Rat NAD+-dependent 3alpha-hydroxysteroid dehydrogenase (AKR1C17): a member of the aldo-keto reductase family highly expressed in kidney cytosol.
Mammalian 3alpha-hydroxysteroid dehydrogenases (3alpha-HSDs) have been divided into two types: Cytosolic NADP(H)-dependent 3alpha-HSDs belonging to the aldo-keto reductase family, and mitochondrial and microsomal NAD(+)-dependent 3alpha-HSDs belonging to the short-chain dehydrogenase/reductase family. In this study, we characterized a rat aldo-keto reductase (AKR1C17), whose functions are unknown. The recombinant AKR1C17 efficiently oxidized 3alpha-hydroxysteroids and bile acids using NAD(+) as the preferred coenzyme at an optimal pH of 7.4-9.5, and was inhibited by ketamine and organic anions. The mRNA for AKR1C17 was detected specifically in rat kidney, where the enzyme was more highly expressed as a cytosolic protein than NADP(H)-dependent 3alpha-HSD (AKR1C9). Thus, AKR1C17 represents a novel NAD(+)-dependent type of cytosolic 3alpha-HSD with unique inhibitor sensitivity and tissue distribution. In addition, the replacement of Gln270 and Glu276 of AKR1C17 with the corresponding residues of NADP(H)-dependent 3alpha-HSD resulted in a switch in favor of NADP(+) specificity, suggesting their key roles in coenzyme specificity.
Sanai
Masaharu
M
Laboratory of Biochemistry, Gifu Pharmaceutical University, Mitahora-higashi, Gifu 502-8585, Japan.
Endo
Satoshi
S
Matsunaga
Toshiyuki
T
Ishikura
Shuhei
S
Tajima
Kazuo
K
El-Kabbani
Ossama
O
Hara
Akira
A
D015089:20-Hydroxysteroid Dehydrogenases / Q000096:biosynthesis / Q000737:chemistry*; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific) / Q000096:biosynthesis* / Q000737:chemistry*; D000818:Animals; D003600:Cytosol / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007658:Ketone Oxidoreductases / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity
D015089:20-Hydroxysteroid Dehydrogenases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D007658:Ketone Oxidoreductases