John Shanklin, biochemist at Brookhaven National Laboratory, and Ed Whittle, research assistant in Shanklin's lab, with a fatty acid molecule model and plant seeds and casings in the foreground. | Courtesy of Brookhaven National Laboratory
A "bond" intertwined with international mystery and adventure? No, I'm not talking about Ian Fleming's dashing spy, James Bond, but rather a 40-year mystery involving bonds, double bonds. It’s a finding that could have billion-dollar implications that might leave the world of science stirred, if not shaken.
Recently, researchers in the Energy Department’s Brookhaven National Laboratory (BNL) figured out how an enzyme, a protein machine that specializes in driving high-speed chemical reactions, “knows” how to insert double bonds with pinpoint precision in plants' fatty acids. These fatty acids are used in a vast range of products, from polymers to plastics and soaps to industrial feed stocks -- making up an estimated $150 billion market annually. Understanding how proteins exert that precise control could show the way to the designer production of plant fatty acids, and, in turn, to new industrial applications and new products.
Plant fatty acids consist largely of long chains of indistinguishable carbon atoms, with hydrogen atoms stuck to their outside frame. Inserting a double bond – a process also known as desaturation – essentially means pulling a pair of hydrogen atoms from their carbons. An enzyme, known a desaturase, inserts double bonds at specific sites in the long carbon chain.
The BNL team of researchers, led by BNL's Dr. John Shanklin and with assistance from colleagues in Sweden's Karolinska Institute, first took a look at two different desaturases, which insert double bonds in different locations. However, the two enzymes looked virtually identical – nothing in their structures showed how they might work differently. So the scientists then used additional crystallography and computer modeling to determine how the two desaturases bind the fatty acids upon which they were working.
They discovered something extraordinary: a single amino acid, far from the enzyme’s active site, remotely controlled the site of the double bond placement.
“Using what we’ve now learned, I am optimistic we can redesign enzymes to achieve new desirable specificities to produce novel fatty acids in plants. These novel fatty acids would be a renewable resource to replace raw materials now derived from petroleum for making industrial products like plastics,” Shanklin said.
Read more about their work in the Proceedings of the National Academy of Sciences.
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