Separation of two forms of neuropathy target esterase in the soluble fraction of the hen sciatic nerve

Abstract

Neuropathy target esterase (NTE) activity is operatively defined in this paper as the phenyl valerate esterase activity resistant to 40 μM paraoxon but sensitive to 250 μM mipafox. Molecular exclusion column chromatography with Sephacryl S-300 of the soluble (S) fraction from chick sciatic nerve demonstrated two NTE activity peaks. The first eluted with the front, thus indicating a mol. wt. of over 700 kDa (peak V 0), while the second peak eluted with kd = 0.36, suggestting a mol. wt. of about 100 kDa. The curve of total phenyl valerate (PVase) activity inhibition with paraoxon (0.19–200 μM) shows that at a concentration of 40 μM the esterases highly sensitive to paraoxon are inhibited in the V 0 and 100-kDa peaks. The NTE activity in these two peaks in turn represented 31% and 44% of the 40 μM paraoxon resistant activity, respectively. The mipafox inhibition curves (1.0μ-250 μM) revealed different sensitivities to mipafox, with I 50 values ( t = 30 min) of approximately 1.47 and 63 μM, for V 0 and 100-kDa peaks respectively. Mipafox sensitivity of the V 0 and 100-kDa peaks correlates with the two components, that had been deduced from the kinetic properties of the S-fraction.