Glutathione S-Transferases(GSTs) in Helicoverpa Armigera : Subcellular and Tissue Distribution of Activity, Developmental Changes and Induction of Allelochemicals

The Activity of GSTs in different tissues, developmental stages, subcellular fra ctions and induction by allelochemicals was determined in cotton bollworm, Helicoverpa armigera (Hübner). GSTs activity toward 1-chloro-2,4-dinitrobenze ne ( CDNB) was detected in the egg. It increased throughout the larval stages and up to the highest in the sixth instar larvae. The activity of GSTs from the larvae fed on artificial diet containing 50 mg/kg rutin or 2-tridecanone reach ed t he peak at the fifth instar. Enzyme activity was found in fat body, midgut, head and cuticle of the sixth instar larvae. The GSTs activity in fat body was the h ighest in above tissues. The Km values for CDNB conjugation varied with diff erent tissues, and the K m values of GSTs in the midgut was the lowest (8.5 mmol/L). The supernatant fraction possessed more than 90% of total activities of GSTs in the homogenate of midguts of the fifth instar larvae. The GSTs activity in microsome fraction from the third instar larvae induced by rutin was obviousl y lower than that fed only on artificial diet, but the enzyme activity in su pernatant fraction increased.