflammation; cardiovascular effects; and the dysregulation of RAS enzymes by OP.
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Affiliation(s)
- Kayla D Bouknight
- Hampton University, 100 E Queen St, Hampton, VA 23668, United States
| | - Kayla M Jurkouich
- Case Western Reserve University, Dept. of Biomedical Engineering, Cleveland, 10900 Euclid Avenue, OH 44106, United States
| | - Jaimee R Compton
- U.S. Naval Research Laboratory, 4555 Overlook Ave., Washington, DC 20375, United States
| | - Ilja V Khavrutskii
- Uniformed Services University, Armed Forces Radiobiology Research Institute, 4301 Jones Bridge Rd., Bethesda, MD 20889-5648, United States
| | - Mark A Guelta
- U.S. Army Combat Capabilities and Development Command Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, MD 21010, United States
| | - Steven P Harvey
- U.S. Army Combat Capabilities and Development Command Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, MD 21010, United States
| | - Patricia M Legler
- U.S. Naval Research Laboratory, 4555 Overlook Ave., Washington, DC 20375, United States.
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9
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Lin VS, Volk RF, DeLeon AJ, Anderson LN, Purvine SO, Shukla AK, Bernstein HC, Smith JN, Wright AT. Structure Dependent Determination of Organophosphate Targets in Mammalian Tissues Using Activity-Based Protein Profiling. Chem Res Toxicol 2019; 33:414-425. [DOI: 10.1021/acs.chemrestox.9b00344] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Vivian S. Lin
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Regan F. Volk
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Adrian J. DeLeon
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Lindsey N. Anderson
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Samuel O. Purvine
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Anil K. Shukla
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Hans C. Bernstein
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
- Faculty of Biosciences, Fisheries and Economics, UiT - The Arctic University of Norway, Tromsø 9019, Norway
- The Arctic Centre for Sustainable Energy, UiT - The Arctic University of Norway, Tromsø 9019, Norway
| | - Jordan N. Smith
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Aaron T. Wright
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States
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Khavrutskii IV, Compton JR, Jurkouich KM, Legler PM. Paired Carboxylic Acids in Enzymes and Their Role in Selective Substrate Binding, Catalysis, and Unusually Shifted p Ka Values. Biochemistry 2019; 58:5351-5365. [PMID: 31192586 DOI: 10.1021/acs.biochem.9b00429] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cathepsin A (CatA, EC 3.4.16.5, UniProtKB P10619 ) is a human lysosomal carboxypeptidase. Counterintuitively, crystal structures of CatA and its homologues show a cluster of Glu and Asp residues binding the C-terminal carboxylic acid of the product or inhibitor. Each of these enzymes functions in an acidic environment and contains a highly conserved pair of Glu residues with side chain carboxyl group oxygens that are approximately 2.3-2.6 Å apart. In small molecules, carboxyl groups separated by ∼3 Å can overcome the repulsive interaction by protonation of one of the two groups. The pKa of one group increases (pKa ∼ 11) and can be as much as ∼6 pH units higher than the paired group. Consequently, at low and neutral pH, one carboxylate can carry a net negative charge while the other can remain protonated and neutral. In CatA, E69 and E149 form a Glu pair that is important to catalysis as evidenced by the 56-fold decrease in kcat/Km in the E69Q/E149Q variant. Here, we have measured the pH dependencies of log(kcat), log(Km), and log(kcat/Km) for wild type CatA and its variants and have compared the measured pKa with calculated values. We propose a substrate-assisted mechanism in which the high pKa of E149 (>8.5) favors the binding of the carboxylate form of the substrate and promotes the abstraction of the proton from H429 of the catalytic triad effectively decreasing its pKa in a low-pH environment. We also identify a similar motif consisting of a pair of histidines in S-formylglutathione hydrolase.
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Affiliation(s)
- Ilja V Khavrutskii
- Armed Forces Radiobiology Research Institute , Uniformed Services University , Bethesda , Maryland 20889-5648 , United States
| | - Jaimee R Compton
- U.S. Naval Research Laboratory , 4555 Overlook Avenue , Washington, D.C. 20375 , United States
| | - Kayla M Jurkouich
- Department of Biomedical Engineering , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Patricia M Legler
- U.S. Naval Research Laboratory , 4555 Overlook Avenue , Washington, D.C. 20375 , United States
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Carmany DO, Mach PM, Rizzo GM, Dhummakupt ES, McBride EM, Sekowski JW, Benton B, Demond PS, Busch MW, Glaros T. On-substrate Enzymatic Reaction to Determine Acetylcholinesterase Activity in Whole Blood by Paper Spray Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:2436-2442. [PMID: 30280314 PMCID: PMC6276064 DOI: 10.1007/s13361-018-2072-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 08/27/2018] [Accepted: 09/06/2018] [Indexed: 06/08/2023]
Abstract
Currently, all assays measuring acetylcholinesterase (AChE) activity following a suspected nerve agent exposure leverage methodologies that fail to identify the agent. This limits the overall effectiveness and ability to administer proper countermeasures. As such, there is an urgent need to identify novel, rapid, and more comprehensive approaches to establish AChE activity, including identification of the toxicant. Paper spray mass spectrometry was used to monitor the activity of acetylcholinesterase, both in-solution and on modified hydrophobic paper surface. Hydrophobic paper surfaces were prepared using vaporized trichloro(3,3,3-trifluoropropyl)silane. In both approaches, mixtures of diluted human whole blood with and without VX were mixed with a non-endogenous AChE specific substrate, 1,1-dimethyl-4-acetylthiomethylpiperidinium (MATP+). Formation of the cleaved MATP+ product was monitored over time and compared to MATP+ to determine relative AChE activity. This on-substrate assay was effective at determining AChE activity and identifying the toxicant; however, determination of AChE activity in-solution proceeded at a slower rate. The on-substrate assay serves as a pioneering example of an enzymatic reaction occurring on the surface of a paper spray ionization ticket. This work broadens the range of applications relating to paper spray ionization-based clinical diagnostic assays. Graphical Abstract ᅟ.
