Ethylene is a prolifically manufactured chemical feedstock derived primarily from petroleum. Ethylene is also found in nature, where it is a key regulator of plant development and is produced by plants and some plant-associated microbes. In one such microbial pathway, the iron-dependent oxygenase, ethylene-forming enzyme (EFE), globally fragments the ubiquitous primary metabolite, 2-oxoglutarate (2OG), to form ethylene (from carbons 3 and 4) and three carbon-dioxide equivalents (from carbons 1, 2, and 5). Other members of the large family of enzymes to which EFE belongs (the Fe/2OG oxygenases) cleave only the C1-C2 bond of 2OG to drive reductive cleavage of O2 and formation of hydrogen-abstracting oxoiron(IV) (ferryl) intermediates. EFE is capable of this standard reactivity in its minor reaction, in which it fragments L-arginine after abstracting hydrogen from C5. This presentation will summarize our evidence that EFE generates a ferryl intermediate only in its minor pathway and instead uses a unique radical-polar mechanism that diverges from the ferryl-forming pathway before O2 cleavage in order to accomplish its major, ethylene-yielding reaction. Understanding this mechanism promises to allow EFE to be used in bioprocesses for several important polymer feedstocks.

Award Address (Nobel Laureate Signature Award for Graduate Education in Chemistry sponsored by Avantor). Production of ethylene and other commodity chemicals by the iron- and 2-(oxo)glutarate-dependent ethylene-forming enzyme

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