Characterization of catalytic efficiency parameters of brain cholinesterases in tropical fish
2014
de Assis, Caio Rodrigo Dias | Linhares, Amanda Guedes | Oliveira, Vagne Melo | França, Renata Cristina Penha | Santos, Juliana Ferreira | Marcuschi, Marina | Maciel Carvalho, Elba Verônica Matoso | Bezerra, Ranilson Souza | Carvalho, Luiz Bezerra, Jr
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 10¹² 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.
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