Publications

• Increased alpha-tocotrienol content in seeds of transgenic rice overexpressing Arabidopsis gamma-tocopherol methyltransferase.

  Zhang G.Y., Liu R.R., Xu G., Zhang P., Li Y., Tang K.X., Liang G.H., Liu Q.Q.

  Vitamin E comprises a group of eight lipid soluble antioxidant compounds that are an essential part of the human diet. The α-isomers of both tocopherol and tocotrienol are generally considered to have the highest antioxidant activities. γ-tocopherol methyltransferase (γ-TMT) catalyzes the final st ... >> More

  Vitamin E comprises a group of eight lipid soluble antioxidant compounds that are an essential part of the human diet. The α-isomers of both tocopherol and tocotrienol are generally considered to have the highest antioxidant activities. γ-tocopherol methyltransferase (γ-TMT) catalyzes the final step in vitamin E biosynthesis, the methylation of γ- and δ-isomers to α- and β-isomers. In present study, the Arabidopsis γ-TMT (AtTMT) cDNA was overexpressed constitutively or in the endosperm of the elite japonica rice cultivar Wuyujing 3 (WY3) by Agrobacterium-mediated transformation. HPLC analysis showed that, in brown rice of the wild type or transgenic controls with empty vector, the α-/γ-tocotrienol ratio was only 0.7, much lower than that for tocopherol (~19.0). In transgenic rice overexpressing AtTMT driven by the constitutive Ubi promoter, most of the γ-isomers were converted to α-isomers, especially the γ- and δ-tocotrienol levels were dramatically decreased. As a result, the α-tocotrienol content was greatly increased in the transgenic seeds. Similarly, over-expression of AtTMT in the endosperm also resulted in an increase in the α-tocotrienol content. The results showed that the α-/γ-tocopherol ratio also increased in the transgenic seeds, but there was no significant effect on α-tocopherol level, which may reflect the fact that γ-tocopherol is present in very small amounts in wild type rice seeds. AtTMT overexpression had no effect on the absolute total content of either tocopherols or tocotrienols. Taken together, these results are the first demonstration that the overexpression of a foreign γ-TMT significantly shift the tocotrienol synthesis in rice, which is one of the world's most important food crops. << Less

  Transgenic Res 22:89-99(2013) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Characterization of gamma-tocopherol methyltransferases from Capsicum annuum L and Arabidopsis thaliana.

  Koch M., Lemke R., Heise K.P., Mock H.P.

  Tocopherols are essential micronutrients in human and animal nutrition due to their function as lipophilic antioxidants. They are exclusively synthesized by photosynthetic organisms including higher plants. Despite the attributed beneficial health effects and many industrial applications, research ... >> More

  Tocopherols are essential micronutrients in human and animal nutrition due to their function as lipophilic antioxidants. They are exclusively synthesized by photosynthetic organisms including higher plants. Despite the attributed beneficial health effects and many industrial applications, research on the tocopherol biosynthetic pathway and its regulation in plants is still limited. In the work presented here we performed a detailed biochemical characterization of a gamma-tocopherol methyltransferase (gamma-TMT) from Arabidopsis thaliana and of a gamma-TMT purified from Capsicum annuum fruits, a tissue with high accumulation of tocopherols. The biochemical characteristics of both enzyme preparations were remarkably similar including substrate specificities. Both enzymes converted delta- and gamma- into beta- and alpha-tocopherol, respectively, but beta-tocopherol was not accepted as a substrate, pointing to a specific methylation at the C(5)-position of the tocopherol aromatic head group. A kinetic analysis performed with the Arabidopsis enzyme was consistent with an iso-ordered bi-bi type reaction mechanism. Our results emphasize the role of gamma-TMT in regulating the spectrum of accumulated tocopherols in plants. << Less

  Eur J Biochem 270:84-92(2003) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.