Oxidation of 21-Dehydrocorticosteroids to Steroidal 20-Oxo-21-oic Acids by an Aldehyde Dehydrogenase of Sheep Adrenal

Sheep adrenal cortex contains an enzyme which catalyzes the oxidation of steroidal 20-oxo-21-al derivatives to 20-oxo-21-oic acids. The enzyme was purified 60- to 70-fold and retained broad specificity for a variety of aliphatic and aromatic aldehydes. The aldehyde dehydrogenase was localized in the cytosol. It was protected from inactivation by NAD+, which it uses as specific coenzyme, but was otherwise unstable. Reagents that react with —SH groups inactivated the enzyme. Molecular weight was estimated as 164,000. The product of 21-dehydrocorticosterone oxidation was 11β-hydroxy-3,20-diketo-4-pregnen-21-oic acid. For each mole of product made or substrate used, 1 mole of NAD+ was reduced.