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PubMed1992

Intrauterine position effects on steroid metabolism and steroid receptors of reproductive organs in male mice.

Mice differ in their adult reproductive characteristics as a function of whether they developed in utero between two male fetuses (2M males), which have higher testosterone levels, or between two female fetuses (0M males), which have higher estradiol levels. The present study was designed to further characterize biochemical parameters of 2M and 0M adult male mice. Activities of testicular steroidogenic enzymes, namely delta 5-3 beta-hydroxysteroid dehydrogenase/isomerase, 17 alpha-hydroxylase, and C17,20-lyase (C21SCC P450), were measured by means of radiometric assays and HPLC fractionation of substrate and products. Activity of 5 alpha-reductase in both seminal vesicle and prostate was measured by similar techniques. Estrogen and androgen receptor concentrations, which indicate capacity to respond to steroid hormones, were also examined in the accessory sex organs. For both seminal vesicle and prostate, 5 alpha-reductase activities were approximately 60% greater in 2M males than in 0M males, indicating greater capacity to form dihydrotestosterone from testosterone in organs from 2M mice. No significant differences were found in testicular steroidogenic enzymes between 2M and 0M animals, whereas the trend for all three activities was higher for 2M males than for 0M males. While no differences were found in estrogen receptor concentrations, 0M prostates had three times the concentration of androgen receptors (occupied receptors) compared to 2M prostates. Our findings suggest that intrauterine fetal position exerts a significant influence on subsequent adult androgen metabolism and androgen responsiveness in reproductive organs of adult male mice.

Aldehyde-Lyases↗

PubMed1991

Delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity in two distinct density Leydig cells from immature rats. Differences in responsiveness to human chorionic gonadotropin or 8-bromoadenosine 3',5'-monophosphate.

The present studies examined the responsiveness to human chorionic gonadotropin (hCG) or 8-bromoadenosine 3',5'-monophosphate (8-Br-cAMP) of delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity of cultured immature Band 2 (low density) or Band 3 (high density) Leydig cells isolated on Percoll gradients. Enzyme activity increased in relation to the dose of hCG or 8-Br-cAMP in both bands; however, activity in Band 2 cells increased about 200% above control, while activity in Band 3 cells increased only about 30-60% above control following 6 days of treatment. Maximal responses were observed 4-6 days following exposure to hCG or 8-Br-cAMP in both bands. Because elevated 5 alpha-reductase activity prevents testosterone accumulation in immature Leydig cells, Band 2 or Band 3 cells were cultured in the presence of 4-methyl-4-aza-3-oxo-pregnan-(20S)-carboxylate, a 5 alpha-reductase inhibitor, to assess the relationship between changes in delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity and testosterone formation. Although hCG or 8-Br-cAMP-stimulated delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity began to decline by day 8 or 10 of treatment, testosterone levels progressively increased for 10 days before declining in both bands. Thus, changes in enzyme activity did not strictly correlate with testosterone synthesizing capacity of cultured Leydig cells. Enzyme activity also was measured in cells cultured with the 5 alpha-reductase inhibitor to determine whether the responsiveness of delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity of Band 2 or Band 3 cells was due, in part, to low testosterone levels. delta 5-3 beta-Hydroxysteroid dehydrogenase-isomerase activity in Band 2 or Band 3 cells cultured without or with the inhibitor was similar, suggesting that testosterone does not inhibit the enzyme in immature Leydig cells. The greater responsiveness of delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity in Band 2 cells was not due to Leydig cell replication as neither total DNA or [3H]thymidine incorporation into DNA was altered by hCG or cAMP.

5-alpha Reductase Inhibitors↗

PubMed1993

Stage-related changes in steroid-converting enzyme activities in Squalus testis: synthesis of biologically active metabolites via 3 beta-hydroxysteroid dehydrogenase/isomerase and 5 alpha-reductase.

To investigate the relationship between steroidogenesis and spermatogenesis, two key enzymes of androgen biosynthesis, 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) and 5 alpha-reductase, were compared at premeiotic (PrM), meiotic (M), and postmeiotic (PoM) stages. Staged tissues were obtained by dissection from the testis of the spiny dogfish Squalus acanthias, in which spermatogenesis is a simple diametric progression. Microsomal 3 beta-HSD activity was measured by conversion of [3H]dehydroepiandrosterone (DHEA) to androstenedione (AE). Reaction constants were: Km = 3.2 microM and Vmax = 243 pmol/min/mg protein. 3 beta-HSD increased progressively with maturation, resulting in three- to four-fold higher levels in PoM than in PrM stages. Absolute values and stage-related differences were the same, whether microsomes were derived from whole testis or from isolated spermatocysts (germ cell/Sertoli cell units), thus supporting microscopic studies showing that Sertoli cells are the primary steroidogenic elements of dogfish testis. In vitro conversion of [3H]testosterone to [3H]dihydrotestosterone (DHT) was used to estimate 5 alpha-reductase activity. Apparent substrate affinity was similar to that of 3 beta-HSD (Km = 2.9 microM), but maximal product yields were two to three orders of magnitude lower (Vmax = 208 fmol/min/mg protein). Also, the stage-related pattern of 5 alpha-reductase activity (PrM > PoM >> M) differed from that of 3 beta-HSD (PoM >> M > PrM).(ABSTRACT TRUNCATED AT 250 WORDS)

