Impacts of some metal ions on glutathione s-transferase in the liver of Chalcalburnus tarichi: an endemic species of Lake Van

Authors: MUHAMMET SERHAT ÖZASLAN, MEHMET ÇİFTCİ

Abstract: Glutathione-S-transferase (GSTs) is a multifunctional enzyme that provides homeostasis by catalyzing the first step of the formation of mercapturic acid, the end product in detoxification metabolism. They can prevent reactive electrophilic compounds from harming the body by covalently binding the same type of compounds to each other. In this study, we determined the in vitro inhibitory effects of metal ions such as Cu²⁺, Cd²⁺, Ag⁺, and Co²⁺ on GST enzyme activity. For this aim, GST was purified from C. tarichi Pallas liver with 37.36% yield and 29.304 EU/mg specific activity using the chromatographic method. The V_max values of liver GST were determined for CDNB and GSH to be 1.245 and 0.562 EU/mL, respectively, and the K_m values were found 0.89 and 0.06 mM, respectively, using the Lineweaver?Burk plot. The effects of the metal ions at different concentrations on in vitro GST activity were studied. The IC₅₀ values were determined for Cu⁺², Cd⁺², Ag⁺, and Co⁺² as 0.163, 0.235, 0.00021, and 0.446 mM, respectively. The Ki constants were determined as 0.049 ± 0.009, 0.117 ± 0.031, 0.002 ± 0.0007, and 0.893 ± 0.3 mM, respectively. Ag⁺ showed the best inhibitory effect among the studied metal ions. Cd²⁺, Cu²⁺ and Co²⁺ showed a competitive inhibition mechanism, while Ag⁺ was noncompetitive.

Keywords: Lake Van fish, purification, glutathione S-transferase, inhibition

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