Guanidine is a potential nitrogen fertilizer and ethylene has been proposed as a potential alternative fuel source; thus, the biosynthetic reactions that form these compounds are commercially important as they have potential benefits for agriculture and the biofuels industries. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Drs. Robert Hausinger and Jian Hu at Michigan State University, and Dr. Christo Christov at Michigan Technological Institute to investigate how ethylene-forming enzyme (EFE) from bacteria and fungi catalyzes dual reactions to form guanidine or ethylene. In the typical reaction of EFE, a carbon dioxide is removed from other molecules (2-oxoglutarate, or 2OG), while being added to the amino acid, L-arginine, to transform it into guanidine. Alternatively, EFE catalyzes the transformation of 2OG into ethylene, with the release of carbon dioxide / bicarbonate. Research into the mechanisms of EFE catalysis provides specialized biochemical, structural, and computational training to postdoctoral fellows, and graduate and undergraduate students, including women and students from underrepresented minority groups. Incorporation of these studies into a university science festival engages families and lifelong learners through outreach programs about the potential use of ethylene as a biofuel.
The overarching goals of this research project are to elucidate the molecular determinants that distinguish the two distinct reactions catalyzed by EFE and to establish the catalytic mechanisms of the enzyme by a combination of experimental and computational studies. This work also investigates why other members of the iron(II)- and 2OG-dependent oxygenases fail to produce ethylene. To understand the basis of the two EFE-catalyzed reactions, the researchers are characterizing naturally occurring analogs, a reconstructed ancestor, and site-directed variants of the protein by using kinetic, structural, and computational methods. Using this information along with structure-guided protein engineering, the researchers are creating EFE variants optimized for the production of either the biofuel ethylene or the plant fertilizer guanidine while eliminating wasteful L-Arginine hydroxylation or 2OG-degrading reactions. In addition, the team is using biochemical, kinetic, spectroscopic, and computational methods to elucidate the chemical reaction mechanism of EFE. This work extends the structural/mechanistic information available on other important iron(II)- and 2OG-dependent oxygenases that are unable to catalyze these reactions.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
