Assis_2012_Sci.Total.Environ_441C_141

Monitoring of pesticides based on acetylcholinesterase AChE EC 3.1.1.7 inhibition in vitro avoids interference of detoxification defenses and bioactivation of some of those compounds in non-target tissues Moreover environmental temperature age and stress are able to affect specific enzyme activities when performing in vivo studies Few comparative studies have investigated the inter-specific differences in AChE activity in fish Screening studies allow choosing the suitable species as source of AChE to detect pesticides in a given situation Brain AChE from the tropical fish pirarucu Arapaima gigas cobia Rachycentron canadum and Nile tilapia Oreochromis niloticus were characterized and their activities were assayed in the presence of pesticides the organophosphates dichlorvos diazinon chlorpyrifos temephos tetraethyl pyrophosphate TEPP and the carbamates carbaryl and carbofuran Inhibition parameters IC(50 and Ki for each species were found and compared with commercial AChE from electric eel Electrophorus electricus Optimal pH and temperature were found to be 8.0 and 35-45 degrees C respectively A gigas AChE retained 81 of the activity after incubation at 50 degrees C for 30min The electric eel enzyme was more sensitive to the compounds mainly carbofuran IC(50 of 5nM excepting the one from A gigas IC(50 of 9nM under TEPP inhibition These results show comparable sensitivity between purified and non-purified enzymes suggesting them as biomarkers for organophosphorus and carbamate detection in routine environmental and food monitoring programs for pesticides.