Plant glutathione S-transferases: enzymes with multiple functions in sickness and in health

Glutathione S-transferases (GSTs) are abundant proteins encoded by a highly divergent, ancient gene family. Soluble GSTs form dimers, each subunit of which contains active sites that bind glutathione and hydrophobic ligands. Plant GSTs attach glutathione to electrophilic xenobiotics, which tags them for vacuolar sequestration. The role of GSTs in metabolism is unclear, alt hough their complex regulation by environmental stimuli implies that they h ave important protective functions. Recent studies show that GSTs catalyse glutathione-dependent isomerizations and the reduction of toxic organic hyd roperoxides. GSTs might also have non-catalytic roles as carriers for phyto chemicals.