Identification of a developmentally and hormonally regulated Delta-Class glutathione S-transferase in rice moth Corcyra cephalonica.
ABSTRACT Glutathione S-transferases (GSTs) are a large family of multifunctional enzymes, known for their role in cellular detoxification. Here we report a cytosolic GST with optimal activity at alkaline pH (8.3) from the visceral fat body of late-last instar (LLI) larvae of a lepidopteran insect rice moth Corcyra cephalonica. All previously known GSTs are active between pH 6.0 to 6.5. Purification and characterization revealed the Corcyra cephalonica GST (CcGST) as a 23-kDa protein. HPLC and 2D analysis showed a single isoform of the protein in the LLI visceral fat body. Degenerate primer based method identified a 701-nucleotide cDNA and the longest open reading frame contained 216 amino acids. Multiple sequence and structural alignment showed close similarity with delta-class GSTs. CcGST is present mainly in the fat body with highest activity at the late-last instar larval stage. Juvenile hormone (JH) negatively inhibits the CcGST activity both ex vivo and in vivo. We speculate that high expression and activity of CcGST in the fat body of the late-last instar larvae, when endogenous JH titer is low may have role in the insect post-embryonic development unrelated to their previously known function.
- Electrophoresis. 01/1987; 8:93 - 99.
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ABSTRACT: Bacterial dichloromethane dehalogenases catalyze the glutathione-dependent hydrolysis of dichloromethane to formaldehyde and are members of the enzyme superfamily of glutathione S-transferases involved in the detoxification of electrophilic compounds. Numerous protein engineering studies have addressed questions pertaining to the substrate specificity, the reaction mechanism, and the kinetic pathway of glutathione S-transferases. In contrast, the molecular determinants for binding of the glutathione cofactor have been less well investigated. Dichloromethane dehalogenases from Hyphomicrobium sp. DM2 and Methylobacterium sp. DM4 displayed significantly different affinities for glutathione, but not for the dichloromethane substrate. The sequence of dcmA, the dichloromethane dehalogenase gene from strain DM2, was determined and featured a single base difference from the previously determined sequence of dcmA from strain DM4. This base change resulted in a single amino acid difference in the corresponding proteins at sequence position 27. Site-directed variants of the homologous dichloromethane dehalogenase from Methylophilus sp. DM11 (56% amino acid identity) at the corresponding residue in the protein sequence provided further evidence that this residue selectively modulated the dependence of dichloromethane dehalogenase activity on glutathione.Biochemical and Biophysical Research Communications 10/1997; 238(2):452-456. · 2.41 Impact Factor
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ABSTRACT: Oxylipins play important roles in stress signaling in plants. The compound 12-oxophytodienoic acid (cis-OPDA) is an early biosynthetic precursor of jasmonic acid (JA), the key phytohormone orchestrating the plant anti-herbivore defense. When consumed by feeding Lepidopteran larvae, plant-derived cis-OPDA suffers rapid isomerization to iso-OPDA in the midgut and is excreted in the frass. Unlike OPDA epimerization (yielding trans-OPDA), the formation of iso-OPDA is enzyme-dependent, and is catalyzed by an inducible glutathione transferase (GSTs) from the larval gut. Purified GST fractions from the gut of Egyptian cotton leafworm (Spodoptera littoralis) and cotton bollworm (Helicoverpa armigera) both exhibited strong OPDA isomerization activity, most likely via transient formation of a glutathione-OPDA conjugate. Out of 16 cytosolic GST proteins cloned from the gut of cotton bollworm larvae and expressed in E. coli, only one catalyzed the OPDA isomerization. The biological function of the double bond shift might be seen in an inactivation of cis-OPDA, similar to the inactivation of prostaglandin A1 to prostaglandin B1 in mammalian tissue. The enzymatic isomerization is particularly widespread among generalist herbivores that have to cope with various amounts of cis-OPDA in their spectrum of host plants.Proceedings of the National Academy of Sciences 09/2009; 106(38):16304-9. · 9.74 Impact Factor