Structural and Functional Properties of Enzymes Involved in Persulfide Degradation

East Carolina University, Greenville NC

Investigators

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.