Morphing Plant Enzymes for use in oil fabrication
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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
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
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'
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
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
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
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.