Glutathione-S-transferase (GST) activity from human term placenta and human fetal liver towards 1 -chloro-2,4-dinitrobenzene as the second substrate was significantly inhibited by the saturated fatty acids, stearic (SA) and palmitic (PA) acids and fatty acid esters, ascorbyl stearate (Asc-S) and ascorbyl palmitate (Asc-P). The nature of inhibition of human placental GST was competitive towards CDNB with Ki values of 3.1, 10.0, 13.5 and 18.5 μM for Asc-S, Asc-P, PA and SA, respectively. The inhibitory effect of Asc-S on human term placental GST was reversible. I50 values for Asc-S, Asc-P, SA and PA were 15, 45, 83 and 78 μM, respectively, for partially purified human fetal liver GSTs and 21, 6, 88 and 117 μM. respectively, for partially pure rat liver GSTs. The evidence suggests that Asc-S, Asc-P, SA and PA are potent inhibitors especially of the pi-class of GST.
- Ascorbyl esters
- Chemotherapeutic drug resistance
- Glutathione-S-transferase, pi-class