Delta class glutathione S-transferase (TuGSTd01) from the two-spotted spider mite Tetranychus urticae is inhibited by abamectin

GSTs (Glutathione S-transferases) are known to catalyze the nucleophilic attack of sulfhydryl group reduced glutathione (GSH) on electrophilic centers xenobiotic compounds, including insecticides and acaricides. Genome analyses polyphagous spider mite herbivore Tetranychus urticae (two-spotted mite) revealed presence a set 32 genes that code for secreted proteins belonging GST family enzymes. To better understand role these in T. urticae, we have functionally characterized TuGSTd01. Moreover, modeled structure enzyme apo form, as well form with bound inhibitor. We demonstrated this protein is S-transferase can conjugate 1-chloro-2,4-dinitrobenzene (CDNB). tested TuGSTd01 activity range potential substrates such cinnamic acid, cumene hydroperoxide, allyl isothiocyanate; however, was unable process compounds. Using mutagenesis, showed putative active site variants S11A, E66A, S67A, R68A mutants, which were residues predicted interact directly GSH, no measurable activity, required enzymatic There several reports associate some acaricide resistance increased . However, found not able detoxify abamectin; fact, inhibits Ki = 101 μM. Therefore, suggest observed abamectin resistant field populations part compensatory feedback loop. In case, production relatively high concentration GSH cells allow maintain physiological functions despite acaricide.