A Kinetic Study on the Inhibition of Hen Brain Neurotoxic Esterase by Mipafox

A direct method of assaying neurotoxic esterase (NTE) activity, using 4-nitrophenyl valerate, has been described. The technique was used to determine the bimolecular rate (ki), phosphorylation (k2), and affinity (Kd) constants for the reaction of hen brain microsomal NTE with mipafox. Results indicate that the new technique for assaying NTE makes detailed kinetic studies of NTE inhibition possible. The affinity and phosphorylation constants, Kd and k2, for the reaction of hen brain microsomal NTE with mipafox, were found to be 6.72 x 10(-5) M and 3.23 min-1, respectively. The bimolecular rate constant (ki) for this reaction was obtained by interpreting the results according to two different linear equations. The obtained values for ki by these interpretations were 4.8 x 10(4) and 4.0 x 10(4) M-1 min-1, respectively.