Industrial and agricultural processes have brought about the pollution of aquatic systems, and this situation in the water had adverse effects on human health. In order to reduce these negative effects, all mammalian and aquatic species have a defense system. One of these antioxidant systems is the glutathione S-transferase enzyme group, which has detoxification activity against ROS produced by organic pollutants and heavy metals. In this study, the effects of some pesticides and heavy metal ions on the GST enzyme activity purified kidney tissue of the Lake Van fish (C. Tarichii) was analyzed. Firstly, the purification process was carried out as homogenate preparation and glutathione-agarose affinity technique. SDS-PAGE was carried out to check the enzyme purity. The enzyme was obtained in 89% yield (335-fold) with 27.8-specific activity , and kinetic constants was determined for the enzyme; Km for GSH substrate: 0.429 mM Vmax for GSH substrate: 0.207 EU/mL-1; Km for CDNB substrate: 0.276 mM, Vmax for CDNB substrate: 0.161EU/mL-1. Effects of Met-Hg, Fe3+ Cr3+ , Cu2+, Mg2+, Zn2+, atrazine, methomyl ,and dinicanozole were studied on the activity of the purified enzyme and the IC50 values were determined as 34.5 mM, 10 μM, 1.5 μM, 2.4 μM, 63 μM, 0.15 mM, 9.8 μM, 2.67 μM , and 1.3 μM, respectively.