Researchers led by Tokyo University of Science identified a groundbreaking enzyme that promises to revolutionize plant disease management. The discovery could lead to the creation of non-sterilizing anti-bacterial pesticides, curbing the devastation caused by Xanthomonas pathogens on crucial crops like rice, wheat and tomatoes.
In a major breakthrough for agriculture, a team of researchers led by Tokyo University of Science has identified an enzyme that could revolutionize the way plant diseases are managed. The enzyme, named XccOpgD, could lead to the development of new anti-bacterial pesticides that specifically target the pathogens causing widespread devastation without promoting drug resistance.
The findings, published in the Journal of the American Chemical Society, come from a study led by Masahiro Nakajima, an associate professor at Tokyo University of Science. The research team includes Sei Motouchi, a doctoral candidate from Tokyo University of Science, Hiroyuki Nakai, an associate professor at Niigata University, and Shiro Komba, a principal researcher from the Institute of Food Research at NARO National Agriculture and Food Research Organization).
Plant diseases, particularly those caused by the notorious Xanthomonas species, present severe challenges to agricultural productivity. These pathogens affect essential crops, such as rice, wheat and tomatoes, significantly reducing yields and causing substantial economic losses globally.
Previous research indicated that Xanthomonas pathogens utilize a cyclic compound, α-1,6-cyclized β-1,2-glucohexadecaose (CβG16α), to suppress plant defense mechanisms. The research team has now identified a glycoside hydrolase enzyme, XccOpgD, in the X. campestris pv campestris strain responsible for biosynthesizing CβG16α.
“Glycan structures are intricate and multifaceted and fulfill diverse crucial roles in nature and organisms. Enzymes synthesize and degrade glycans, exhibiting diverse structures and functions that correspond to the glycan diversity. However, our understanding of these enzymes is still limited, which drives the search for new enzymes with varied new potentials,” Nakajima said in a news release.
Utilizing advanced biochemical analysis and X-ray crystallography, the team elucidated the catalytic mechanism and substrate specificity of XccOpgD, revealing it as part of the GH186 enzyme family. This family is key in regulating bacterial cell wall components. Notably, XccOpgD operates through an unprecedented enzymatic mechanism called anomer-inverting transglycosylation.
“Reactions of typical GH enzymes are classified into four types by combination of retaining or inverting, and reaction with water (hydrolysis) or sugar (transglycosylation) theoretically. However, one classification is missing somehow in a long history of researches on carbohydrate associated enzymes and we discovered the missing classification,” added Nakajima. “This breakthrough was made possible by unique structural environment, opening new possibilities for enzyme-based glycosylation.”
The cyclic compound CβG16α was identified using nuclear magnetic resonance, and crucial substrate binding residues were pinpointed through structural analysis of the Michaelis complex. XccOpgD facilitates an anomer-inverting transglycosylation mechanism, with key catalytic roles played by residues D379 and D291.
This discovery holds immense potential for developing targeted anti-bacterial pesticides.
“We are expecting a pesticide concept targeting this enzyme homolog in the future. Unlike fungicides that promote the emergence of drug-resistant bacteria in soil, targeting this enzyme could potentially inhibit pathogenicity without causing sterilization,” Nakajima added. “Enzyme homologs identified in this study may serve as promising structure-based drug targets, offering a potential solution to the issue of drug-resistant bacteria.”
The breakthrough promises enhanced agricultural resilience, improved food security and mitigated environmental impacts linked to conventional pesticides. As researchers continue to explore the potential applications of XccOpgD, this advancement could pave the way for sustainable solutions to global agricultural challenges, benefiting farmers and ecosystems worldwide.