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Our laboratory is interested in the mechanism of metalloproteins involved in radical generation and radical-catalyzed chemical conversions. All of the enzymes being investigated have significant roles in metabolic processes that are essential to human health and some of the enzymes have great potential as industrial catalysts. The research being done in this laboratory falls into two distinct research areas described below;

Heme degradation by enteric pathogens;

      All living organisms require iron in order to survive. Enteric pathogens have long since recognized that heme is the largest reservoir of iron in a mammalian host. Our laboratory is investigating the mechanism of heme acquisition, transport, and degradation in these pathogens.  Due to the anoxic environment that is often colonized by these pathogens our research is focused on the anaerobic mechanism of heme degradation. Our laboratory has identified a radical SAM methyltransferase (RSMT) and NADPH-dependent reductase that work together to catabolize heme in the enterohemorrhagic serotype of E. coli O157:H7. Deletion of the reductase results in a fitness phenotype and a 40% decrease in the infection rate of the pathogen. Therefore, understanding the mechanism of the anaerobic heme degradation pathway therefore represents an unexplored avenue for antibiotic development.

Enzymes as industrial catalysts;

      Numerous publications and patents have demonstrated the utility of using engineered organisms, engineered enzymes, or both, in the production of valuable commodity chemicals that are of great importance to maintaining our current standard of living. Traditionally these chemicals are obtained from natural resources and therefore these bioprocesses will become increasing more important as the energetic cost to extract reduced hydrocarbons from the earth increases. In order to expand the library of enzymatic conversions at the disposal of the metabolic pathway engineers, we are interested in characterizing the mechanism of enzymes that utilize radical chemistry to catalyze difficult chemical conversions. Of particular interest are a class of enzymes that utilizes a [4Fe-4S] cluster to catalyze the reductive cleavage of S-adenosylmethionine (SAM) and radical generation. These “radical SAM” enzymes are widespread in Nature and catalyze an astonishing array of complex and chemically challenging reactions. Similarly, the glycyl radical enzymes (GREs) catalyze a wide array of chemical rearrangements. Together, radical SAM enzymes and GREs catalyze C-C bond formation, C-C bond cleavage, dehydration reactions, C-N bond cleavage, C-S bond formation, methylthiolation reactions, and complex ring rearrangements. However, given the numerous GREs and radical SAM enzymes that have been identified within microbial and eukaryotic genomes, a considerable amount of functional diversity remains to be discovered, let alone engineered.

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