CHARACTERIZATION OF MONOCLONAL-ANTIBODIES THAT INHIBIT THE CATALYTIC ACTIVITY OF ACETYLCHOLINESTERASES

Monoclonal antibodies were generated against fetal bovine serum acetyl cholinesterase and fetal bovine serum acetylcholinesterase inhibited b y diisopropyl fluorophosphate or 7-(methyl ethoxyphosphinyloxy)-1-meth ylquinolinium iodide. Six monoclonal antibodies inhibited 70 to >98% o f the catalytic activity of fetal bovine serum acetylcholinesterase. I nhibition of serum acetylcholinesterase from several mammalia by four monoclonal antibodies showed broad cross-reactivity. In all cases, mon oclonal antibodies bound to the native form of acetylcholinesterases. None reacted with serum butyrylcholinesterases from various species. A lthough all monoclonal antibodies inhibited catalytic activity of acet ylcholinesterases, the site of interaction with acetylcholinesterase a ppeared to differ for several antibodies. Two types of acetylcholinest erase:monoclonal antibody complexes were formed: one between tetrameri c forms and another between catalytic subunits within the tetramer. Mo noclonal antibodies that inhibited acetylcholinesterase activity at >9 8% also considerably slowed binding of diisopropyl fluorophosphate and other organophosphorus compounds to the acetylcholinesterase:monoclon al antibody complex. Binding of these monoclonal antibodies to acetylc holinesterase influenced function of the enzyme's peripheral anionic s ite. None of the antibodies bound to the esteratic site of acetylcholi nesterase. Monoclonal antibodies caused changes in catalytic activity of acetylcholinesterase by interaction at a site remote from the catal ytic site, presumably at the entrance to the active site gorge.