Linked Life Data

9415401

Source:http://linkedlifedata.com/resource/pubmed/id/9415401

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
13
pubmed:dateCreated
1998-2-10
pubmed:abstractText
In androgen target tissues, 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) may regulate occupancy of the androgen receptor (AR) by catalyzing the interconversion of 5alpha-dihydrotestosterone (5alpha-DHT) (a potent androgen) and 3alpha-androstanediol (a weak androgen). In this study, a 3alpha-HSD cDNA (1170 bp) was isolated from a human prostate cDNA library. The human prostatic 3alpha-HSD cDNA encodes a 323-amino acid protein with 69.9%, 84.1%, 99.4%, and 87.9% sequence identity to rat liver 3alpha-HSD and human type 1, type 2, and type 3 3alpha-HSDs, respectively, and is a member of the aldo-keto reductase superfamily. The close homology with human type 2 3alpha-HSD suggests that it is either identical to this enzyme or a structural allele. Surprisingly, when the recombinant protein was expressed and purified from Escherichia coli, the enzyme did not oxidize androsterone when measured spectrophotometrically, an activity previously assigned to recombinant type 2 3alpha-HSD using this assay. Complete kinetic characterization of the purified protein using spectrophotometric, fluorometric, and radiometric assays showed that the catalytic efficiency favored 3alpha-androstanediol oxidation over 5alpha-DHT reduction. Using [14C]-5alpha-DHT as substrate, TLC analysis confirmed that the reaction product was [14C]-3alpha-androstanediol. However, in the reverse reaction, [3H]-3alpha-androstanediol was oxidized first to [3H]-androsterone and then to [3H]-androstanedione, revealing that the expressed protein possessed both 3alpha- and 17beta-HSD activities. The 17beta-HSD activity accounted for the higher catalytic efficiency observed with 3alpha-androstanediol. These findings indicate that, in the prostate, type 2 3alpha-HSD does not interconvert 5alpha-DHT and 3alpha-androstanediol but inactivates 5alpha-DHT through its 3-ketosteroid reductase activity. Levels of 3alpha-HSD mRNA were measured in primary cultures of human prostatic cells and were higher in epithelial cells than stromal cells. In addition, elevated levels of 3alpha-HSD mRNA were observed in epithelial cells derived from benign prostatic hyperplasia and prostate carcinoma tissues. Expression of 3alpha-HSD was not prostate specific, since high levels of mRNA were also found in liver, small intestine, colon, lung, and kidney. This study is the first complete characterization of recombinant type 2 3alpha-HSD demonstrating dual activity and cellular distribution in the human prostate.
pubmed:grant
pubmed:commentsCorrections
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0888-8809
pubmed:author
pubmed:issnType
Print
pubmed:volume
11
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1971-84
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Expression and characterization of recombinant type 2 3 alpha-hydroxysteroid dehydrogenase (HSD) from human prostate: demonstration of bifunctional 3 alpha/17 beta-HSD activity and cellular distribution.
pubmed:affiliation
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104-6084, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.