Differentiation between acetylcholinesterase and the organophosphate-inhibited form using antibodies and the correlation of antibody recognition with reactivation mechanism and rate.

Two types of polyclonal antibodies were generated from (a) a decapeptide sequence that includes the active site serine of acetylcholinesterase (anti-AChE10S) and (b) the identical decapeptide sequence phosphorylated at the active site serine of acetylcholinesterase (anti-AChE10SP). The anti-AChE10S antiserum was found to specifically recognize native, control, and vehicle-treated recombinant mouse AChE (rMoAChE) but did not recognize rMoAChE that was phosphorylated by the four organophosphate (OP) compounds tested. Conversely the anti-AChE10SP antiserum recognized phosphoserine rMoAChE that resulted from reaction with phosphorous oxychloride (POCl3) but did not recognize native or vehicle-treated rMoAChE. Anti-AChE10SP also did not recognize OP-AChE conjugates that resulted from the reaction of rMoAChE with other OP compounds that afford neutral or monoanionic phosphoserine groups thereby indicating a high specificity for a precise OP conjugate. Antisera recognition correlated well with the rates of enzyme inhibition, aging, and oxime-induced reactivation indicating these antisera can both quantify the extent and type of inhibition and also differentiate between select mechanisms of inhibition. The ability to discern mechanistic differences between native AChE and OP-AChE conjugates suggests that these antisera can be used to identify biomarkers of OP exposure in a mechanism-based approach.

Examination of cross-antigenicity of acetylcholinesterase and butyrylcholinesterase using anti-acetylcholinesterase antibodies.

Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) share a high degree of homology and overlap in several biochemical properties. This study aimed to compare and contrast the antigenic reactivity of AChE and BuChE with several polyclonal antibodies. We have performed a detailed analysis of AChE and BuChE enzymatic activities with different substrates and different inhibitors. Immunoassays conducted with polyclonal amino-terminus-specific anti-AChE antibodies were selective for mouse and electric eel AChE (EEAChE). Polyclonal carboxy-terminus-specific anti-AChE antibodies reacted with EEAChE and human BuChE, indicating an unexpected cross-reactivity. Polyclonal antisera raised against the whole AChE protein cross-reacted with horse BuChE, but not human BuChE. These data demonstrate that AChE and BuChE are immunologically similar.