title: Characterization of catalytic efficiency parameters of brain cholinesterases in tropical fish.
abstract: Brain cholinesterases from four fish (Arapaima gigas, Colossoma macropomum, Rachycentron canadum and Oreochromis niloticus) were characterized using specific substrates and selective inhibitors. Parameters of catalytic efficiency such as activation energy (AE), k(cat) and k(cat)/k(m) as well as rate enhancements produced by these enzymes were estimated by a method using crude extracts described here. Despite the BChE-like activity, specific substrate kinetic analysis pointed to the existence of only acetylcholinesterase (AChE) in brain of the species studied. Selective inhibition suggests that C. macropomum brain AChE presents atypical activity regarding its behavior in the presence of selective inhibitors. AE data showed that the enzymes increased the rate of reactions up to 10(12) in relation to the uncatalyzed reactions. Zymograms showed the presence of AChE isoforms with molecular weights ranging from 202 to 299 kDa. Values of k(cat) and k(cat)/k(m) were similar to those found in the literature.
authors: Laboratório de Enzimologia - LABENZ, Departamento de Bioquímica and Laboratório de Imunopatologia Keizo Asami - LIKA, Universidade Federal de Pernambuco, Campus Universitário, Recife, PE, 50670-901, Brazil, caiodias2@hotmail.com.
authors: Caio Rodrigo Dias
authors: CR
authors: de Assis
authors: Amanda Guedes
authors: AG
authors: Linhares
authors: Vagne Melo
authors: VM
authors: Oliveira
authors: Renata Cristina Penha
authors: RC
authors: França
authors: Juliana Ferreira
authors: JF
authors: Santos
authors: Marina
authors: M
authors: Marcuschi
authors: Elba Verônica Matoso Maciel
authors: EV
authors: Carvalho
authors: Ranilson Souza
authors: RS
authors: Bezerra
authors: Luiz Bezerra
authors: LB
authors: Carvalho
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002091:Butyrylcholinesterase / Q000378:metabolism*; D005399:Fishes / Q000145:classification* / Q000378:metabolism*; D013045:Species Specificity; D014329:Tropical Climate
chemical_list: D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase