Cloning and characterization of herbicide-degrading glutathione transferases from cicer arietinum

Abstract

GSTs are multifunctional enzymes that catalyze the conjugation of glutathione (GSH) to reactive electrophiles. These electrophiles are diverse and include important endogenous compounds, as well as xenobiotic chemicals, therefore GSTs play an important role in stress tolerance and herbicide detoxification. GSTs are usually active as a dimer of 24–29 kDa subunits. Each monomer of dimeric GSTs contains a G-site, at the N-terminal, capable of binding the GSH substrate and an H-site, at the C-terminal, that has xenobiotic compound-binding capabilities. Different classes of herbicides such as triazines, thiocarbamates, chloroacetanilides, diphenylethers, and aryloxyphenoxypropionates can be metabolized by GSTs. Herbicide tolerance in plants is based primarily on the differential ability of plant species to detoxify a herbicide, with the formation of a herbicide-GSH conjugate in the resistant but not in the susceptible species. The plant-specific phi and tau GSTs are primarily responsible for herbicide detoxification, showing class specificity in substrate preference. In present work, we report the cloning, kinetic and structural characterization of three members of the GST family from Cicer arietinum leaves (CaGSTs).