Some properties of specific cholinesterase with particular reference to the mechanism of inhibition by diethyl p-nitrophenyl thiophosphate (E 605) and analogues

Abstract

The properties of a convenient prepn. of true cholinesterase from goat red cells were described. The available methods for the demonstration of reversibility were examined. The "dilution technic" of Nachman-sohn was modified and new methods devised. p-Nitrophenyl diethyl thiophosphate, p-nitrophenyl diethyl phosphate and di-isopropyl fluorophosphonate did not show any significant reversibility. 8-Quinolyl diethyl thiophosphate and nitrogen mustard were partly reversible. Benzoylcholine was demonstrated to be an inhibitor of specific cholinesterase. A technic was devised, using this property, to determine the affinity of inhibitors for cholinesterase. A maximum figure for the concn. of enzyme active centers was deduced.