In enzymology, a mannose isomerase (EC 5.3.1.7) is an enzyme that catalyzes the chemical reaction In enzymology, a mannose isomerase (EC 5.3.1.7) is an enzyme that catalyzes the chemical reaction Hence, this enzyme has one substrate, D-mannose, and one product, D-fructose. 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-mannose aldose-ketose-isomerase. Other names in common use include D-mannose isomerase, and D-mannose ketol-isomerase. This enzyme participates in fructose and mannose metabolism.