Glutathione S-transferase activity in human placenta

Glutathione S-transferase activity has been identified in human placenta cytosol. The soluble protein fraction subjected to isoelectric focusing was resolved into a single peak of activity towards 1-chloro-2,4-dinitrobenzene centred at pH 4.65. Gel filtration experiments indicated that the protein had a molecular weight of 60,000. There was no apparent binding of sulphobromophthalein to this protein. The placental glutathione S-transferase system was inhibited by some non-substrate anions but apparently not by bilirubin. Glutathione S-transferase activity was located in the cytosol of the chorial villi and to a lesser extent in the amnion; it appears in the early stages of pregnancy. This activity was not detected in the amniotic fluid.