Hepatic glutathione S-transferases: identification by gel filtration and in vitro inhibition by organic anions.

In the gel filtration of 100,000 g rat liver supernatant, four major glutathione S-transferase activities, S-aryl-, S-epoxide-, S-aralykyl, and S-alkyltransferase, were identified as having an elution volume identical to that of fractions exhibiting either glutathione or sulfobromophthalein sodium binding. The organic anions, sulfobromophthalein sodium, indocyanine green, and bilirubin, were found to be competitive inhibitors of the four glutathione S-transferase activities. These findings indicate that the glutathione S-transferases bind organic anions, and as a group, have a similar molecular weight to a known organic anion-binding protein. It is proposed that these enzymes also serve nonenzymically as a group of binding proteins in the hepatic cytoplasmic transport of organic anions.