Thesis advisor: Steven D. Bruner / Bacteria utilize complex enzymatic machinery to create diverse secondary metabolites. The architectural complexities of these small molecules are enhanced by nature’s ability to synthesize non-proteinogenic amino acids for incorporation into these scaffolds. Many of these natural products are utilized as therapeutic agents, and it would be advantageous to understand how the bacteria create various non-natural amino acid building blocks. With a greater understanding of these systems, engineering could be used to create libraries of potentially useful natural product analogs. The tyrosine aminomutase SgTAM from the soil bacteria Streptomyces globisporus catalyzes the formation of tyrosine to generate (S)-B-tyrosine. The precise mechanistic role of MIO in this novel family of aminomutases has not been established. We report the first X-ray crystal--> structure of an MIO based aminomutase and confirm the structural homology of SgTAM to ammonia lyases. Further work with mechanistic inhibitors provide structural evidence of the mechanism by which MIO dependent enzymes operate. We have also investigated LnmQ, an adenylation domain in the biosynthetic pathway of leinamycin. Leinamycin is an antitumor antibiotic that was isolated from soil samples in 1989. LnmQ is responsible for the specific recognition of D-alanine and subsequent activation as an aminoacyl adenylate species. We have cloned the gene into a DNA vector and expressed it in E. coli. Upon purification of the protein, crystallization conditions have been tested. Synthesis of an inhibitor that mimics the aminoacyl adenylate product catalyzed by LnmQ has been completed. Crystallization with this--> inhibitor will provide better quality crystals and a catalytically informative co-complex. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.