Properties of partly preinhibited hen brain neuropathy target esterase

NTE inhibitors cause different toxicological consequences (protection, induction or potentiation/promotion of neuropathy) depending on the order of dosing. These effects might be explained in terms of several phosphorylable sites with 'allosteric irreversible' behaviour. Brain neuropathy target esterase (NTE) has been preinhibited with phenylmethylsulphonyl fluoride (PMSF) (0, 5, 10, 15, 30 and 60 microM) or with diisopropylphoshoro fluoridate (DFP) (0, 0.2, 0.5, and 1 microM) at 37 degrees C for 30 min. After washing by centrifugation, tissues were then reinhibited with a range of PMSF (0 to 80 microM) or DFP (0 to 1 microM) concentrations. The slopes of the inhibition curves (log % activity vs. concentration) of pretreated tissues were identical to those of the non-pretreated tissues, with non-distinguishable I50 values. It is concluded that allosteric effects are not likely to be involved in membrane-bound NTE of hen brain.