title: Inhibition of 3 alpha/beta,20 beta-hydroxysteroid dehydrogenase by dexamethasone, glycyrrhetinic acid and spironolactone is attenuated by deletion of 12 carboxyl-terminal residues.
abstract: We constructed a pig 3alpha/beta,20beta-hydroxysteroid dehydrogenase (3alpha/beta,20beta-HSD) mutant, which lacks 12 carboxyl-terminal amino acids residues. Enzyme activity studies indicated that the deleted amino acids have a role in steroid metabolism and may assist in substrate binding in wild-type 3alpha/beta,20beta-HSD. Furthermore, substrate binding likely induces a conformational change allowing the 12 carboxyl-terminal amino acids interact with the steroid substrate [Nakajin S. et al., Biochim. Biophys. Acta, 1550, 175-182 (2001)]. In this paper, we clarified that although pig 3alpha/beta,20beta-HSD is potently inhibited by dexamethasone, glycyrrhetinic acid and spironolactone, this inhibition is remarkably attenuated by deleting the 12 carboxyl-terminal residues. The inhibition constant (Ki) of pig 3alpha/beta,20beta-HSD for dexamethasone increased 115-fold. These observations also indicate that these amino acid residues interact with steroid substrates or steroid inhibitors and have an important role in substrate or inhibitor binding to the active site.
authors.affiliation: Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Sugitani, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Itoda
authors.forename: Noriko
authors.initials: N
authors.lastname: Takase
authors.forename: Shizuo
authors.initials: S
authors.lastname: Nakajin
mesh_terms: D015089:20-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000596:Amino Acids / Q000235:genetics*; D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006034:Glycyrrhetinic Acid / Q000494:pharmacology*; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics*; D051381:Rats; D013148:Spironolactone / Q000494:pharmacology*; D013552:Swine
chemical_list: D000596:Amino Acids; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D013148:Spironolactone; D003907:Dexamethasone; D015089:20-Hydroxysteroid Dehydrogenases; C115140:3 alpha-beta, 20 beta-hydroxysteroid dehydrogenase; D006034:Glycyrrhetinic Acid