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Two aging pathways for organophosphorus‐inhibited human butyrylcholinesterase resolved by MALDI‐TOF mass spectrometry
Author(s) -
Li He,
Nachon Florian,
Schopfer Lawrence M,
Masson Patrick,
Lockridge Okasana
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a896-b
Subject(s) - chemistry , butyrylcholinesterase , nerve agent , tabun , acetylcholinesterase , bond cleavage , stereochemistry , paraoxon , mass spectrometry , serine , organophosphate , electrospray ionization , sarin , enzyme , biochemistry , chromatography , aché , pesticide , agronomy , biology , catalysis
Organophosphorus (OP) compounds inhibit serine hydrolases such as cholinesterases by phosphylation of the active site serine, forming a stable conjugate. The inhibited enzyme can be reactivated by nucleophilic agents. However, the covalently bound OP can also undergo a time‐dependent aging process leading to a nonreactivatable enzyme. This process involves hydrolysis of a phosphorus‐alkyl ligand bond (P‐X‐C, where X can be oxygen, sulfur, or nitrogen). The aging mechanisms for acetylcholinesterase (AChE) inhibited by soman or tabun; and butyrylcholinesterase (BChE) inhibited by isomalathion have been previously investigated. Soman inhibited AChE ages by hydrolyzing the O‐C portion of the phospho‐bond; tabun, the P‐N portion; and isomalathion, the P‐S portion. Our work utilized matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry to systematically study the aging mechanism of human BChE inhibited by OP compounds. Inhibited BChE was aged in the presence of H 2 O 18 and subsequently trypsinized. We identified the peptide OP conjugates through peptide mass mapping. Our results show that BChE inhibited by dichlorvos and echothiophate ages exclusively through O‐C bond cleavage. In contrast, isomalathion aging occurs through two pathways: the main product results from a P‐S bond cleavage and a minor product results from O‐C and/or S‐C bond cleavage. Supported by U.S. Army Research, Development & Engineering Command grant W911SR‐04‐C‐0019