alpha-Tocopherol inhibits human glutathione S-transferase pi

alpha -Tocopherol is the most important fat-soluble, chain-breaking antioxi dant. It is known that interplay between different protective mechanisms oc curs. GSTs can catalyze glutathione conjugation with various electrophiles, many of which are toxic. We studied the influence of alpha -tocopherol on the activity of the cytosolic pi isoform of GST. alpha -Tocopherol inhibits glutathione S-transferase pi in a concentration-dependent manner, with an IC50-value of 0.5 muM. At alpha -tocopherol additions above 3 muM there was no GST pi activity left. alpha -Tocopherol lowered the V-max values, but d id not affect the K-m for either CDNB or GSH. This indicates that the GST p i enzyme is noncompetitively inhibited by alpha -tocopherol. An inhibition of GST pi by alpha -tocopherol may have far-reaching implications for the a pplication of vitamin E. (C) 2001 Academic Press.