Design, synthesis and evaluation of inhibitors for tryptophan indole-lyase, tyrosine phenol-lyase and enzymatic synthesis of tryptophan from glycerol using tryptophan indole-lyase
Do, Quang Trong
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This dissertation is written in chapter format following the guidelines of the Graduate School of The University of Georgia. Chapter 1 will serve as an introduction to provide readers with relevant literature review. Chapters 2, 3 and 4 are copies of manuscripts prepared for submission to peer-reviewed journals. Chapter 5 provides a conclusion with emphasis on future research directions. Part of my research interest focuses on the design, synthesis and evaluation of mechanism-based inhibitors for tryptophan indole-lyase (TIL) as an approach to a novel class of antibacterial treatment (Chapter 2). Our results indicated that homologation of the physiological substrate, L-tryptophan, at the Cα position effectively inhibited the activity of TIL while displaying high selectivity in preference to tryptophan synthase. The accepted mechanism for TIL and tyrosine phenol-lyase (TPL) is remarkably similar. Therefore, we also extended our design and rationale in the search for potent mechanism-based inhibitors of TPL. Synthesis, inhibition kinetics and pre-steady-state kinetic evaluation of inhibitors for TPL is discussed in Chapter 3. TIL can also catalyze the reverse of its physiological reaction, β-substitution of indole, to yield L-tryptophan. As a proof-of-concept, we have demonstrated and validated the biosynthetic pathway for L-tryptophan from glycerol surplus by coupling natural glycerol metabolic enzymes of Escherichia coli with TIL expressed from tnaA plasmids (Chapter 4). This work presented an attractive and convenient alternative to the multi-step chemical synthesis for L-tryptophan, using a “one-pot” approach with whole-cell catalysis. The final chapter will provide a discussion on future research direction for the work reported in this dissertation.