Collaborative Research: Interfacing Students at Three Universities to Elucidate Enzymatic Transformations of Guanide Compounds that Impact Health and the Environment

With the support of the Chemistry of Life Processes (CLP) program in the Division of Chemistry, Drs. Martin St. Maurice from Marquette University, Lawrence Wackett from University of Minnesota-Twin Cities, and Betsy Martinez-Vaz from Hamline University are studying the enzymes and metabolic pathways that microbes use to degrade guanide and biguanide compounds that are commonly found in fertilizers, fuel propellants and pharmaceuticals. The most notable example is the biguanide drug metformin, which represents the fourth most prescribed pharmaceutical on the planet. Metformin is entering wastewater treatment plants at an alarming rate, with no clear sense of how it is being degraded by microorganisms. Using detailed studies of enzyme structure/function, chemical biology, comparative genomics and microbiology, this project aims to identify the metabolic pathway(s) and characterize the bacterial enzymes responsible for biodegrading metformin and related guanide and biguanide compounds. This project is expected to provide useful data to assist scientists and engineers in the development of better bioremediation practices in municipal water treatment plants where metformin is a major entering chemical. Further, this project integrates teaching, mentorship and training across three universities by incorporating the proposed research directly into graduate training, multi-institutional undergraduate courses, career mentorship and summer internships, significantly broadening the impact of the project.This project seeks to generate a comprehensive description of the metabolic pathways that are available naturally for the degradation of guanidinium compounds by microbial species and their relevant enzymes in wastewater and also in the human gut environment. The central metabolic artery includes the combined activities of guanylurea hydrolase, guanidine carboxylase, carboxyguanidine deiminase and allophanate hydrolase. The molecular contributions to the substrate selectivity of guanidine carboxylase will be characterized by x-ray crystallography and enzyme kinetic analysis. The structure and function of the carboxyguanidine deiminase enzyme will be examined by investigating the mechanism of catalysis, the functional role of the subunits and the potential for substrate channeling. The pathway and enzyme(s) responsible for bacterial metformin degradation will be identified by a combination of enzyme isolation, purification, and comparative genomics, across potentially relevant bacterial species, followed by detailed structural and functional characterization of the metformin-degrading enzyme(s). This project is expected to provide new information on how biguanide compounds are funneled into biodegradation pathways, providing a gateway to better understanding of how one important class of nitrogen-rich man-made compounds, produced across a variety of industrial sectors, is environmentally degraded.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.