Inhibition of 3 α/β,20β-Hydroxysteroid Dehydrogenase by Dexamethasone, Glycyrrhetinic Acid and Spironolactone Is Attenuated by Deletion of 12 Carboxyl-Terminal Residues

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We constructed a pig 3α/β,20β-hydroxysteroid dehydrogenase (3α/β,20β-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 3α/β,20β-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 3α/β,20β-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 (K_i) of pig 3α/β,20β-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.
公益社団法人日本薬学会の論文
2002-09-01