SUBSTRATE SPECIFICITY AND INHIBITION STUDIES ON AFRICAN CATFISH (<i>Clarias gariepinus</i>) LIVER GLUTATHIONE S-TRANSFERASE

Abstract

The effect of some inhibitors of glutathione transferases was examined on a purified glutathione transferase from the liver of the African catfish (Clarias gariepinus). The ability of the enzyme to catalyze the conjugation of glutathione (GSH) with a variety of other compounds was also examined. The glutathione transferase (GST) from the African catfish was inhibited by all the compounds examined. Cibracron blue and triphenyltin chloride were the most potent inhibitors with I₅₀ (concentration of inhibitors causing 50% inhibition) of 0.0875μM and 0.0525μM respectively. The enzyme displayed broad substrate specificity. The enzyme was able to catalyze the conjugation of GSH with 1-chloro-2,4-dinitrobenzene (CDNB), ethacrynic acid , 4-nitrobenzylchloride, p-nitrophenylacetate and hydrogen peroxide. The results obtained from this work suggest that the glutathione transferase from the liver of African catfish might possibly belong to the Pi and Mu class of isoenzymes and that the enzyme is homodimeric.


Key Words: Glutathione transferase; African catfish; Clarias gariepinus; substrate specificity; isoenzyme(s)


Global Jnl Pure & Applied Science Vol.10(1) 2004: 179-182