Abstract for parent grant: Enzymes are powerful biocatalysts that may be repurposed for efficient and sustainable synthesis of industrial and pharmaceutical compounds. Identifying novel enzyme-catalyzed reactions and understanding their catalytic mechanisms is essential for expanding the biocatalytic toolbox. We have recently discovered a unique copper-containing antibiotic, fluopsin C, which is produced by Pseudomonas aeruginosa, a leading cause of multidrug-resistant nosocomial infections. By studying how P. aeruginosa makes fluopsin C, we identified an unusual biosynthetic pathway that involves novel enzyme chemistry. For instance, two iron- dependent enzymes of a new heme-oxygenase-like enzyme family catalyze a carbon excision and an oxidative decarboxylation and N-hydroxylation respectively. Two lyases of the adenylosuccinate lyase enzyme family exhibit novel activities of making and breaking carbon- sulfur bonds respectively. The chemistries we identified have expanded the catalytic capabilities of these enzyme families. We hypothesize that the fluopsin C biosynthetic enzymes use novel catalytic mechanisms and can be repurposed or engineered to generate new molecules. To test this hypothesis, we will use a combination of enzyme kinetics, structural biology, spectroscopy, and synthetic chemistry tools, with a focus on three enzymes in fluopsin C biosynthesis. Studies of these distinct enzymes will advance the fundamental understanding of how their respective enzyme family catalyzes diverse chemistry. Defining the mechanisms and substrate scope of the enzymes will allow them to be further explored for biocatalytic use.