Most commonly known as “the fruit-ripening hormone,” the gaseous hydrocarbon ethylene (C2H4) is produced in nature by plants and microbes. Of the four known biochemical pathways to ethylene, two rely on mononuclear nonheme iron enzymes to generate the simplest alkene by oxidative fragmentations of their substrates. Whereas the plant enzyme, 1-aminocyclopropane-1-carboxlic acid oxidase (ACCO), requires a specialized substrate and produces toxic hydrogen cyanide concomitantly with ethylene, microbial ethylene-forming enzyme (EFE) transforms a ubiquitous and abundant primarily metabolite, 2-oxoglutarate (2OG), and produces only CO2 as a co-product, potentially making it a more suitable platform to support a renewable bioprocess to ethylene. In this presentation, I will describe how my team has used kinetic, spectroscopic, and biochemical methods, along with structural biology, to uncover the mechanism by which EFE produces ethylene. I will also discuss how the insights gleaned from these investigations might i) inform efforts to utilize EFE for renewable production of ethylene and other commodity chemicals and ii) encourage re-examination of mechanisms of O2 activation by other iron(II)- and 2OG-dependent oxygenases.

Mechanism of conversion of the TCA cycle intermediate 2-oxoglutarate into ethylene by the microbial ethylene-forming enzyme

ACS Fall 2021

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