( CHAPEL HILL ?An enzyme inside a bacteri...)New discovery: If it weren't for this enzyme, decomposing pesticide would take millennia

That may be expensive for farmers but lucky for the environment because University of North Carolina at Chapel Hill scientists have now discovered that if that particular enzyme weren't there, it would take 10,000 years for just half of the widely used pesticide to decompose. And the chemical would remain in the soil of the potato fields where it is now used in colossal amounts, contaminating groundwater and posing a threat to human and animal health.

A report on the unusual discovery appears online in the Proceedings of the National Academy of Sciences Monday (Oct. 24). Authors are Christopher M. Horvat, a UNC chemistry major from Spruce Pine, who plans to become a physician, and Dr. Richard V. Wolfenden, Alumni Distinguished professor of biochemistry and biophysics at the UNC School of Medicine.

"The half-life of the pesticide is longer, by several orders of magnitude, than the half-lives of other known environmental pollutants in water," Wolfenden said. "The half lives of atrazine, aziridine, paraoxon and 1, 2-dichloroethane, for example, are five months, 52 hours, 13 months and 72 years, respectively."

In contrast, the half-life of the potato pesticide residue chloroacrylate -- 10,000 years -- matches the half-life of plutonium-239, the hazardous isotope produced in nuclear power plants, he said.

The bacteria Pseudomonas pavonaceae have evolved in the soil in which the potato pesticide 1, 3-dichloropropene is used and can grow on it as their only source of carbon and energy, the scientist said. The enzyme responsible for degrading the pesticide may have evolved since the chemical's first use on potato fields in 1946. Common names for the agricultural product are Shell D-D and Telone II.

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Source:University of North Carolina at Chapel Hill