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Morphing Plant Enzymes for use in oil fabrication



http://www.pubaf.bnl.gov/pr/bnlpr111298.html
Scientists Report First "Morphing" of Plant Enzyme Function

NOVEMBER 12, 1998

                     BROOKHAVEN, CARNEGIE SCIENTISTS REPORT
                   FIRST "MORPHING" OF PLANT ENZYME FUNCTION

 UPTON, NY - In a transformation worthy of Hollywood special effects,
 biochemists have for the first time "morphed" a plant enzyme, turning it into
 another enzyme with a different function, through genetic manipulation.

 The achievement advances the prospects of "designer" plants for renewable
 industrial raw materials, fuel and food. It also sheds new light on how plant
 enzymes evolved to perform different functions.

 The team of scientists from the U.S. Department of Energy's Brookhaven
 National Laboratory and the Carnegie Institution of Washington's Stanford,
 California, campus reports its accomplishment in today's issue of Science .

 "We have shown that it is possible to change an enzyme's function dramatically
 by tweaking its structure just slightly," said John Shanklin, who co-led the
 research team. "Nature has been doing this for eons through mutation; our
 experiment shows how such changes might come about and what their end result
 is."

 DOE's Director of the Office of Science, Martha Krebs, commented, "This is not
 only a discovery of fundamental scientific significance, but it clearly
 demonstrates a pathway to develop an alternative, biologically-based source
 for many oils used in industry which currently depend upon petroleum for their
 production."

 Shanklin and his colleagues worked with enzymes called desaturases and
 hydroxylases, taken from different species of related cruciferous plants.

 Both enzymes perform important tasks. Desaturase converts plant molecules
 called fatty acids from straight to bent, by turning single chemical bonds
 into double ones. Hydroxylase adds hydroxy groups to the fatty acids'
 structure.

 These simple chemical changes can make huge differences in plant oil
 properties. For example, a fatty acid molecule with two bends may be sensitive
 to heat, while a fatty acid with an added hydroxy group is heat-resistant and
 performs wells as a high-temperature lubricant.

 While there are hundreds of applications for existing plant oils, even more
 uses could arise from novel oils produced by plants that are given new
 enzymes.

 The Brookhaven-Carnegie experiments were not performed on crop plants whose
 oils are harvested for industrial use, but if crop plants could be similarly
 changed, farmers could produce a far more diverse set of oils.

 Enzymes are made of chains of amino acids, strung together in a certain order
 to create a specific architecture that determines its unique chemical
 function.

 By careful detective work, Shanklin and Brookhaven's Ed Whittle, along with
 Carnegie colleagues Chris Somerville and Pierre Broun, were able to identify
 which amino acids in the sequence are responsible for a particular activity of
 the desaturase and hydroxylase enzymes. By modifying the genetic blueprint for
 the enzymes, they swapped several amino acids from one enzyme for their
 equivalents in another enzyme.

 Then, they examined the consequences by implanting the genes in a plant known
 as Arabidopsis, plant scientists' equivalent of animal geneticists'
 well-studied fruit fly. An analysis of the oil that accumulated in the
 modified plant's seeds showed that the "morphing" had been successful - the
 desaturase had become a hydroxylase and vice versa.

 The changes centered around the enzymes' 'active sites' - areas that grab
 fatty acids and catalyze the chemical changes. "Picture an enzyme as an
 industrial punch press and its active site as the die," said Shanklin. "What
 we have essentially done is learned how to change the die to make the punch
 press produce a different product."

 This achievement, Shanklin continued, means that enzymes are more "plastic,"
 or able to be changed, than scientists had recognized. "Not only can this
 knowledge be put to work in the field of designer oils, it also has
 implications for the concept of patenting enzymes."

 Shanklin and his colleagues have studied desaturase and other plant enzymes
 for several years. In 1997, a team from Brookhaven and Sweden's Karolinska
 Institute were the first to alter a desaturase so that it made fatty acids
 bend at a different point and created an oil with slightly different
 characteristics.

 The research was funded by DOE's Office of Science.

 The U.S. Department of Energy's Brookhaven National Laboratory creates and
 operates major facilities available to university, industrial and government
 personnel for basic and applied research in the physical, biomedical and
 environmental sciences, and in selected energy technologies. The Laboratory is
 operated by Brookhaven Science Associates, a not-for -profit research
 management company, under contract with the U.S. Department of Energy.