In enzymology, a D-lyxose ketol-isomerase (EC 5.3.1.15) is an enzyme that catalyzes the chemical reaction

D-lyxose ${\displaystyle \rightleftharpoons }$ D-xylulose

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 1QO2 and 1VZW.

• ANDERSON RL, ALLISON DP (1965). "Purification and Characterization of D-Lyxose Isomerase". J. Biol. Chem. 240 (6): 2367–72. doi:10.1016/S0021-9258(18)97332-1. PMID 14304839.