title: In search of a catalytic bioscavenger for the prophylaxis of nerve agent toxicity.
abstract: A novel approach for treating organophosphorus (OP) poisoning is the use of enzymes, both stoichiometric and catalytic, as bioscavengers to sequester these compounds in circulation before they reach their physiological targets. Human serum butyrylcholinesterase and a recombinant form of this enzyme produced in the milk of transgenic goats have completed Phase I clinical trials as stoichiometric bioscavengers for the protection of humans against OP nerve agents. However, a major limitation of the first generation bioscavenger is the 1:1 stoichiometry between the enzyme and the OP. Therefore, efforts are underway to develop the second generation catalytic bioscavenger, which will neutralize/hydrolyze multiple OP molecules. To avoid any complications related to adverse immune reactions, three enzymes from human (Hu) sources are being considered for development as catalytic bioscavengers: (1) prolidase; (2) paraoxonase 1 (PON1); (3) senescence marker protein-30 (SMP-30). Towards this effort, native or recombinant (r) forms of candidate catalytic bioscavengers were isolated and characterized for their ability to hydrolyze G-type nerve agents at concentrations of 10muM and 1mM. Results show that mammalian enzymes were significantly less efficient at hydrolyzing nerve agents as compared to bacterial organophosphorus hydrolase (OPH) and organophosphorus acid anhydrolase (OPAA). Recombinant Hu prolidase was the most efficient and the only mammalian enzyme that hydrolyzed all four G-type nerve agents. On the other hand, both rHu PON1 and Mo SMP-30 showed 10-fold lower activity towards sarin compared to rHu prolidase and did not hydrolyze tabun. Based on these results, Hu prolidase appears to be the most promising candidate for further development: (1) it can be easily expressed in E. coli; (2) of the three candidate enzymes, it is the only enzyme that hydrolyzes all four G-type agents. Efforts to improve the catalytic efficiency of this enzyme towards OP nerve agents are underway.
authors.affiliation: Division of Bacterial and Rickettsial Diseases, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD 20910-7500, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: diTargiani
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Chandrasekaran
authors.forename: Tatyana
authors.initials: T
authors.lastname: Belinskaya
authors.forename: Ashima
authors.initials: A
authors.lastname: Saxena
mesh_terms: D000818:Animals; D000931:Antidotes / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D043303:Aryldialkylphosphatase / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D055162:Biocatalysis; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020134:Catalytic Domain; D002619:Chemical Warfare Agents / Q000378:metabolism* / Q000633:toxicity*; D004150:Dipeptidases / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D055808:Drug Discovery; D006801:Humans; D006868:Hydrolysis; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D009943:Organophosphorus Compounds / Q000378:metabolism / Q000633:toxicity; D044345:Phosphoric Triester Hydrolases / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000931:Antidotes; D002135:Calcium-Binding Proteins; D002619:Chemical Warfare Agents; D047908:Intracellular Signaling Peptides and Proteins; D009943:Organophosphorus Compounds; C513324:Rgn protein, mouse; D044345:Phosphoric Triester Hydrolases; D043303:Aryldialkylphosphatase; C020061:diisopropyl-fluorophosphatase; D004150:Dipeptidases; C022449:proline dipeptidase