Physiological significance of glutathione S-transferases.

The glutathione S-transferases represent a group of closely related soluble enzymes that seem geared to detoxification. These enzymes, which are most abundant in the liver but are found in most cells, catalyze the interaction between glutathione and a broad spectrum of electrophilic reactive drugs, carcinogens, and metabolites. In addition, a more speculative aspect of the detoxification role of these proteins is the covalent interaction between certain reactive carcinogen metabolites and the enzymes. Finally, as an aspect of their broad specificity, the transferases bind a broad spectrum of nonsubstrate ligands including bilirubin. On this basis a role in hepatic organic anion transport has been proposed for the transferases (previously known as Y protein or ligandin). It is now recognized that the transferases may affect net uptake by the liver by minimizing back diffusion. Much work remains to more precisely define the regulation and role(s) of this enzyme system in vivo.