title: Inhibition of Streptomyces hydrogenans 3 alpha,20 beta-hydroxysteroid dehydrogenase by licorice-derived compounds and crystallization of an enzyme-cofactor-inhibitor complex.
abstract: Streptomyces hydrogenans 3 alpha,20 beta-hydroxysteroid dehydrogenase reduces the C20 ketone on glucocorticoids and progestins. We find that two licorice-derived compounds, glycyrrhizic acid and carbenoxolone, inhibit this enzyme with microM Kis. Inhibition is competitive, indicating that these compounds are binding at or close to the catalytic site. Carbenoxolone's high aqueous solubility and affinity for 3 alpha,20 beta-hydroxysteroid dehydrogenase enabled us to prepare crystals of a carbenoxolone-NADH-enzyme ternary complex, which preliminary X-ray analysis indicates has a crystal structure that is significantly different from that of the 3 alpha,20 beta-hydroxysteroid dehydrogenase-NADH complex. A comparison of the tertiary structures of these two complexes should prove useful in understanding this enzyme's catalytic mechanism, as well as those of two homologous enzymes, mammalian 11 beta-hydroxysteroid dehydrogenase and 15-hydroxyprostaglandin dehydrogenase that also are inhibited by carbenoxolone.
authors.affiliation: Medical Foundation of Buffalo, Molecular Biophysics Department, NY 14203-1196.
authors.forename: D
authors.initials: D
authors.lastname: Ghosh
authors.forename: M
authors.initials: M
authors.lastname: Erman
authors.forename: W
authors.initials: W
authors.lastname: Pangborn
authors.forename: W L
authors.initials: WL
authors.lastname: Duax
authors.forename: M E
authors.initials: ME
authors.lastname: Baker
mesh_terms: D001665:Binding Sites; D002229:Carbenoxolone / Q000494:pharmacology*; D003067:Coenzymes; D003348:Cortisone / Q000378:metabolism; D003460:Crystallization; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D006035:Glycyrrhiza / Q000737:chemistry; D019695:Glycyrrhizic Acid; D006913:Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D010936:Plant Extracts / Q000494:pharmacology; D010946:Plants, Medicinal; D011374:Progesterone / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology*; D014961:X-Ray Diffraction
chemical_list: D003067:Coenzymes; D046911:Macromolecular Substances; D010936:Plant Extracts; D011374:Progesterone; D019695:Glycyrrhizic Acid; D006913:Hydroxysteroid Dehydrogenases; D002229:Carbenoxolone; D006034:Glycyrrhetinic Acid; D003348:Cortisone