In enzymology, a D-lyxose ketol-isomerase () is an enzyme that catalyzes the chemical reaction
Hence, this enzyme has one substrate, D-lyxose, and one product, D-xylulose.
This enzyme belongs to the family of isomerases, specifically those intramolecular oxidoreductases interconverting aldoses and ketoses. The systematic name of this enzyme class is D-lyxose aldose-ketose-isomerase. Other names in common use include D-lyxose isomerase, and D-lyxose ketol-isomerase. This enzyme participates in pentose and glucuronate interconversions.
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and .