Abstract

The objective of this study was to examine the inhibitory effect of some heavy metals on the glutathione S-transferase (GST) enzyme, which is one of the major enzymes of glutathione metabolism purified from quail liver tissues. The quail liver GST enzyme was purified with 15.86 EU/mg specific activity, in a yield of 12.36% and 46.1 purification fold by ammonium sulfate precipitation and glutathione-agarose affinity chromatography. The molecular weight of subunits of the enzyme and the purity were determined by SDS-PAGE. In the characterization studies, the optimum pH of the GST enzyme was determined to be pH = 8.0 in Tris/HCl buffer. Optimum ionic strength was determined to be 140 mM in Tris/HCI buffer. Stable pH was found to be pH = 8.5 in Tris/HCl buffer. Optimum temperature was found to be 50 °C. KM and Vmax values for substrates 1-chloro-2,4-dinitrobenzene (CDNB) and GSH of the enzyme were determined to be KM 0.048 mM Vmax 0.479 EU/mL and KM 0.114 mM Vmax 0.672 EU/mL, respectively. In vitro inhibition effects of metal ions, including Ag+, Ni2+, Cd2+, Fe2+, Pb2+, Co2+ Zn2+, and Al3+, were investigated on the GST enzyme activity. The results showed that Ag+, Cd2+, Ni2+ Zn2+, and Al3+ metal ions inhibited GST enzyme (IC50 values 0.239, 0.250, 0.265, 0.320, 0.594 mM, respectively), while Fe2+, Pb2+, and Co2+ metal ions activated the enzyme. Finally, Ki values and inhibition types for these substances were determined by Lineweaver-Burk graphs.

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