David Shintani, Dean DellaPenna *
alpha-Tocopherol (vitamin E) is a lipid-soluble antioxidant synthesized only by photosynthetic organisms. alpha-Tocopherol is an essential component of mammalian diets, and intakes in excess of the U.S. recommended daily allowance are correlated with decreased incidence of a number of degenerative human diseases. Plant oils, the main dietary source of tocopherols, typically contain alpha-tocopherol as a minor component and high levels of its biosynthetic precursor, gamma-tocopherol. A genomics-based approach was used to clone the final enzyme in alpha-tocopherol synthesis, gamma-tocopherol methyltransferase. Overexpression of gamma-tocopherol methyltransferase in Arabidopsis seeds shifted oil compositions in favor of alpha-tocopherol. Similar increases in agricultural oil crops would increase vitamin E levels in the average U.S. diet.
Department of Biochemistry, Mail Stop 200, University of Nevada, Reno, NV 89557, USA. * To whom correspondence should be addressed. E-mail: email@example.com
Source: Science 11 December 1998: Vol. 282. no. 5396, pp. 2098 – 2100.