505 Original article doi:10.12980/JCLM.3.2015J5-11 ©2015 by the Journal of Coastal Life Medicine. All rights reserved. Effect of ions on the activity of brain acetylcholinesterase from tropical fsh Caio Rodrigo Dias Assis 1* , Amanda Guedes Linhares 1 , Vagne Melo Oliveira 1 , Renata Cristina Penha França 1 , Juliana Ferreira Santos 2 , Elba Verônica Matoso Maciel Carvalho 3 , Ranilson Souza Bezerra 1 , Luiz Bezerra Carvalho Jr 1 1 Laboratory of Enzymology-LABENZ, Biochemistry Department and Laboratory of Immunopathology Keizo Asami, Federal University of Pernambuco, Recife-PE, Brazil 2 Academic Unit of Serra Talhada, Federal Rural University of Pernambuco, Serra Talhada-PE, Brazil 3 Laboratory of Glycoproteins, Biochemistry Department, Federal University of Pernambuco, Recife-PE, Brazil Journal of Coastal Life Medicine 2015; 3(7): 505-514 Journal of Coastal Life Medicine *Corresponding author: Caio Rodrigo Dias de Assis, Laboratory of Enzymology- LABENZ, Biochemistry Department and Laboratory of Immunopathology Keizo Asami, Federal University of Pernambuco, Recife-PE, Brazil. Tel: + 55 81 21268540 Fax: + 55 81 21268576 E-mail: caiodias2@hotmail.com Foundaton Project: Supported by Fundação de Apoio à Ciência e Tecnologia do Estado de Pernambuco (FACEPE) for financial support (Grant numbers: IBPG-1301- 2.08/08 FACEPE, IBPG-0523-2.08/11 FACEPE, BFP-0036-2.08/13 FACEPE and BFP-0111-2.08/13). 1. Introduction Acetylcholinesterase (AChE, EC 3.1.1.7) is a crucial enzyme for the development and functioning of the nervous system and play an important role in hematopoietic differentiation and neural development[1]. Its classical function is to modulate the nerve impulse through the hydrolysis of the neurotransmitter acetylcholine in the synaptic cleft[2]. AChE inhibition is the mechanism of action of organophosphorus and carbamate pesticides, as well as the mode of action of the drugs used in treatment of Alzheimer’s disease[2]. Therefore, AChE has been also used for monitoring these pesticide exposures in vivo[3] and in vitro[4] and even as a biocomponent of biosensors[5]. The investigation of AChE inhibitors and interfering substances is relevant to identify the usefulness of this enzyme as a tool in environmental and food monitoring[5-7]. Monitoring at biochemical level can specifically detect the presence of contaminants in the environment before they reach higher organizational levels[8]. Several studies reported inhibition of AChE activity by ions[9-11]. AChE activation by Ca 2+ , Mg 2+ , Al 3+ has also been reported[12,13]. Therefore, high content of these ions in water samples from rivers, lakes and other environments can influence the detection of anticholinesterasic pesticides. These findings must be taken into account when biosensors based on AChE activity are proposed to analyze pesticide presence under some environment conditions. This fact can lead to false positives or negatives and misinterpretations in the analysis of results. Cholinesterase inhibition has been assayed in several species, including aquatic organisms, since the event effectively ARTICLE INFO ABSTRACT Objective: To investigate the effect of ions on brain acetylcholinesterase (AChE; EC 3.1.1.7) activities from economic important fish [pirarucu, Arapaima gigas; tambaqui, Colossoma macropomum; cobia, Rachycentron canadum (R. canadum) and Nile tilapia, Oreochromis niloticus (O. niloticus)] comparing with a commercial enzyme from electric eel [Electrophorus electricus (E. electricus)]. Methods: The in vitro exposure was performed at concentrations ranging from 0.001 to 10 mmol/L (except for ethylene diamine tetraacetic acid; up to 150 mmol/L). Inhibition kinetics on R. canadum and O. niloticus were also observed through four methods (Michaelis-Menten, Lineweaver-Burk, Dixon and Cornish-Bowden plots) in order to investigate the type of inhibition produced by some ions. Results: Hg 2+ , As 3+ , Cu 2+ , Zn 2+ , Cd 2+ caused inhibition in all the species under study. Ca 2+ , Mg 2+ and Mn 2+ induced slight activation in R. canadum enzyme while Pb 2+ , Ba 2+ , Fe 2+ , Li + inhibited the AChE from some of the analyzed species. The lowest IC 50 and Ki values were estimated for E. electricus AChE in presence of Hg 2+ , Pb 2+ , Zn 2+ . Under our experimental conditions, the results for R. canadum and O. niloticus, As 3+ , Cu 2+ , Cd 2+ , Pb 2+ and Zn 2+ showed a non- competitive/mixed-type inhibition, while Hg 2+ inhibited the enzyme in a mixed/competitive- like manner. Conclusions: E. electricus AChE activity was affected by ten of fifteen ions under study showing that this enzyme could undergo interference by these ions when used as pesticide biosensor in environmental analysis. This hindrance would be less relevant for the crude extracts. Article history: Received 9 Feb 2015 Received in revised form 28 Feb 2015 Accepted 22 Apr 2015 Available online 9 Jun 2015 Keywords: Ions Acetylcholinesterase Biomarkers Fish journal homepage: www.jclmm.com