Harmful Turned Harmless

December 05, 2017

Mikael Elias and colleagues engineer an enzyme that rapidly neutralizes the toxicity of common pesticides and herbicides.

Mikael Elias in his lab

Mikael Elias in his lab in St. Paul.

“Our enzymes are the first that can break down a wide range of these compounds in minutes and render them non-toxic." 

Wash fruits and vegetables before eating them. Everyone knows that! But the traces of herbicide residue on the surface of most conventional produce and even some organic produce isn’t so easy to remove, as it turns out. “Unfortunately, organophosphorous compounds are very hydrophobic,” says researcher Mikael Elias, which means using water won’t work. You could try immersing your fresh produce in bleach instead, but the end result would be unappetizing to say the least.  

Developed in the late 1930s for use in agriculture and, later, in biological weapons, organophosphorous compounds, or OPs, are widely used all over the world. While they are very effective at keeping bugs at bay and thereby increasing yields for farmers that, in turn, feed a growing population, they are also associated with cancers and neurological disorders such as autism and lower IQ, and, on a darker note, with terrorist attacks.

Looking for a way to mitigate the effects of these common compounds, Elias and colleagues decided to investigate the potential of engineered enzymes to get the job done. They reported their findings in recent papers. One looks at differences in catalytic activity between two enzymes that can degrade OPs. The other describes an enzyme engineered by Elias that could prove a game changer. “Our enzymes are the first that can break down a wide range of these compounds in minutes and render them non-toxic,” says Elias.

Organophosphorous compounds irreversibly inhibit a key enzyme of the central nervous system, essentially scrambling messages and disrupting basic functions. This makes the compounds highly effective as a weapon against insects, but also birds and other animals. As it turns out, humans are a little less vulnerable due to the presence of an enzyme in mammalian blood. Researchers isolated and named the enzyme PON1 (serum paraoxonase 1) and it has been the subject of much study by scientists looking for clues to combating the toxicity of organophosphorous compounds.

But PON1 enzymes have some limitations. For one thing, they are difficult to engineer due to their hydrophobic character and lack of stability, which makes it difficult for researchers to achieve desired outcomes consistently. Plus, enzymes have preferences. In the case of PON1 that means an inclination to latch on to less toxic compounds more often than not, making it less effective overall.

By contrast, Elias characterizes his enzyme as extremely stable and “friendly,” noting that it is decidedly less finicky than PON1, readily going to work on a broad range of OPs. Its stability is a key property, which enables numerous possible applications in the area of biodecontamination. “We’re working on some ideas for incorporating the enzyme in the food production process and in consumer goods. There is great potential in using these 100 percent biodegradable tools to make our food safer.”  – Stephanie Xenos