1hdc
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(New page: 200px<br /><applet load="1hdc" size="450" color="white" frame="true" align="right" spinBox="true" caption="1hdc, resolution 2.20Å" /> '''MECHANISM OF INHIBIT...)
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Revision as of 14:24, 20 November 2007
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MECHANISM OF INHIBITION OF 3ALPHA,20BETA-HYDROXYSTEROID DEHYDROGENASE BY A LICORICE-DERIVED STEROIDAL INHIBITOR
Overview
BACKGROUND: Bacterial 3 alpha, 20 beta-hydroxysteroid dehydrogenase (3, alpha, 20 beta-HSD) reversibly oxidizes the 3 alpha and 20 beta hydroxyl, groups of androstanes and pregnanes and uses nicotinamide adenine, dinucleotide as a cofactor. 3 alpha, 20 beta-HSD belongs to a family of, short-chain dehydrogenases that has a highly conserved Tyr-X-X-X-Lys, sequence. The family includes mammalian enzymes involved in hypertension, digestion, fertility and spermatogenesis. Several members of the enzyme, family, including 3 alpha, 20 beta-HSD, are competitively inhibited by, glycyrrhizic acid, a steroidal compound found in licorice, and its, derivative, carbenoxolone, an anti-inflammatory glucocorticoid. RESULTS:, The three-dimensional structure of the enzyme-carbenoxolone complex has, been determined and refined at 2.2 A resolution to a crystallographic, R-factor of 19.4%. The hemisuccinate side chain of carbenoxolone makes a, hydrogen bond with the hydroxyl group of the conserved residue Tyr152 and, occupies the position of the nicotinamide ring of the cofactor. The, occupancies of the inhibitor in four independent catalytic sites refine to, 100%, 95%, 54% and 36%. CONCLUSIONS: The steroid binds at the catalytic, site in a mode much like the previously proposed mode of binding of the, substrate cortisone. No bound cofactor molecules were found. The varying, occupancy of steroid molecules observed in the four catalytic sites is, either due to packing differences or indicates a cooperative effect among, the four sites. The observed binding accounts for the inhibition of 3, alpha, 20 beta-HSD.
About this Structure
1HDC is a Single protein structure of sequence from Streptomyces exfoliatus with CBO as ligand. Active as 3-alpha-(or 20-beta)-hydroxysteroid dehydrogenase, with EC number 1.1.1.53 Full crystallographic information is available from OCA.
Reference
Mechanism of inhibition of 3 alpha, 20 beta-hydroxysteroid dehydrogenase by a licorice-derived steroidal inhibitor., Ghosh D, Erman M, Wawrzak Z, Duax WL, Pangborn W, Structure. 1994 Oct 15;2(10):973-80. PMID:7866748
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