Structure-function relationships and molecular genetics of the 3 beta-hydroxysteroid dehydrogenase gene family.
The isoenzymes of the 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene-isomerase (3 beta-HSD) gene family catalyse the transformation of all 5-ene-3 beta-hydroxysteroids into the corresponding 4-ene-3-keto-steroids and are responsible for the interconversion of 3 beta-hydroxy- and 3-keto-5 alpha-androstane steroids. The two human 3 beta-HSD genes and the three related pseudogenes are located on the chromosome 1p13.1 region, close to the centromeric marker D1Z5. The 3 beta-HSD isoenzymes prefer NAD+ to NADP+ as cofactor with the exception of the rat liver type III and mouse kidney type IV, which both prefer NADPH as cofactor for their specific 3-ketosteroid reductase activity due to the presence of Tyr36 in the rat type III and of Phe36 in mouse type IV enzymes instead of Asp36 found in other 3 beta-HSD isoenzymes. The rat types I and IV, bovine and guinea pig 3 beta-HSD proteins possess an intrinsic 17 beta-HSD activity specific to 5 alpha-androstane 17 beta-ol steroids, thus suggesting that such "secondary" activity is specifically responsible for controlling the bioavailability of the active androgen DHT. To elucidate the molecular basis of classical form of 3 beta-HSD deficiency, the structures of the types I and II 3 beta-HSD genes in 12 male pseudohermaphrodite 3 beta-HSD deficient patients as well as in four female patients were analyzed. The 14 different point mutations characterized were all detected in the type II 3 beta-HSD gene, which is the gene predominantly expressed in the adrenals and gonads, while no mutation was detected in the type I 3 beta-HSD gene predominantly expressed in the placenta and peripheral tissues. The mutant type II 3 beta-HSD enzymes carrying mutations detected in patients affected by the salt-losing form exhibit no detectable activity in intact transfected cells, at the exception of L108W and P186L proteins, which have some residual activity (approximately 1%). Mutations found in nonsalt-loser patients have some residual activity ranging from approximately 1 to approximately 10% compared to the wild-type enzyme. Characterization of mutant proteins provides unique information on the structure-function relationships of the 3 beta-HSD superfamily.
Medical Research Council Group in Molecular Endocrinology, CHUL Research Center, Québec, Canada.
J
J
Simard
R
R
Sanchez
F
F
Durocher
E
E
Rhéaume
C
C
Turgeon
Y
Y
Labrie
V
V
Luu-The
F
F
Mebarki
Y
Y
Morel
Y
Y
de Launoit
D015096:3-Hydroxysteroid Dehydrogenases / Q000172:deficiency*; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002874:Chromosome Mapping; D004700:Endocrine System Diseases / Q000201:enzymology; D005260:Female; D005796:Genes; D006801:Humans; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism*; D017354:Point Mutation; D011375:Progesterone Reductase / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013251:Steroid Isomerases / Q000235:genetics* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014337:Trout
C021425:3 beta-hydroxysteroid oxidoreductase-delta(5) 3-ketosteroid isomerase; D007527:Isoenzymes; D009097:Multienzyme Complexes; D015096:3-Hydroxysteroid Dehydrogenases; D011375:Progesterone Reductase; D013251:Steroid Isomerases