Resolution and Partial Characterization of Two Aldehyde Reductases of Mammalian Liver

Investigation of NADP-dependent aldehyde reductase activity in mouse liver led to the finding that two distinct reductases are separable by DE52 ion exchange chromatography. Aldehyde reductase I (AR I) appears in the effluent, while aldehyde reductase II (AR II) is eluted with a salt gradient. By several procedures AR II was purified over 1100-fold from liver supernatant fraction, but AR I could be pruified only 107-fold because of its instability. The two enzymes are different in regard to pH optimum, substrate specificity, response to inhibitors, and reactivity with antibody to AR II. While both enzymes utilize aromatic aldehydes well, only AR II ACTS ON D-glucuronate, indicating that it is the aldyhyde reductase recently reported to be identical to NADP-L-gulonate dehydrogenase. The presence of two NADP-linked aldehyde reductases in liver has apparently not heretofore been reported.