RESUMO
Glutathione transferases (GSTs) are believed to be a major detoxification system in helminths. We describe the expression and functional analysis of EgGST, a cytosolic GST from Echinococcus granulosus, related to the Mu-class of mammalian enzymes. EgGST was produced as an enzymatically active dimeric protein (rEgGST), with highest specific activity towards the standard substrate 1-chloro-2,4-dinitrobenzene (CDNB; 2.5 micromol min(-1)mg(-1)), followed by ethacrynic acid. Interestingly, rEgGST displayed glutathione peroxidase activity (towards cumene hydroperoxide), and conjugated reactive carbonyls (trans-2-nonenal and trans,trans-2,4-decadienal), indicating that it may intercept damaging products of lipid peroxidation. In addition, classical GST inhibitors (cybacron blue, triphenylthin chloride and ellagic acid) and a number of anthelmintic drugs (mainly, hexachlorophene and rafoxanide) were found to interfere with glutathione-conjugation to CDNB; suggesting that they may bind to EgGST. Considered globally, the functional properties of rEgGST are similar to those of putative orthologs from Echinococcus multilcularis and Taenia solium, the other medically important cestodes. Interestingly, our results also indicate that differences exist between these closely related cestode GSTs, which probably reflect specific biological functions of the molecules in each parasitic organism.
Assuntos
Echinococcus granulosus/enzimologia , Glutationa Transferase/genética , Glutationa Transferase/metabolismo , Aldeídos/metabolismo , Animais , Derivados de Benzeno/metabolismo , Dimerização , Dinitroclorobenzeno/metabolismo , Echinococcus granulosus/genética , Inibidores Enzimáticos/farmacologia , Ácido Etacrínico/metabolismo , Glutationa Peroxidase/metabolismo , Glutationa Transferase/química , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por SubstratoAssuntos
Inibidores Enzimáticos/farmacologia , Peixes/metabolismo , Glutationa Transferase/efeitos dos fármacos , Fígado/efeitos dos fármacos , beta-Naftoflavona/farmacologia , Análise de Variância , Animais , Derivados de Benzeno/metabolismo , Brasil , Citosol/efeitos dos fármacos , Citosol/enzimologia , Dinitroclorobenzeno/metabolismo , Ácido Etacrínico/metabolismo , Glutationa Transferase/metabolismo , Fígado/enzimologia , Nitrobenzenos/metabolismo , Especificidade por SubstratoRESUMO
The interaction of three diuretics with bilirubin-albumin complexes was studied using the peroxidase assay, erythrocyte uptake, and sephadex gel filtration. On a molar basis, each diuretic was as potent or more potent than sulfisoxazole in displacing bilirubin from albumin. Furosemide and ethacrynic acid, when used at the recommended dosage (1 mg/kg), would probably not produce a significant increase in free bilirubin in most infants. Chlorothiazide could introduce a significant risk to jaundiced infants because of the higher dosage required.