Crystal structure of L-2-keto-3-deoxyfuconate 4-dehydrogenase reveals a unique binding mode as a α-furanosyl hemiketal of substrates.

L-2-Keto-3-deoxyfuconate 4-dehydrogenase (L-KDFDH) catalyzes the NAD-dependent oxidization of L-2-keto-3-deoxyfuconate (L-KDF) to L-2,4-diketo-3-deoxyfuconate (L-2,4-DKDF) in the non-phosphorylating L-fucose pathway from bacteria, and its substrate was previously considered to be the acyclic α-keto form of L-KDF. On the other hand, BDH2, a mammalian homolog with L-KDFDH, functions as a dehydrogenase for cis-4-hydroxy-L-proline (C4LHyp) with the cyclic structure. We found that L-KDFDH and BDH2 utilize C4LHyp and L-KDF, respectively.