Through the biological fixation of the element nitrogen by the enzyme nitrogenase, organisms gain access to molecular nitrogen (N2) in the Earth’s atmosphere, which is essential for building cellular structures. In addition, a vanadium-dependent variant of nitrogenase can reduce the toxic gas carbon monoxide (CO) to hydrocarbons. These reductions of N2 and CO are among the most important processes in industrial chemistry, as they are used to produce both fertilizers and synthetic fuels. However, researchers have not yet been able to decipher the different pathways of the two reactions.