PURIFICATION AND PARTIAL CHARACTERIZATION OF GLUTATHIONE S-TRANSFERASES FROM INSECTICIDE-RESISTANT AND LINDANE-INDUCED SUSCEPTIBLE SPODOPTERA-LITTORALIS (BOISD) LARVAE

Cytosolic GST activity was followed after a single topical application of a non-lethal dose of lindane to fourth instar larvae of a suscepti ble strain of Spodoptera littoralis (Boisd.). The induction reached it s peak 8 h after treatment for 1-chloro-2,4-dinitrobenzene (CDNB) conj ugating GSTs (1.5-fold), and 12 h after the treatment for 1,2-dichloro -4-nitrobenzene (DCNB) conjugating enzymes (1.3-fold). CDNB conjugatin g GST activity in an insecticide-resistant strain of S. littoralis was twice that measured in the non-induced susceptible larvae. No signifi cant difference was observed with DCNB. GSTs of both larvae were purif ied by affinity chromatography using a glutathione-agarose column, whi ch resulted in a 30-fold purification and a yield of 50-70%. Purified GSTs were characterized using CDNB as the substrate. Apparent K(m) and V(max) values calculated for CDNB and reduced glutathione (GSH) were significantly different between the resistant strain and the susceptib le one, whether induced by lindane or not. The lindane treatment modif ied only K(m) values for CDNB and GSH in susceptible larvae. Monodimen sional SDS-PAGE of GSTs purified from both strains revealed a large ba nd of 27 kDa apparent molecular weight.