SEPARATION OF 2 FORMS OF NEUROPATHY TARGET ESTERASE IN THE SOLUBLE FRACTION OF THE HEN SCIATIC-NERVE

Neuropathy target esterase (NTE) activity is operatively defined in th is paper as the phenyl valerate esterase activity resistant to 40 mu M paraoxon but sensitive to 250 mu M mipafox. Molecular exclusion colum n chromatography with Sephacryl S-300 of the soluble (S) fraction from chick sciatic nerve demonstrated two NTE activity peaks. The first el uted with the front, thus indicating a mel. wt, of over 700 kDa (peak V-0), while the second peak eluted with kd = 0.36, suggestting a mel. wt. of about 100 kDa. The curve of total phenyl valerate (PVase) activ ity inhibition with paraoxon (0.19-200 mu M) shows that at a concentra tion of 40 mu M the esterases highly sensitive to paraoxon are inhibit ed in the V-0 and 100-kDa peaks. The NTE activity in these two peaks i n turn represented 31% and 44% of the 40 mu M paraoxon resistant activ ity, respectively, The mipafox inhibition curves (1.0-250 mu M) reveal ed different sensitivities to mipafox, with I-50 values (t = 30 min) o f approximately 1.47 and 63 mu M, for V-0, and 100-kDa peaks respectiv ely. 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.