UPTON, NY -- If your experiment doesn't go the way you expect, take a closer look -- something even more interesting may have happened. That strategy has led scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory to discover a fundamental shift in an enzyme's function that could help expand the toolbox for engineering biofuels and other plant-based oil products. The results will be published online the week of September 8, 2008, in the Proceedings of the National Academy of Sciences.
The Brookhaven scientists were trying to understand the factors that affect where carbon-carbon double bonds are placed in fatty acids, the building blocks of oils and fats, when they are "desaturated" -- that is, when a desaturase enzyme removes hydrogen from the carbon chain.
"Placing double bonds in different positions allows you to change the structure of the fatty acids to make products with different potential applications," explained Brookhaven biochemist John Shanklin, who led the research. The ultimate goal: engineering designer plant oils to be used as biofuels and/or raw materials to reduce the use of petroleum.
To try to change the position of a double bond, the Brookhaven team modified a desaturase enzyme, changing three of the 363 amino acids in its protein sequence. But when they tested the modified enzyme and looked for the expected product with its altered double-bond position, it wasn't there.
They could have moved on and made different amino acid changes to accomplish the initial goal. But Brookhaven research associate Edward Whittle was determined to figure out what was going on with the unusual result. "The substrate, or starting material, had been used up, so something was being produced -- substrates can't just disappear," Whittle said. "If it wasn't the product we were looking for, what was it?"
Whittle's detective work uncovered a remarkable discovery. Instead of producing a
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DOE/Brookhaven National Laboratory