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.
Arita
M
M
Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Japan.
Sato
Y
Y
Arai
H
H
Inoue
K
K
D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002845:Chromatography; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D017886:Durapatite; D004591:Electrophoresis, Polyacrylamide Gel; D005982:Glutathione Transferase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D051381:Rats; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism
D000975:Antioxidants; D010446:Peptide Fragments; D014810:Vitamin E; C002421:tocopherylquinone; D017886:Durapatite; D005982:Glutathione Transferase