Methodological and biological aspects to be considered in cholinesterase reactivation techniques with oxime reagents

Monserrat, José María; Bianchini, Adalto


Kinetic and toxicological characteristics of fish (Odontesthes argentinensis) and crab (Callinectes sapidus) cholinesterases as well as methodological conditions to perform reactivation assays using pyridine 2-aldoxime (2-PAM) were established. According to kinetic and eserine sensitivity data, both cholinesterases can be considered as acetylcholinesterases. The concentration of eserine that inhibited 50% of enzyme activity IC50) was estimated as 15.9 10 8 and 4.6 10 8 M for crab and fish, respectively. For purified eel acetylcholinesterase (V-S type), it was estimated as 4.2 10 8 M. 2-PAM showed both to increase non-enzymatic hydrolysis of acetylthiocholine iodide and to inhibit activity of the acetylcholinesterases tested. The IC50 of 2-PAM for crab acetylcholinesterase (8.2 10 4 M) was significantly higher than that from O. argentinensis (2.5 10 4 M) or eel (2.0 10 4 M) acetylcholinesterase. Enzyme inhibition induced by 2-PAM showed to mask subtle inhibition due to malathion, suggesting that a previous characterization of 2-PAM inhibition must be done before its use in reactivation assays. assays.

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