Challenging Limits: USU Biochemists Aid Grasp of Life-Critical Enzyme

Research by Utah State University professor Lance Seefeldt and his students is featured as a top June 2015 highlight on a U.S. Department of Energy website. In collaboration with the Pacific Northwest National Laboratory and several universities, Seefeldt’s team is zeroing in on a long-standing mystery of how bacterial enzymes known as nitrogenases convert nitrogen into life-sustaining compounds on which all plants and animals depend for survival.

The team’s discoveries, which could have significant implications for the world’s food supply and energy production, are reported in a recent issue of Biochemistry.

In addition to Seefeldt, the paper’s authors include USU doctoral students and recent graduates Karamatuallah Danyal, Andrew “A.J.” Rasmussen, Boyd Inglet, Sudipta Shaw and Simon Duval. Additional authors of the DOE and National Science Foundation-funded research include Stephen Keable, Oleg Zadvornyy and John Peters of Montana State University, Dennis Dean of Virginia Tech and Simone Raugei of PNNL.

“We live in a sea of nitrogen, yet our bodies can’t access it from the air,” says Seefeldt, professor in USU’s Department of Chemistry and Biochemistry. “Instead, we get this life-sustaining compound from protein in our food.”

It sounds simple, but converting enough nitrogen to supply the world’s food needs is complex and energy-intensive. Two known processes can break nitrogen’s ultra-strong bonds and allow conversion; global food demand currently depends equally on both. One is a natural, bacterial process. The other is the century-old, man-made Häber-Bosch process for fertilizer production, which currently consumes nearly two percent of the world’s fossil fuel supply.

“Using the Häber-Bosch method to synthesize ammonia for fertilizer from nitrogen requires massive amounts of hydrogen,” says Seefeldt, an American Association of the Advancement of Science Fellow. “Yet, in the natural process, nitrogenase produces ammonia without added hydrogen.”

In studying the enzyme, the USU team and its research partners noted how nitrogenase uses protons and elections, rather than added hydrogen, to catalyze a reaction. Through experimentation and computational analysis, the researchers deciphered chemical and mechanical steps of the natural fixation process.

“In essence, we were able to take some of the energy off the table and drive electrons toward the enzyme to produce ammonia,” Seefeldt says. “This was a very intricate process, requiring our students to engineer proteins by changing one or two individual atoms among some 10,000 atoms forming a molecule and figuring out, step by step, the consequences of changing those atoms.”

The team’s findings, he says, could contribute to a game-changing method of fertilizer and energy production. The researchers envision eventual use of solar energy to mobilize electrons into the enzyme, thus eliminating the need for highly polluting fossil fuels for fertilizer production.

“Our efforts were a success because of the interdisciplinary team we brought together to pursue this work,” Seefeldt says. “It was the ideal marriage of multiple areas of expertise.”

Related links: