Crystal structures of <i>Klebsiella oxytoca</i> ribitol dehydrogenase in complex with <scp>NAD</scp> ⁺ , <scp>d</scp> ‐allose, or <scp>d</scp> ‐allulose reveal insight into substrate recognition

, d-allulose, or d-allose. Although d-allose is an aldose and not a substrate of KoRdh, it binds to KoRdh in the pyranose form, revealing the location of the substrate-binding site. Based on these structures, we propose a substrate recognition mechanism for KoRdh. Impact statement This research reveals an insight into a substrate recognition mechanism in the flexible region of ribitol dehydrogenase. Because ribitol dehydrogenase is a member of the short-chain reductases/oxidases (SDR) family, the current study will provide further insight into related enzymes that harbor the flexible region.