URBANA, Ill. — Nature is a remarkably good chemist. Inside every living cell, enzymes speed up chemical reactions, building, breaking apart, and rearranging molecules with a precision that human chemists have long tried to replicate.
But nature’s chemical toolbox has limits.
Researchers at the University of Illinois Urbana-Champaign have engineered an enzyme to perform a reaction that almost never happens in nature. They demonstrated the new ability by using it to make L-glufosinate, the active ingredient of a widely used agricultural herbicide.
The findings, published in Science, could expand the range of useful chemicals that scientists can make using enzymes, including compounds used in agriculture and medicine.
The work was supported by the U.S. Department of Energy Center for Advanced Bioenergy and Bioproducts Innovation, or CABBI, based at Illinois.
“Nature has evolved enzymes to carry out an enormous number of chemical reactions, but it doesn’t necessarily give us the enzymes we need to make the products we want,” said Huimin Zhao, the study’s corresponding author and CABBI Conversion Theme Lead. “Our work shows that we can engineer an existing enzyme to perform new chemistry and use that chemistry to make a commercially important product.”
Engineering a new enzyme function
Enzymes are attractive tools for manufacturing because they can perform chemical reactions with high precision under relatively mild conditions. But scientists are limited by the reactions enzymes can perform naturally.
One particularly difficult task is forming bonds between carbon and phosphorus. These bonds are found in many useful products, from medicines to agricultural chemicals, but enzymes capable of creating them are extremely rare in nature. Chemists can make carbon-phosphorus bonds through other methods, but those approaches can require harsh chemicals and multiple carefully controlled steps, making it complex and resource-intensive.
Zhao, a professor of chemical and biomolecular engineering and a faculty member at the Carl R. Woese Institute for Genomic Biology, and his colleagues integrated enzyme catalysis with photocatalysis and used directed evolution — making variations of an enzyme and selecting those that perform better — to give an existing enzyme a new function.
The researchers tested more than 100 variations and combined the most promising changes. They then used machine learning to identify additional modifications that could improve the enzyme’s performance. Eventually, they produced an enzyme that could use oxygen to help join carbon and phosphorus.
The team put the new capability to the test by using it to make L-glufosinate, the active ingredient of a widely used broad-spectrum herbicide. Producing this form efficiently has long presented a chemistry challenge.
The engineered enzyme successfully produced L-glufosinate with very high precision, demonstrating that the new approach could be used to make an agriculturally important chemical.
The enzyme’s usefulness was not limited to glufosinate. In tests with a variety of materials, the researchers successfully produced a range of phosphorus-containing compounds, many with similarly high precision.
The results show that the approach could extend beyond a single product, giving researchers a new way to make phosphorus-containing compounds used in agriculture, medicine, and other applications.
“Our repurposed enzymes represent a new-to-nature class of enzymes and potentially have many applications,” said Zhao. “We will further optimize and scale up the synthesis process of L-glufosinate and extend the same enzyme engineering strategy to other types of chemical reactions of both scientific significance and practical importance.”
The study’s authors are Yi Zhou, Yifei Ge, Wesley Harrison, and Zhao, all of the University of Illinois Urbana-Champaign.
The research was funded by CABBI through the U.S. Department of Energy’s Office of Science, Biological and Environmental Research program under award No. DE-SC0018420. The work also used the Delta supercomputer at the National Center for Supercomputing Applications at Illinois through the National Science Foundation-supported Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support program.