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Affiliation(s)
- Daniel O Carmany
- Excet, Inc., 6225 Brandon Ave, Suite 360, Springfield, VA, 22150, USA
| | - Phillip M Mach
- Biosciences Division, BioDefense Branch, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 21010, USA
| | - Gabrielle M Rizzo
- Excet, Inc., 6225 Brandon Ave, Suite 360, Springfield, VA, 22150, USA
| | - Elizabeth S Dhummakupt
- Biosciences Division, BioDefense Branch, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 21010, USA
| | - Ethan M McBride
- Biosciences Division, BioDefense Branch, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 21010, USA
| | - Jennifer W Sekowski
- Biosciences Division, BioDefense Branch, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 21010, USA
| | - Bernard Benton
- Toxicology and Obscurants Division, Analytical Toxicology Branch, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 21010, USA
| | - Paul S Demond
- Excet, Inc., 6225 Brandon Ave, Suite 360, Springfield, VA, 22150, USA
| | - Michael W Busch
- Excet, Inc., 6225 Brandon Ave, Suite 360, Springfield, VA, 22150, USA
| | - Trevor Glaros
- Biosciences Division, BioDefense Branch, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 21010, USA.
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Holmgren KH, Valdez CA, Magnusson R, Vu AK, Lindberg S, Williams AM, Alcaraz A, Åstot C, Hok S, Norlin R. Part 1: Tracing Russian VX to its synthetic routes by multivariate statistics of chemical attribution signatures. Talanta 2018; 186:586-596. [PMID: 29784407 DOI: 10.1016/j.talanta.2018.02.104] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/07/2018] [Accepted: 02/26/2018] [Indexed: 11/25/2022]
Abstract
Chemical attribution signatures (CAS) associated with different synthetic routes used for the production of Russian VX (VR) were identified. The goal of the study was to retrospectively determine the production method employed for an unknown VR sample. Six different production methods were evaluated, carefully chosen to include established synthetic routes used in the past for large scale production of the agent, routes involving general phosphorus-sulfur chemistry pathways leading to the agent, and routes whose main characteristic is their innate simplicity in execution. Two laboratories worked in parallel and synthesized a total of 37 batches of VR via the six synthetic routes following predefined synthesis protocols. The chemical composition of impurities and byproducts in each route was analyzed by GC/MS-EI and 49 potential CAS were recognized as important markers in distinguishing these routes using Principal Component Analysis (PCA). The 49 potential CAS included expected species based on knowledge of reaction conditions and pathways but also several novel compounds that were fully identified and characterized by a combined analysis that included MS-CI, MS-EI and HR-MS. The CAS profiles of the calibration set were then analyzed using partial least squares discriminant analysis (PLS-DA) and a cross validated model was constructed. The model allowed the correct classification of an external test set without any misclassifications, demonstrating the utility of this methodology for attributing VR samples to a particular production method. This work is part one of a three-part series in this Forensic VSI issue of a Sweden-United States collaborative effort towards the understanding of the CAS of VR in diverse batches and matrices. This part focuses on the CAS in synthesized batches of crude VR and in the following two parts of the series the influence of food matrices on the CAS profiles are investigated.
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Affiliation(s)
- Karin Höjer Holmgren
- The Swedish Defence Research Agency, FOI CBRN Defence and Security, SE-901 82 Umeå, Sweden
| | - Carlos A Valdez
- Forensic Science Center, Lawrence Livermore National Laboratory, 7000 East Avenue L-091, Livermore, California 94550, United States
| | - Roger Magnusson
- The Swedish Defence Research Agency, FOI CBRN Defence and Security, SE-901 82 Umeå, Sweden
| | - Alexander K Vu
- Forensic Science Center, Lawrence Livermore National Laboratory, 7000 East Avenue L-091, Livermore, California 94550, United States
| | - Sandra Lindberg
- The Swedish Defence Research Agency, FOI CBRN Defence and Security, SE-901 82 Umeå, Sweden
| | - Audrey M Williams
- Forensic Science Center, Lawrence Livermore National Laboratory, 7000 East Avenue L-091, Livermore, California 94550, United States
| | - Armando Alcaraz
- Forensic Science Center, Lawrence Livermore National Laboratory, 7000 East Avenue L-091, Livermore, California 94550, United States
| | - Crister Åstot
- The Swedish Defence Research Agency, FOI CBRN Defence and Security, SE-901 82 Umeå, Sweden
| | - Saphon Hok
- Forensic Science Center, Lawrence Livermore National Laboratory, 7000 East Avenue L-091, Livermore, California 94550, United States.
| | - Rikard Norlin
- The Swedish Defence Research Agency, FOI CBRN Defence and Security, SE-901 82 Umeå, Sweden.
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