Structural and functional properties of enzymes involved in persulfide degradation

East Carolina University received a $525,000 Project Grant from the National Science Foundation's Division of Chemistry under the Mathematical and Physical Sciences program (CFDA 47.049), awarded September 1, 2025, with completion targeted for August 31, 2028. Under the direction of Professor Holly Ellis, the research team will investigate the structural and functional properties of enzymes involved in persulfide degradation, specifically examining a mercaptopropionate dioxygenase (MDO) and sulfurtransferase (ST) enzyme system. The primary deliverable is the elucidation of the catalytic mechanisms and structural features of the MDO/ST enzyme complex, which catalyzes the oxidation of low molecular weight thiols and persulfides in bacteria. This research addresses a significant knowledge gap regarding these ubiquitous bacterial enzymes through comprehensive biochemical and analytical characterization.

The project integrates substantive educational components alongside core research deliverables, with graduate students developing biochemical and analytical skills necessary for innovation in research and biotechnology, while high school students receive training in biochemical techniques through a pre-college program. Additionally, the award includes a federal grant sub-award to the University of Miami, where the Acevedo group will provide molecular dynamics simulations and computational analysis of the ST enzyme system. The sub-awardee will conduct molecular dynamics simulations under multiple experimental parameters to evaluate sulfur acceptor binding dynamics and will deliver all resulting data, analyses, and molecular structures in Protein Data Bank (PDB) format to the principal investigator.

Abstract

With support from the chemistry of life processes program in the division of chemistry, professor holly ellis and her research team at east carolina university will study the functional and structural attributes of a recently identified enzyme system that is metabolically relevant and involved in persulfide oxidation. The system consists of a mercaptopropionate dioxygenase (MDO) and a sulfurtransferase (ST), and IT is involved in a novel pathway in persulfide oxidation. Interestingly, the MDO/ST enzymes have been identified in a wide range of bacteria, suggesting that IT is critical to cellular function. Despite its ubiquity in bacteria, information about the mechanism of transformations catalyzed by the MDO/ST system is limited. The project focuses on filling this GAP through the elucidation of the functional and structural properties of the enzymes. Graduate students engaged in this research are learning the biochemical and analytical skills needed to drive innovation in research and biotechnology. The project is also integrated with a pre-college program to train high school students in different biochemical techniques used to understand enzyme function. Oxidation and assimilation of persulfides in bacteria is often catalyzed by enzymes critical in maintaining potentially toxic persulfide levels and in supplying bacteria with alternative sulfur sources. The MDO thiol dioxygenases that catalyze the oxidation of low molecular weight (LMW) thiols were originally identified due to their structural similarity to mammalian enzymes. However, the expression of an ST enzyme on the same operon as MDO suggests that the full catalytic function of these enzymes has not been identified. The project will evaluate the functional and structural features of the MDO/ST enzymes that promote catalysis. Objective 1 is the study of the catalytic mechanism of the MDO/ST enzymes. A comprehensive approach will be used to gather information about a common mechanism for persulfide oxidation by the MDO/ST enzymes. Objective 2 is to identify the structural features of most MDO/ST enzymes that promote catalysis. Complementary spectroscopic and biophysical approaches will be utilized to identify structural dynamics that contribute to catalysis. 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.- subawards are planned for this award.