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Gene Found for Keeping Citrus Juice Sweet / August 24, 1998 / News from the USDA Agricultural Research Service

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Gene Found for Keeping Citrus Juice Sweet

By Kathryn Barry Stelljes
August 24, 1998

Fruit juice of the future could stay sweeter longer--and might be even more nutritious. That's because scientists now have isolated the gene for a key citrus enzyme. Shin Hasegawa, a biochemist with USDA's Agricultural Research Service in Albany, Calif., presented the findings yesterday at the American Chemical Society's 216th Annual Meeting in Boston.

Sweet, fresh-squeezed citrus juice can turn bitter after only a few hours. But a decade ago, Hasegawa discovered that oranges, grapefruits and other citrus contain an enzyme called limonin glucosyltranferase (LGT). LGT converts the bittering agents into tasteless compounds called limonoid glucosides.

Now researchers at the Japanese National Institute of Fruit Tree Science, who are collaborating with ARS, have determined the genetic sequence of the enzyme. The team hopes to use the genetic information to produce orange trees that bear fruit with more limonoid glucosides. That would mean citrus juice that wouldn't turn bitter.

Another potential benefit of limonoid glucosides: university studies suggest they may help prevent tumor formation. At Baylor University College of Dentistry in Dallas, limonoids inhibited experimentally induced oral cancer tumors in hamsters. In a study at the University of Western Ontario, Canada, the compounds inhibited proliferation of human breast cancer cells in mice and cell culture. ARS provided the purified limonoid glucosides for these experiments.

ARS and the Japanese researchers are applying for patent protection of the gene. Earlier this year, ARS and a private Japanese company were awarded a patent on a commercial process for extracting the limonoid glucosides from citrus fruit.

Scientific contact: Shin Hasegawa, ARS Process Chemistry and Engineering Research Unit, Western Regional Research Center, Albany, CA 94710, phone (510) 559-5819, fax (510) 559-5963, shinh@pw.usda.gov. From August 22-26, Dr. Hasegawa can be reached at Copley Square Hotel, phone (617) 536-9000, fax (617) 236-0351 or through the ACS Press Room, phone 617-954-3476.

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