Fig. 5.

Proposed sequential reaction steps for FurX and other tetrameric ADHs. The possible hydrogen bonds are shown with a dashed line. All the steps except for the E1 step (boxed with dotted line) have been observed in the crystal structures. The corresponding step for E1 could not be observed due to the instability of FurX crystals in 100% furfuryl alcohol, thus was deduced from our observed binary complex structures of glycerol, isopropanol and furfural.