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1982

Rabbit hepatic progesterone 21-hydroxylase exhibits a bimodal distribution of activity.

Progesterone 21-hydroxylase activity varies extensively among liver microsomes prepared from individual New Zealand White (NZW) rabbits. The 21-hydroxylase activities are distributed between two groupings that differ by more than tenfold in mean activity. Both male and female animals are represented in the two groupings. However, females exhibited the higher activity more frequently than males. The 21-hydroxylation of progesterone is catalyzed by one of the liver microsomal cytochrome P-450 isozymes, form 1, and these differences in activity are suggestive of differences in the occurrence of this isozyme among NZW rabbits.

Animals↗

PubMed1995

Expression and characterization of isoforms of 3 beta-hydroxysteroid dehydrogenase/delta 5-->4-isomerase in the hamster.

The enzyme 3 beta-hydroxysteroid dehydrogenase/delta 5-->4-isomerase (3 beta-HSD) is essential for the production of all classes of steroid hormones. Multiple isozymes of this enzyme have been demonstrated in the kidney and liver of both the rat and the mouse, although the function of the enzyme in these tissues is unknown. We have characterized three isozymes of 3 beta-HSD expressed in various tissues of the hamster. Both western and northern blot analyses demonstrated very high levels of 3 beta-HSD in the adrenal, kidney and male liver. Conversely, there were extremely low levels of enzyme expression in the female liver. cDNA libraries prepared from RNA isolated from hamster adrenal, kidney and liver were screened with a full-length cDNA encoding human type 1 3 beta-HSD. Separate cDNAs encoding three isoforms of 3 beta-HSD were isolated from these libraries. To examine the properties of the isoforms, the cDNAs were ligated into expression vectors for over-expression in 293 human fetal kidney cells. The type 1 isoform, isolated from an adrenal cDNA library, was identified as a high-affinity 3 beta-hydroxysteroid dehydrogenase. A separate isoform, designated type 2, was isolated from the kidney, and this was also a high-affinity dehydrogenase/isomerase. Two cDNAs were isolated from the liver, one identical in sequence to type 2 of the kidney, and a distinct cDNA encoding an isoform designated type 3. The type 3 3 beta-HSD possessed no steroid dehydrogenase activity but was found to function as a 3-ketosteroid reductase. Thus male hamster liver expresses a high-affinity 3 beta-HSD (type 2) and a 3-ketosteroid reductase (type 3), whereas the kidney of both sexes express the type 2 3 beta-HSD isoform. These differ from the type 1 3 beta-HSD expressed in the adrenal cortex.

Amino Acid Sequence↗

PubMed2003

Steroidogenic isoenzymes in human hair and their potential role in androgenetic alopecia.

Androgenetic alopecia (AGA) is the most common type of hair loss. The relatively strong concordance of the degree of baldness in fathers and sons is not consistent with a simple Mendelian trait, and a polygenic basis is considered to be most likely. So far, the predisposing genes for AGA are unknown and we do not understand the molecular steps involved in androgen-dependent beard growth versus androgen-dependent hair loss, but AGA can be defined as a dihydrotestosterone (DHT)-dependent process with continuous miniaturization of sensitive hair follicles. The type 2 5alpha-reductase plays a central role by the intrafollicular conversion of testosterone to DHT. However, due to the increasing knowledge in this field, we now know that there are many more steroidogenic enzymes involved in the onset and development of AGA, and this article shall provide a critical overview of recent discoveries.

Alopecia↗

PubMed1994

Inborn errors of metabolism with consequences for bile acid biosynthesis. A minireview.

