title: Novel nucleophiles enhance the human serum paraoxonase 1 (PON1)-mediated detoxication of organophosphates.
abstract: Paraoxonase 1 (PON1) is a calcium-dependent hydrolase associated with serum high-density lipoprotein particles. PON1 hydrolyzes some organophosphates (OPs), including some nerve agents, through nucleophilic attack of hydroxide ion (from water) in the active site. Most OPs are hydrolyzed inefficiently. This project seeks to identify nucleophiles that can enhance PON1-mediated OP degradation. A series of novel nucleophiles, substituted phenoxyalkyl pyridinium oximes, has been synthesized which enhance the degradation of surrogates of sarin (nitrophenyl isopropyl methylphosphonate; NIMP) and VX (nitrophenyl ethyl methylphosphonate; NEMP). Two types of in vitro assays have been conducted, a direct assay using millimolar concentrations of substrate with direct spectrophotometric quantitation of a hydrolysis product (4-nitrophenol) and an indirect assay using submicromolar concentrations of substrate with quantitation by the level of inhibition of an exogenous source of acetylcholinesterase from non-hydrolyzed substrate. Neither NIMP nor NEMP is hydrolyzed effectively by PON1 if one of these novel oximes is absent. However, in the presence of eight novel oximes, PON1-mediated degradation of both surrogates occurs. Computational modeling has created a model of PON1 embedded in phospholipid and has indicated general agreement of the binding enthalpies with the relative efficacy as PON1 enhancers. PON1 enhancement of degradation of OPs could be a unique and unprecedented mechanism of antidotal action.
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762 chambers@cvm.msstate.edu.
authors.forename: Janice E
authors.initials: JE
authors.lastname: Chambers
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762.
authors.forename: Howard W
authors.initials: HW
authors.lastname: Chambers
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Meek
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762.
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Funck
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762.
authors.forename: Manikanthan H
authors.initials: MH
authors.lastname: Bhavaraju
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Gwaltney
authors.affiliation: *Basic Sciences Department and Center for Environmental Health Sciences, College of Veterinary Medicine and Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Entomology Unit, and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762; Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807 and Department of Chemistry and Center for Environmental Health Sciences, Mississippi State University, Mississippi State, Mississippi 39762.
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Pringle
mesh_terms: D000931:Antidotes / Q000494:pharmacology*; D043303:Aryldialkylphosphatase / Q000097:blood*; D020134:Catalytic Domain; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology*; D006801:Humans; D006868:Hydrolysis; D006878:Hydroxides / Q000378:metabolism; D008658:Inactivation, Metabolic; D056004:Molecular Dynamics Simulation; D009596:Nitrophenols / Q000378:metabolism; D009946:Organothiophosphorus Compounds / Q000378:metabolism*; D010091:Oximes / Q000494:pharmacology*; D011726:Pyridinium Compounds / Q000494:pharmacology*; D012524:Sarin / Q000031:analogs & derivatives / Q000378:metabolism*; D013053:Spectrophotometry; D014867:Water / Q000378:metabolism
chemical_list: D000931:Antidotes; D043303:Aryldialkylphosphatase; D020536:Enzyme Activators; D006878:Hydroxides; D009596:Nitrophenols; D009946:Organothiophosphorus Compounds; D010091:Oximes; D011726:Pyridinium Compounds; D012524:Sarin; D014867:Water; C031356:hydroxide ion; C009680:VX-agent; C468406:PON1 protein, human; C024836:4-nitrophenol
keywords: PON1; VX surrogate; paraoxon; paraoxonase 1; sarin surrogate