Atividade de Glutationa Peroxidase em frações mitocondriais e microssomais hepáticas de pacu, Piaractus mesopotamicus (Holmberg, 1887)

• Ano de defesa: 2010
• Autor(a) principal: Moes, Artur Pedro do Carmo
• Orientador(a): Bastos Neto, Jayme da Cunha
• Banca de defesa: Macedo, Jacyara Maria Brito , Paes, Márcia Cristina , Bastos, Vera Lucia Freire da Cunha
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade do Estado do Rio de Janeiro
• Programa de Pós-Graduação: Programa de Pós-Graduação em Biociências
• Departamento: Centro Biomédico::Instituto de Biologia Roberto Alcantara Gomes
• País: BR
• Palavras-chave em Português: Enzimas; Estresse Oxidante; ERO; GPX
• Palavras-chave em Inglês: Enzyme; Oxidative stress; ROS; GPX
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA
• Link de acesso: http://www.bdtd.uerj.br/handle/1/16298

Superoxide ions (O2˚ˉ), hydroxyl radicals (.OH) and hydrogen peroxide (H2O2) are three kinds of reactive of oxygen species (ROS) that tend to increase in cells under reduction of oxygen concentration or in cases of ischemia followed by reperfusion. If the quantities of these highly reactive chemical species are not kept bellow certain limits, the oxidative stress occurs, which leads to an impairment of the correct biochemical macromolecules functioning. This might end up with cellular death. ROS have been a target for several studies because they participate in pathologic processes of great importance, such as Alzheimer and Parkinson diseases. The pacu, Piaractus mesopotamicus (Holmberg, 1887), is a fish that is constantly submitted to hypoxia, so that it developed morphological and biochemical adaptations that permit it to resist to large changes of oxygen availability. However, it is still necessary to know the antioxidant enzymes that might be able to protect pacu cells against the oxidative stress. Glutathione peroxidases (GPX) are enzymes that reduce ROS as H2O2 and fatty acid peroxides. GPX activity from liver of rats has been described in three fractions: in citosol, anchored to the mitochondria membrane and associated to microsomes. Our objective was to assay glutathione peroxidase activity of the mitochondrial and microsomal hepatic fractions from pacu and determine some of its kinetic properties. There is more activity of GPX in microsomes than in mitochondria of pacu liver. The results show the existence of a very high activity of glutathione peroxidase in microsomal and mitochondrial hepatic fractions from pacu; higher than the ones already described in the same fractions from rat. This might be an indication that in an animal adapted to hypoxia the activity of GPX may be constitutively high. Enzymatic behavior is sigmoidal, and higher levels of GSH favors an increase of the maximum velocity of H2O2 reduction. The variation of velocity values in different concentrations of GSH shows that the increase in the concentrations of GSH favors the affinity of GPX by H2O2, and that the enzyme is most effective for reducing H2O2 at concentrations between 4 and 8 mM GSH.