Five inborn errors with consequences for bile acid biosynthesis have been described: 7-dehydrocholesterol 7-reductase deficiency, 3 beta-hydroxysteroid delta 5-oxidoreductase/isomerase deficiency, 3-oxo-delta 4-steroid 5 beta-reductase deficiency, sterol 27-hydroxylase deficiency (cerebrotendinous xanthomatosis), and peroxisomal disease(s) with absence of peroxisomes. Diagnosis and treatment of these very rare disorders are discussed. Bile acid therapy is important in most of these disorders and in the case of 3 beta-hydroxysteroid delta 5-oxidoreductase/isomerase deficiency and 3-oxo-delta 4-steroid 5 beta-reductase deficiency such therapy may save the life of the affected cholestatic infant. In the case of sterol 27-hydroxylase deficiency, early treatment with chenodeoxycholic acid may prevent the development of progressive neurological dysfunction, dementia, and ataxia. In the latter three cases early diagnosis and treatment is of utmost importance.

Bile Acids and Salts↗

PubMed1999

Induction of 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase type 1 gene transcription in human breast cancer cell lines and in normal mammary epithelial cells by interleukin-4 and interleukin-13.

Sex steroids play a crucial role in the development and differentiation of normal mammary gland as well as in the regulation of breast cancer growth. Local intracrine formation of sex steroids from inactive precursors secreted by the adrenals, namely, dehydroepiandrosterone and its sulfate, may regulate growth and function of peripheral target tissues, including the breast. Both endocrine and paracrine influences on the proliferation of human breast cancer cells are well recognized. Breast tumors harbor tumor-associated macrophages and tumor-infiltrating lymphocytes that secrete a wide spectrum of cytokines. These factors may also contribute to neoplastic cell activity. The present study was designed to investigate the action of cytokines on 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity, which is an essential step in the biosynthesis of active estrogens and androgens in human breast cancer cell lines and in normal human mammary epithelial cells in primary culture. 3Beta-HSD activity was undetectable in ZR-75-1 and T-47D estrogen receptor-positive (ER)+ cells under basal growth conditions. This activity was markedly induced after exposure to picomolar concentrations of interleukin (IL)-4 or IL-13. The potent stimulatory effect of these cytokines on 3beta-HSD activity was also observed in the ER- MDA-MB-231 human breast cancer cell line and in normal human mammary epithelial cells (HMECs) in primary culture. The stimulation of 3beta-HSD activity by IL-4 and IL-13 results from a rapid increase in 3beta-HSD type 1 mRNA levels as measured by RT-PCR and Northern blot analyses. Such an induction of the 3beta-HSD activity may modulate androgenic and estrogenic biological responses as demonstrated using ZR-75-1 cells transfected with androgen- or estrogen-sensitive reporter constructs and treated with the adrenal steroid 5-androstene-3beta,17beta-diol. The DNA-binding activity of Stat6, a member of the signal transducers and activators of transcription gene family, is activated 30 min after exposure to IL-4 and IL-13 in human breast cancer cell lines as well as in HMECs in primary culture. In these cells, Stat6 activated by IL-4 or IL-13 binds to two regions of the 3beta-HSD type 1 gene promoter, containing Stat6 consensus sequences. IL-4 induction of 3beta-HSD mRNA and activity is sensitive to staurosporine. This protein kinase inhibitor also inhibits IL-4-induced Stat6 DNA-binding activity. Our data demonstrate for the first time that IL-4 and IL-13 induce 3beta-HSD type 1 gene expression, thus suggesting their involvement in the fine control of sex steroid biosynthesis from adrenal steroid precursors in normal and tumoral human mammary cells. Furthermore, aromatase and/or 5alpha-reductase(s) are expressed in the mammary gland and in a large proportion of human breast tumors. An increase in the formation of their substrates, namely, 4-androstenedione and testosterone, may well have a significant impact on the synthesis of active estrogens and androgens in these tissues.

Androstenediol↗

PubMed2004

Progesterone enhances motor, anxiolytic, analgesic, and antidepressive behavior of wild-type mice, but not those deficient in type 1 5 alpha-reductase.

The importance of progesterone's (P(4)) metabolism by the 5 alpha-reductase type I enzyme was examined in homozygous and heterozygous 5 alpha-reductase type I knockout mice and their wild-type siblings. P(4) (1.0 mg) or vehicle was administered and effects on motor, anxiety, nociceptive, and depression behavior were observed. After testing, whole-brain progesterone and 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha,5 alpha-THP) levels were determined by radioimmunoassay. Motor behavior in the horizontal crossing and open field tasks of 5 alpha-reductase-deficient mice administered P(4) was similar to vehicle control mice and significantly reduced compared to wild-type mice administered P(4). In the open field, 5 alpha-reductase-deficient mice administered P(4) had a similar number of central entries as did vehicle control mice, both were lower than central entries of P(4)-administered wild-type mice. However, in the plus maze, P(4) to 5 alpha-reductase-deficient or wild-type mice significantly increased open arm activity compared to vehicle-administered control mice. P(4) to wild-type, but not 5 alpha-reductase-deficient mice, significantly increased latencies to lick front and back paws in response to radiant heat stimuli compared to vehicle administration to control mice. In the forced swim test, 5 alpha-reductase-deficient mice administered P(4) were similar to vehicle control mice and the latency to immobility was significantly decreased, and the duration of immobility was significantly increased, compared to wild-type mice administered P(4). Thus, these data suggest metabolism by the 5 alpha-reductase type I enzyme may mitigate P(4)'s effects on some tasks of motor, anxiety, nociception, and depression behavior.

