Inhibitory Impact of Pesticides on Glutathione Reductase Activity in Bonito Fish (Sarda sarda)

Glutathione is a naturally occurring reducing agent that plays a critical role in protecting cells against oxidative stress. This protective function is facilitated by antioxidant enzymes with the inclusion of glutathione peroxidase and glutathione reductase (GR; EC 1.8.1.7). GR plays a key role in glutathione metabolism by continuously regenerating reduced glutathione (GSH), which is essential for combating oxidative stress within the cell. Therefore, GR activity is considered an important indicator of an organism’s defence capacity against environmental stressors, including heavy metals and pesticides. In this study, the GR enzyme was purified from the gill tissue of bonito and its biochemical response to pesticides was evaluated. After purification process, the optimum conditions for enzyme activity were determined as 200 mM KH₂PO₄ buffer at pH 6.5, and 2 mM NADPH as the substrate. The IC₅₀ values of the pesticides atrazine, oxamyl, and simazine were found to be 64.5 µM, 56.43 µM, and 53.45 µM, respectively. These findings suggest that GR enzyme could serve as a potential biomarker for assessing the toxicological impacts of environmental pollutants for aquatic organisms.