Biomaterial Database

Bifunctional enzyme activity at the same active site: competitive inhibition kinetics with 3 alpha/20 beta-hydroxysteroid dehydrogenase. 1980

F Sweet, and R Ahmed, and T E Morgan, and B C Sweet

20 beta-Hydroxy-5 alpha-pregnan-3-one (HPO) is a competitive inhibitor of reduction by 3 alpha/20 beta-hydroxysteroid dehydrogenase (3 alpha/20 beta-HSD; E.C.1.1.1.53) of 17 beta-hydroxy-5 alpha-androstan-3-one (DHT; 3 alpha-activity; Ki = 4.6x10(-5)M), and of 6 beta-acetoxyprogesterone (6 beta-AP; 20 beta-activity; Ki = 4.34x10(-5)M). HPO and DHT inhibit affinity alkylation of 3 alpha/20 beta-HSD by 6 beta-bromoacetoxyprogesterone (6 beta-BAP). The facts that 1) enzyme 3 alpha-activity and 20 beta-activity are both competitively inhibited by HPO with practically identical Ki-values, 2) 6 beta-BAP is solely a 20 beta-activity substrate for 3 alpha/20 beta-HSD, 3) one mole of 6 beta-BAP reacts with one mole of 3 alpha/20 beta-HSD to simultaneously inactivate 3 alpha- and 20 beta-activity, and 4) inactivation of 3 alpha/20 beta-HSD by 6 beta-BAP is inhibited by DHT (a C19-steroid) or HPO (a C21-steroid), support the view that the same active site of 3 alpha/20 beta-HSD possesses both 3 alpha- and 20 beta-activity. Bifunctional activity at the same active site is considered for other steroid-specific enzymes in female mammalian reproductive systems.

UI	MeSH Term	Description	Entries
D007536	Isomerism	The phenomenon whereby certain chemical compounds have structures that are different although the compounds possess the same elemental composition. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)	Isomerisms
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D011280	Pregnanolone	A pregnane found in the urine of pregnant women and sows. It has anesthetic, hypnotic, and sedative properties.	Eltanolone,3 alpha, 5 beta-Tetrahydroprogesterone,3 alpha-Hydroxy-5 alpha-pregnan-20-one,3 alpha-Hydroxy-5 beta-pregnan-20-one,3-Hydroxypregnan-20-one,3beta-Hydroxy-5alpha-pregnan-20-one,Allopregnan-3 beta-ol-20-one,Allopregnanolone,Epipregnanolone,Pregnan-3alpha-ol-20-one,Pregnanolone, (3alpha)-isomer,Pregnanolone, (3alpha, 5beta, 17-alpha)-isomer,Pregnanolone, (3alpha,5alpha)-isomer,Pregnanolone, (3alpha,5beta)-isomer,Pregnanolone, (3beta)-isomer,Pregnanolone, (3beta, 5alpha)-isomer,Pregnanolone, (3beta, 5alpha, 17alpha)-isomer,Pregnanolone, (3beta, 5alpha, 8alpha, 17beta)-isomer,Pregnanolone, (3beta, 5beta)-isomer,Pregnanolone, (3beta, 5beta, 17alpha)-isomer,Pregnanolone, (3beta, 5beta,14beta)-isomer,Pregnanolone, (5alpha)-isomer,Sepranolone,3 Hydroxypregnan 20 one,3 alpha Hydroxy 5 alpha pregnan 20 one,3 alpha Hydroxy 5 beta pregnan 20 one,3 alpha, 5 beta Tetrahydroprogesterone,3beta Hydroxy 5alpha pregnan 20 one,Allopregnan 3 beta ol 20 one,Pregnan 3alpha ol 20 one,alpha-Hydroxy-5 alpha-pregnan-20-one, 3,alpha-Hydroxy-5 beta-pregnan-20-one, 3,alpha-pregnan-20-one, 3 alpha-Hydroxy-5,beta-ol-20-one, Allopregnan-3,beta-pregnan-20-one, 3 alpha-Hydroxy-5
D003348	Cortisone	A naturally occurring glucocorticoid that has been used in replacement therapy for ADRENAL INSUFFICIENCY and as an anti-inflammatory agent. Cortisone itself is inactive; it is converted in the liver to the active metabolite HYDROCORTISONE. (From Martindale, The Extra Pharmacopoeia, 30th ed, p726)	17-Hydroxy-3,11,20-trioxopregn-4-en-21-yl acetate,Adreson,Cortisone Acetate,Cortone Acetate
D003349	Cortisone Reductase	An enzyme that catalyzes the interconversion of a ketone and hydroxy group at C-20 of cortisone and other 17,20,21-trihydroxy steroids. EC 1.1.1.53.	20-beta-Hydroxysteroid Dehydrogenase,3 alpha,20 beta Hydroxysteroid Dehydrogenase,20 beta Hydroxysteroid Dehydrogenase,Dehydrogenase, 20-beta-Hydroxysteroid,Reductase, Cortisone
D006908	Hydroxyprogesterones	Metabolites or derivatives of PROGESTERONE with hydroxyl group substitution at various sites.
D001667	Binding, Competitive	The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements.	Competitive Binding
D013196	Dihydrotestosterone	A potent androgenic metabolite of TESTOSTERONE. It is produced by the action of the enzyme 3-OXO-5-ALPHA-STEROID 4-DEHYDROGENASE.	5 alpha-Dihydrotestosterone,Androstanolone,Stanolone,17 beta-Hydroxy-5 beta-Androstan-3-One,17beta-Hydroxy-5alpha-Androstan-3-One,5 beta-Dihydrotestosterone,5-alpha Dihydrotestosterone,5-alpha-DHT,Anaprotin,Andractim,Dihydroepitestosterone,Gelovit,17 beta Hydroxy 5 beta Androstan 3 One,17beta Hydroxy 5alpha Androstan 3 One,5 alpha DHT,5 alpha Dihydrotestosterone,5 beta Dihydrotestosterone,Dihydrotestosterone, 5-alpha,beta-Hydroxy-5 beta-Androstan-3-One, 17
D013257	Steroids, Brominated	Steroids which are substituted with one or more bromine atoms in any position.	Brominated Steroids
D013302	Streptomyces	A genus of bacteria that form a nonfragmented aerial mycelium. Many species have been identified with some being pathogenic. This genus is responsible for producing a majority of the ANTI-BACTERIAL AGENTS of practical value.