Chris Somerville, director of the Carnegie Institution's Department of Plant Biology, Pierre Broun, a former postdoctoral fellow at the department, and John Sahanklin and Ed White of the Brookhaven National Laboratory report in the November 13 issue of Science on their experimental successes with directed interconversions of enymes that modify plant fatty acids. Their results represent a step toward the production of novel plant fatty acids by genetic manipulations.
In their experiments, Somerville, Broun, and colleagues uncovered a surprising "plasticity" in enzymes, a property that one day might lead to creation of enzymes that have not been found in nature. The work has important implications for the development of useful new chemicals from plants, such as the production of novel diacids for use in high-temperature lubricants or as feedstocks for polyamide synthesis.
The Carnegie/Brookhaven team reported the directed conversion of a fatty acid desaturase into a fatty acid hydroxylase. The research group was also successful in doing the converse: converting a hydroxyase into a desaturase by making as few as six amino acid changes. In addition, Somerville and colleagues proposed that amino acid variations in the same enzyme can cause the formation of triple bonds and epoxy groups. Thus, this discovery reveals the chemical mechanisms responsible for the formation of most of the chemical diversity found in plant fatty acids. "Basically," says Somerville, "the underlying chemical reaction is very promiscuous and the enzymes have harnessed this 'catalytic promiscuity' to create a huge amount of diversity." The discovery raises the possibility that it may be possible to create a family of novel synthetic enzymes that produce industrially useful fatty acids with a wide range of chemical structures.
Carnegie Institution. November 1998.