title: Reactivation and aging of diphenyl phosphoryl acetylcholinesterase.
abstract: Acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) is readily in hibited by 10(-5) M diphenylphosphorochloridate even though the inhibitor hydrolyzes in a few seconds. The fluoridate is a much weaker inhibitor. The inhibited enzyme, diphenyl phosphoryl enzyme spontaneously recovers only about 50% of its activity with a half time of about 17 min at pH 7.0 and 6 min at pH 8.0. The fact that only 50% of the original activity returns is due to aging. The rates of reactivation and aging can be very greatly increased by a few percent of an organic solvent. Depending on the solvent even 1% may increase the rates by a factor of 5 or 6. The highest increase in rate was 70-fold. Quaternary NH+4 also increases the rates. Organic solvents and NH+4 also accelerate the reactivation of the much more stable diethyl phosphoryl enzyme derivative.
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004355:Drug Stability; D004524:Eels; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D009943:Organophosphorus Compounds / Q000494:pharmacology; D011485:Protein Binding; D012997:Solvents; D013997:Time Factors
chemical_list: D009943:Organophosphorus Compounds; D012997:Solvents; D000110:Acetylcholinesterase; D004121:Dimethyl Sulfoxide