Guinea Pig Liver Aromatic Aldehyde-Ketone Reductases Identical with 17β-Hydroxysteroid Dehydrogenase Isozymes

Publisher Website
Google Scholar
Abstract
Two NADPH-dependent aromatic aldehyde-ketone reductases purified from guinea pig liver catalyzed oxidoreduction of 17β-hydroxysteroids and 17-ketosteroids. One enzyme efficiently oxidized 5β-androstancs and reduced 17-ketosteroids of A/B cis configuration, whereas the other enzyme efficiently oxidized 5α-androstanes and equally reduced both 5α-and 5β-androstanes of 17-ketosteroids. However, aromatic aldehydes and ketones, and 3-ketosteroids were irreversibly reduced by the two enzymes. The two enzymes utilized NADP+ or NADPH as cofactor, but little activity with NAD+ or NADH was found. Phosphate ions enhanced the NAD+-dependent dehydrogenase activity and NADH-dependent reductase activity of the two enzymes, whereas the activities with NADP+ and NADPH were not affected. The ratios of the two activities of ketone reduction and 17β-hydroxysteroid oxidation of the two enzymes were almost constant during the purification steps after the two enzymes had been separated by DEAE-cellulose chromatography. By kinetic studies and electrophoresis and isoelectric focusing experiments it was confirmed that both of the two enzymes were responsible for the reduction of aldehydes, ketones, and ketosteroids and for the oxidation of 17β-hydroxysteroids. These results indicate that 17β-hydroxysteroid dehydrogenases may play important roles in the metabolism of exogeneous aldehydes and ketones as well as steroids.