The enzyme, characterized in the bacterium Rhodobacter sphaeroides, has a wide subtrate specificity. In addition to galactitol, it primarily oxidizes D-threitol and xylitol, and in addition to L-tagatose, it primarily reduces L-erythrulose, D-ribulose and L-glyceraldehyde. It is specific for NAD+. The enzyme also shows activity with D-tagatose (cf. EC 1.1.1.16, galactitol 2-dehydrogenase).
Enzyme evolution in Rhodobacter sphaeroides: selection of a mutant expressing a new galactitol dehydrogenase and biochemical characterization of the enzyme.