Document Detail

Evidence for distinct dehydrogenase and isomerase sites within a single 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase protein.
MedLine Citation:
PMID:  1832298     Owner:  NLM     Status:  MEDLINE    
Complementary DNA encoding human 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3 beta-HSD) has been expressed in transfected GH4C1 with use of the cytomegalovirus promoter. The activity of the expressed protein clearly shows that both dehydrogenase and isomerase enzymatic activities are present within a single protein. However, such findings do not indicate whether the two activities reside within one or two closely related catalytic sites. With use of [3H]-5-androstenedione, the intermediate compound in dehydroepiandrosterone (DHEA) transformation into 4-androstenedione by 3 beta-HSD, the present study shows that 4MA (N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxamide) and its analogues inhibit DHEA oxidation competitively while they exert a noncompetitive inhibition of the isomerization of 5-androstenedione to 4-androstenedione with an approximately 1000-fold higher Ki value. The present results thus strongly suggest that dehydrogenase and isomerase activities are present at separate sites on the 3 beta-HSD protein. In addition, using 5 alpha-dihydrotestosterone (DHT) and 5 alpha-androstane-3 beta, 17 beta-diol as substrates for dehydrogenase activity only, we have found that dehydrogenase activity is reversibly and competitively inhibited by 4MA. Such data suggest that the irreversible step in the transformation of DHEA to 4-androstenedione is due to a separate site possessing isomerase activity that converts the 5-ene-3-keto to a much more stable 4-ene-3-keto configuration.
V Luu-The; M Takahashi; Y de Launoit; M Dumont; Y Lachance; F Labrie
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochemistry     Volume:  30     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1991 Sep 
Date Detail:
Created Date:  1991-10-17     Completed Date:  1991-10-17     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  8861-5     Citation Subset:  IM    
MRC Group in Molecular Endocrinology, CHUL Research Center, Quebec, Canada.
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MeSH Terms
Androgen Antagonists / pharmacology
Androstane-3,17-diol / metabolism
Azasteroids / pharmacology
Binding Sites
Binding, Competitive
Cell Line
Dehydroepiandrosterone / metabolism
Dihydrotestosterone / analogs & derivatives,  pharmacology
Multienzyme Complexes / antagonists & inhibitors,  chemistry*
Placenta / enzymology
Progesterone Reductase / antagonists & inhibitors,  chemistry*
Protein Conformation
Steroid Isomerases / antagonists & inhibitors,  chemistry*
Substrate Specificity
Tumor Cells, Cultured
Reg. No./Substance:
0/3 beta-hydroxysteroid oxidoreductase-delta(5) 3-ketosteroid isomerase; 0/Androgen Antagonists; 0/Azasteroids; 0/Multienzyme Complexes; 13647-35-3/trilostane; 25126-76-5/Androstane-3,17-diol; 521-18-6/Dihydrotestosterone; 53-43-0/Dehydroepiandrosterone; 73671-86-0/17-N,N-diethylcarbamoyl-4-methyl-4-azaandrostane-3-one; EC Reductase; EC 5.3.3.-/Steroid Isomerases

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