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Chromatographic Discrimination of Soluble Neuropathy Target Esterase Isoenzymes and Related Phenyl Valerate Esterases from Chicken Brain, Spinal Cord, and Sciatic Nerve
Author(s) -
Escudero M. A.,
Céspedes M. V.,
Vilanova E.
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.68052170.x
Subject(s) - chemistry , paraoxon , sciatic nerve , chromatography , esterase , fractionation , size exclusion chromatography , molecular mass , microsome , enzyme , biochemistry , acetylcholinesterase , anatomy , medicine
Neuropathy target esterase (NTE) activity is operatively defined in this work as the phenyl valerate esterase (PVase) activity resistant to 40 µ M paraoxon but sensitive to 250 µ M mipafox. Gel filtration chromatography with Sephacryl S‐300 of the soluble fraction from spinal cord showed two PVase peaks containing NTE activity (S‐NTE1 and S‐NTE2). The titration curve corresponding to inhibition by mipafox was studied over the 1–250 µ M range, in the presence of 40 µ M paraoxon. The data revealed that S‐NTE1 and S‐NTE2 have different sensitivities to mipafox with I 50 (30 min) values of 1.7 and 19 µ M , respectively. This was similar to the pattern observed in the soluble fraction from sciatic nerve with two components ( V o peak, or S‐NTE1; and 100‐K peak, or S‐NTE2) with different sensitivity to mipafox. However, in the brain soluble fraction, only the high‐molecular‐mass (>700‐kDa) peak or S‐NTE1 was obtained. It showed an I 50 of 5.2 µ M in the mipafox inhibition curve. The chromatographic profile was different on changing the pH in the subcellular fractionation. When the homogenized tissue was centrifuged at pH 6.8, the V o peak activity decreased in the soluble fraction from these nerve tissues. This suggests that the V o peak could be related to materials partly solubilized from membranes at higher pH. The chromatographic pattern and mipafox sensitivity suggest that the different tissues have a different NTE isoform composition. S‐NTE2 should be a different entity than S‐NTE1 and particulate NTE. The potential role of soluble forms in the mechanism of initiation or promotion of neuropathy due to organophosphorus remain unknown.