Activation of Methyl-substituted Benzenes in Anaerobic Bacteria

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Microbial enzymes, specifically those of anaerobic microbes, are receiving significant attention because they provide an invaluable source for diverse natural catalysts. Of particular interest are those enzymes that catalyze the transformation of relatively unreactive organic compounds. Methyl-substituted benzenes, such as toluene, xylenes, and trimethylbenzenes, are relatively stable and represent important drinking water contaminants that are released into the environment from leaking underground gasoline storage tanks and surface spills. Several diverse, anaerobic, toluene--mineralizing microbes have been isolated and studied in more detail to gain insight into the mechanism of anaerobic activation of toluene. These studies showed that the initial reaction of anaerobic toluene metabolism is the addition of the toluene methyl group to fumarate to form benzylsuccinate. Benzylsuccinate synthase (BSS), which catalyzes this reaction, is emerging as a prototype of a new class of enzymes for activation of methylbenzenes. Recent studies strongly suggest that BSS is a radical enzyme, which carries an essential glycyl radical. Using spectroscopic as well as biochemical and genetic studies, this project will investigate the involvement of a radical in the BSS reaction and examine the mode of BSS activation.This project will further our understanding of the pathways used by microbes to degrade highly stable organic compounds that represent important contaminants of drinking water. This information should help in developing effective biological means of removing these contaminants from water.