Binding of alpha-tocopherylquinone, an oxidized form of alpha-tocopherol, to glutathione-S-transferase in the liver cytosol.
Alpha-tocopherol (vitamin E) is an important fat-soluble antioxidant in biological systems and, as a result of scavenging reactive oxygen, it is converted to alpha-tocopherylquinone. Alpha-tocopherol binds to alpha-tocopherol transfer protein (alphaTTP) in the liver cytosol, whereas alpha-tocopherylquinone does not. We found that alpha-tocopherylquinone binds to a liver protein with a molecular mass of about 40 kDa that is distinct from alphaTTP. This alpha-tocopherylquinone binding protein was purified further by multiple-step column chromatography. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of the final preparation yielded a single band with an apparent molecular mass of 25 kDa, which microsequencing revealed was identical to glutathione-S-transferase (GST). The GST activity was inhibited in the presence of alpha-tocopherylquinone, as it is by other non-substrate ligands for GST, confirming that GST and alpha-tocopherylquinone interact directly. Alpha-tocopherylquinone binds to GST and may be transported to the site of metabolism or excreted in the bile as other non-substrate ligands for GST.[1]References
- Binding of alpha-tocopherylquinone, an oxidized form of alpha-tocopherol, to glutathione-S-transferase in the liver cytosol. Arita, M., Sato, Y., Arai, H., Inoue, K. FEBS Lett. (1998) [Pubmed]
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