title: Use of V agents and V-analogue compounds to probe the active site of atypical butyrylcholinesterase from Oryzias latipes.
abstract: The atypical butyrylcholinesterase (aBuChE) from Oryzias latipes shares approximately 65% sequence similarity to both acetylcholinesterase and butyrylcholinesterase and was studied for its capacity to spontaneously reactivate following inhibition by organophosphorus nerve agents. Like other cholinesterases, aBuChE was inhibited by all G- and V-type nerve agents. Interestingly, aBuChE was able to undergo spontaneous reactivation after inhibition with VR (t1/2= 5.5 ± 0.2 h). Mass spectrometry of aBuChE after VR inhibition confirmed the presence of a covalently bound adduct of the size expected for non-aged VR on the peptide containing the active site serine. To understand the effect of substrate volume on rates of reactivation, the capacity of aBuChE to bind and spontaneously reactivate after inhibition with five V-agent analogues was examined. No appreciable reactivation was detected for enzyme inhibited by V2 (VX with O-isopropyl on retained group), V4 (VX with N-diethyl leaving group termination), or V5 (VX with N-dimethyl leaving group termination). Minimal reactivation was detected with V1 (VX with O-propyl on retained group). Conversely, spontaneous reactivation was observed when aBuChE was inhibited by V3 (VX with O-isobutyl on retained group; t1/2= 6.3 ± 0.4 h). The data suggest that the ability of aBuChE to spontaneously reactivate after inhibition by V-agent analogues is related to the structure of the retained group. These results provide structural information that may shed light on the design of improved small molecule reactivators of nerve agent-inhibited acetylcholinesterase or butyrylcholinesterase, and further suggest that re-engineering the active site of a cholinesterase could result in enzymes with clinically relevant rates of nerve agent hydrolysis.
authors.affiliation: Physiology and Immunology Branch, Research Division, U.S. Army Medical Research Institute of Chemical Defense, 2900 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, United States.
authors.forename: Melanie G
authors.initials: MG
authors.lastname: Kirkpatrick
authors.affiliation: Medical Diagnostic and Chemical Branch, Analytical Toxicology Division, U.S. Army Medical Research Institute of Chemical Defense, 2900 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, United States.
authors.forename: Robert C
authors.initials: RC
authors.lastname: diTargiani
authors.affiliation: Pharmacology Branch, Research Division, U.S. Army Medical Research Institute of Chemical Defense, 2900 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, United States.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Sweeney
authors.affiliation: Physiology and Immunology Branch, Research Division, U.S. Army Medical Research Institute of Chemical Defense, 2900 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, United States. Electronic address: tamara.c.otto.civ@mail.mil.
authors.forename: Tamara C
authors.initials: TC
authors.lastname: Otto
mesh_terms: D000818:Animals; D002091:Butyrylcholinesterase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D006207:Half-Life; D007700:Kinetics; D007814:Larva / Q000378:metabolism; D013058:Mass Spectrometry; D009036:Moths / Q000254:growth & development / Q000378:metabolism; D009946:Organothiophosphorus Compounds / Q000737:chemistry* / Q000378:metabolism; D009990:Oryzias / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D002091:Butyrylcholinesterase; D009946:Organothiophosphorus Compounds; D011994:Recombinant Proteins; C009680:VX-agent
keywords: Cholinesterase; Nerve agent; Organophosphorus; Spontaneous reactivation