PURIFICATION AND PARTIAL CHARACTERIZATION OF A RAT-KIDNEY ALDEHYDE DEHYDROGENASE THAT OXIDIZES RETINAL TO RETINOIC ACID

A NAD-dependent aldehyde dehydrogenase (EC 1.2.1.3) which catalyzes th e oxidation of retinal to retinoic acid was purified to homogeneity fr om rat kidney by using Affi-Gel blue affinity chromatography and chrom atofocusing, followed by Mono-Q anion-exchange chromatography. The app arent molecular weight of the native enzyme determined by size-exclusi on fast protein liquid chromatography was 140 000. Sodium dodecyl sulf ate - polyacrylamide gel electrophoresis gave a subunit molecular weig ht of 53 000. The isoelectric point as measured by chromatofocusing wa s 8.5. The enzyme also catalyzed the oxidation of acetaldehyde, but sh owed much lower K(m) value for the retinal substrate. We suggest that aldehyde dehydrogenase found in the kidney may be a specific retinal d ehydrogenase, involved in vitamin A metabolism.