Arita M, Sato Y, Arai H, Inoue K
Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Japan.
FEBS Lett. 1998 Oct 9;436(3):424-6. doi: 10.1016/s0014-5793(98)01176-4.
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.
α-生育酚（维生素E）是生物系统中一种重要的脂溶性抗氧化剂，由于清除活性氧，它会转化为α-生育醌。α-生育酚与肝细胞溶质中的α-生育酚转运蛋白（αTTP）结合，而α-生育醌则不结合。我们发现α-生育醌与一种分子量约为40 kDa的肝脏蛋白结合，该蛋白与αTTP不同。这种α-生育醌结合蛋白通过多步柱色谱法进一步纯化。最终制剂的十二烷基硫酸钠-聚丙烯酰胺凝胶电泳产生一条表观分子量为25 kDa的单条带，微量测序显示其与谷胱甘肽-S-转移酶（GST）相同。在α-生育醌存在的情况下，GST活性受到抑制，就像它被GST的其他非底物配体抑制一样，这证实了GST和α-生育醌直接相互作用。α-生育醌与GST结合，并可能像GST的其他非底物配体一样被转运到代谢部位或通过胆汁排泄。
