Isobutanol, can be synthesized in a cell free cascade using five enzymes and starting from pyruvate as the initial substrate. Three of the enzymes in this pathway are catalytically efficient, but the second enzyme, ketol-acid reductoisomerase (KARI), has a relatively low turnover number and generally requires NADPH (an expensive cofactor) for activity. Here, we are exploring the properties of a KARI isolated from Campylobacter jejuni (Cj KARI) to determine if it could be a useful enzyme for inclusion into the cascade. To date, we have determined that the protein is dodecameric and, unusually, it can use either NADPH or NADH as a cofactor, NADH with an efficiency 10-fold lower than for NADPH. This enzyme is stable at temperatures as high as 55°C, a property than makes it suited for industrial applications. To further characterize the protein, small angle X-ray scattering (SAXs) has been performed, which confirms in solution that the protein is dodecameric. An initial Cryo-EM 3D model of the structure has been determined, this at 7 Å resolution. The structural data will provide useful information relevant to this enzyme’s substrate and cofactor specificity, explain why Mg2+ is the only metal ion that it can use, and also explain its preference for NADPH as a cofactor. Furthermore, it will be useful as a starting point for rational molecular design approaches aimed at making versions of this enzyme that could be highly suited for industrial applications.