1ZEM: Crystal Structure of Nad+-bound Xylitol Dehydrogenase

Xylitol dehydrogenase (XDH) is one of several enzymes responsible for assimilating xylose into eukaryotic metabolism and is useful for fermentation of xylose contained in agricultural byproducts to produce ethanol. For efficient xylose utilization at high flux rates, cosubstrates should be recycled between the NAD+-specific XDH and the NADPH-preferring xylose reductase, another enzyme in the pathway. To understand and alter the cosubstrate specificity of XDH, we determined the crystal structure of the Gluconobacter oxydans holoenzyme to 1.9 angstroms resolution. The structure reveals that NAD+ specificity is largely conferred by Asp38, which interacts with the hydroxyls of the adenosine ribose. Met39 stacked under the purine ring and was also located near the 2' hydroxyl. Based on the location of these residues and on sequence alignments with related enzymes of various cosubstrate specificities, we constructed a double mutant (D38S/M39R) that was able to exclusively use NADP+, with no loss of activity.
PDB ID: 1ZEMDownload
MMDB ID: 37936
PDB Deposition Date: 2005/4/19
Updated in MMDB: 2007/10 
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 1ZEM: tetrameric; determined by author and by software (PISA)
Molecular Components in 1ZEM
Label Count Molecule
Proteins (4 molecules)
Xylitol Dehydrogenase
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB