The enzyme was identified as a highly homologous protein to aldose reductase. In enzymology, aldose reductase is a cytosolic NADPH-dependent oxidoreductase that catalyzes the reduction of a variety of aldehydes and carbonyls, including monosaccharides. It is primarily known for catalyzing the reduction of glucose to sorbitol, the first step in polyol pathway of glucose metabolism. The two enzymes differ in their pH optima and salt requirement, but they act on a similar spectrum of substrates.