INHIBITION OF GLUTATHIONE TRANSFERASE TAU45 BY EOSIN

Objective: Glutathione transferases (GSTs) are multifunctional enzymes that catalyze the conjugation of glutathione (GSH) to electrophilic compounds, facilitating detoxication in living systems. In poplar trees, the tau class (GSTU) represents the largest group of GSTs, comprising 81 members. Despite their abundance, the physiological roles and inhibitors for these plant GSTs remain largely unexplored. This study investigates the inhibitory effect of eosin onPopulus trichocarpaGSTU45. GST inhibitors may be applied in agricultural biotechnology to overcome herbicide resistance in weeds, and enhance the efficacy of crop protection strategies.Material and Method: Poplar GSTU45 enzyme was heterologously expressed inEscherichia coli and purified using nickel sepharose affinity chromatography. The inhibitory effect of eosin on enzyme activity was performed spectrophotometrically with 1-chloro-2,4-dinitrobenzene (CDNB).Result and Discussion: Eosin exhibited moderate inhibition of GSTU45, with an IC50 value of 11.0 ± 1.0 µM against the conventional substrate CDNB. Inhibition kinetics revealed mixed-type inhibition with respect to GSH (Ki = 3.3 ± 0.4 µM) and competitive inhibition with respect to CDNB (Ki = 1.9 ± 0.1 µM), suggesting binding interactions at both the G- and H-sites. These findings provide new insights into the inhibition of tau GSTs and may aid in elucidating their physiological roles and guide their use in potential biotechnological applications.