Wei Li

Graduation Semester and Year




Document Type


Degree Name

Doctor of Philosophy in Chemistry


Chemistry and Biochemistry

First Advisor

Brad Pierce


Cysteine dioxygenase (CDO) is an non-heme mononuclear iron enzymes that catalyzes the O2-dependent oxidation of L-cysteine (Cys) to produce cysteine sulfinic acid (CSA). CDO controls cysteine levels in cells and is a potential drug target for some diseases such as Parkinson's and Alzhermer's. Several crystal structures of CDO have been determined and they reveal a ferrous iron active site coordinated by three histidine residues. This feature is divergent from the monoanionic 2-histidine-1-carboxylate coordination typically observed within the non-heme mononuclear iron super family of oxidase/oxygenase enzymes. Furthermore, within 3.3 Å of the CDO active site iron is an unusual covalently crosslinked cysteine-tyrosine pair (C93-Y157). To date, only 3 other enzymes have been identified with a similar Cys-Tyr post-transitional modification and the role of this modification in CDO is still unknown. Due to the lack of structural evidence of oxygen-bound intermediates, the mechanism of CDO remains unclear. In this work, a transient intermediate FeIII-superoxo was discovered by chemical rescue reaction and characterized using UV-vis, EPR and resonance Mossbauer. To probe the influence of second-sphere enzyme-substrate interaction, the steady-state kinetics and O2/CSA coupling were measured for wild-type CDO and selected active site variants (Y157F, C93A, H155A). In additional, using CN- as a probe, the influence of the C93-T157 pair to the active site is investigated on EPR. Key substrate-enzyme interaction was also investigated by substrate specificity of CDO. Selected thiol-containing compounds were incubated with CDO for steady-state kinetic analysis using NMR. LC-MS confirmed the presence of products and dioxygenase activity.


Chemistry | Physical Sciences and Mathematics


Degree granted by The University of Texas at Arlington

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