A Reactivator of Organophosphorus Nerve Agent-Inhibited Human Acetylcholinesterase: Characterization, Mechanistic Insights and Design
Date
2016
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Publisher
University of Delaware
Abstract
Organophosphorus nerve agents are highly toxic compounds which pose a threat worldwide. These compounds induce toxicity by covalently binding to the active site serine of acetylcholinesterase, which results in inhibition of the enzyme. Without functional acetylcholinesterase, the levels of the neurotransmitter acetylcholine in neuromuscular junctions rise quickly causing overstimulation of the nervous system, which will culminate in death if not treated. Current treatments rely on small molecules to interact with inhibited enzyme to disrupt the covalently bound phosphorus moiety at the active site. The most effective molecules incorporate a pyridinium oxime which acts via direct nucleophilic attack on the phosphorus to achieve reactivation of the enzyme. These compounds have limited effectiveness as the charged portion of the molecule does not allow them to cross into the central nervous system where acetylcholinesterase inhibition is most harmful. This study characterizes a small molecule reactivator that does not incorporate an oxime but is capable of reactivating nerve agent-inhibited enzyme as well as or better than current treatments in vitro. Through the use of a structure-activity relationship study and several biochemical techniques, the phenol moiety of 4-amino-2-((diethylamino)methyl)phenol (ADOC) was determined to be essential for the reactivation characteristics of this molecule, likely through an indirect water-activation mechanism. This information was then used in the design of a second-generation molecule that showed increased reactivation potential.
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Keywords
Acetylcholinesterase, Mechanism, Nerve agent, Organophosphorus, Oxime, Reactivator