| Title : Acetylcholinesterase of mangrove oyster Crassostrea rhizophorae: A highly thermostable enzyme with promising features for estuarine biomonitoring - de Souza_2018_Aquat.Toxicol_197_109 |
| Author(s) : de Souza PR , de Souza KS , de Assis CRD , de Araujo MC , Silva KCC , de Fatima Xavier da Silva J , Ferreira ACM , da Silva VL , Adam ML , de Carvalho LB, Jr. , de Souza Bezerra R |
| Ref : Aquat Toxicol , 197 :109 , 2018 |
|
Abstract :
Enzyme biomarkers from several aquatic organisms have been used for assessing the exposure to contaminants at sublethal levels. Amongst them, the cholinesterases are commonly extracted from several organisms to evaluate/measure organophosphate and carbamate neurotoxic effects. Acetylcholinesterase (AChE; EC 3.1.1.7) is an enzyme of the group of serine esterases that acts on the hydrolysis of the neurotransmitter acetylcholine allowing the intermittence of the nerve impulses responsible for the neuronal communication. This enzyme is the main target for the action of some pesticides and the inhibition of its activity in bivalve mollusks may be used as biomarker due to their filter-feeding habit. In this context, the present study aimed to characterize physicochemical and kinetic parameters of the AChE extracted from gills and viscera of the oyster Crassostrea rhizophorae and investigate the in vitro effect of pesticides (dichlorvos, diazinon, chlorpyrifos, methyl-parathion, temephos, carbaryl, carbofuran, aldicarb, diflubenzuron and novaluron) in search for assessing its potential as biomarker. Specific substrates and inhibitors evidenced the predominance of AChE in both tissues. The optimum pH found for gills and viscera AChE were 8.0 and 8.5, respectively. The maximum peak of activity occurred at 70 degrees C for gill AChE and 75 degrees C for viscera AChE. The enzymes of both tissues presented remarkable thermostability. The Michaelis-Menten constant for both enzymes were 1.32+/-0.20mM for gills and 0.43+/-0.12mM for viscera. The Vmax values for gills and viscera were 53.57+/-1.72 and 27.71+/-1.15mU/mg, respectively. The enzymes were able to reduce the activation energy to 9.75kcalmol(-1) (gills) and 11.87kcalmol(-1) (viscera) obtaining rate enhancements of 3.57x10(5) and 1.01x10(4), respectively, in relation to non-catalyzed reactions. Among the pesticides under study, the carbamates carbaryl and carbofuran exerted the strongest inhibitory effects on the enzyme activity achieving important degrees of inhibition at concentrations below national and international current regulations. The first observation of the effects of benzoylurea pesticides (diflubenzuron and novaluron) on AChE from mollusks is reported here. The gills AChE of C. rhizophorae showed potential to be specific biomarker for the carbamate carbaryl while the viscera AChE showed it for carbofuran. According to their features, these enzymes may be proposed as promising tools for estuarine monitoring as well as biocomponent of biosensor devices. |
| PubMedSearch : de Souza_2018_Aquat.Toxicol_197_109 |
| PubMedID: 29462762 |
de Souza PR, de Souza KS, de Assis CRD, de Araujo MC, Silva KCC, de Fatima Xavier da Silva J, Ferreira ACM, da Silva VL, Adam ML, de Carvalho LB, Jr., de Souza Bezerra R (2018)
Acetylcholinesterase of mangrove oyster Crassostrea rhizophorae: A highly thermostable enzyme with promising features for estuarine biomonitoring
Aquat Toxicol
197 :109
de Souza PR, de Souza KS, de Assis CRD, de Araujo MC, Silva KCC, de Fatima Xavier da Silva J, Ferreira ACM, da Silva VL, Adam ML, de Carvalho LB, Jr., de Souza Bezerra R (2018)
Aquat Toxicol
197 :109