Animals↗

PubMed1990

Inhibitory effect of synthetic progestins, 4-MA and cyanoketone on human placental 3 beta-hydroxysteroid dehydrogenase/5----4-ene-isomerase activity.

Human placental 3 beta-hydroxysteroid dehydrogenase/5----4-ene isomerase (3 beta-HSD) purified from human placenta transforms C-21 (pregnenolone and 17 alpha-hydroxy pregnenolone) as well as C-19 (dehydroepiandrosterone and androst-5-ene-3 beta, 17 beta-diol) steroids into the corresponding 3-keto-4-ene-steroids and is thus involved in the biosynthesis of all classes of hormonal steroids. Trilostane, epostane and cyanoketone are potent inhibitors of 3 beta-HSD with Ki values of approximately 50 nM. 4-MA, a well known 5 alpha-reductase inhibitor, is also a potent inhibitor of 3 beta-HSD with a Ki value of 56 nM. Synthetic progestin compounds such as promegestone and RU2323 show relatively strong inhibitory effects with Ki values of 110 and 190 nM, respectively. Cyproterone acetate, a progestin used in the treatment of hirsutism, acne and prostate cancer as well as norgestrel and norethindrone that are widely used as oral contraceptives also inhibit 3 beta-HSD activity at Ki values of 1.5, 1.7 and 2.5 microM, respectively.

3-Hydroxysteroid Dehydrogenases↗

PubMed2002

In vitro hCG and human recombinant FSH actions on testicular steroidogenesis in the toad Bufo arenarum.

In order to study the regulation of testicular steroidogenesis in the toad Bufo arenarum, the effect of gonadotropins (hCG and hrFSH) on steroidogenic enzymes was determined using an in vitro system. 3beta-Hydroxysteroid dehydrogenase/isomerase activity was not affected by any of the gonadotropins, at any of the concentrations used. In contrast, 5alpha-reductase activity was strongly reduced by both hCG and hrFSH. Human chorionic gonadotropin inhibited the activity of cytochrome P450 17alpha-hydroxylase-C(17-20) lyase (P450(c17)), only at the highest concentration used, while hrFSH strongly reduced P450(c17) activity at all the doses assayed. In conclusion, these data suggest that LH (hCG) and FSH regulate steroidogenic enzymes such as 5alphaRed and P450(c17). The results also suggest that FSH could be involved in the regulation of the change in steroidogenesis undergone by the testis during the breeding season. In turn, the inhibition of P450(c17) activity could result in a reduction of androgen production and an increment of C21 steroids.

Animals↗

PubMed2005

Bile acid biosynthesis during liver regeneration: enzyme activities of cholesterol 7alpha-hydroxylase and 3beta-hydroxy-delta5-C27-steroid dehydrogenase in rats.

The effects of two-thirds partial hepatectomy on bile acid metabolism have not been well established. This study investigated the changes in microsomal enzymes activities during liver regeneration. The cholesterol 7alpha-hydroxylase (7alpha-hydroxylase) and 3beta-hydroxy-delta5-C27-steroid dehydrogenase (3beta-dehydrogenase) activities in male Wistar rats were determined using high-performance liquid chromatography (HPLC). Cytochrome P450 (P450) and cytochrome b5 (b5) levels and NADPH cytochrome c reductase activities were also determined after hepatectomy. 7alpha-Hydroxylase activities were not reduced on days 3, 5, or 7 compared to those of sham-operated rats, but there was a significant decrease (by 60%) of 3beta-dehydrogenase activity compared to that of sham-operated groups (p <0.01) on days 3, 5, and 7 after hepatectomy. While 7alpha-hydroxylase activity had recovered by day 3 after hepatectomy, 3beta-dehydrogenase activity had not, even on day 7. These results suggest that the mechanisms of regulation of these 2 bile acid metabolizing enzymes are significantly different during liver regeneration.

Animals↗

PubMed1998

Characterization of cDNAs encoding isoforms of hamster 3 beta-hydroxysteroid dehydrogenase/delta 5-->4 isomerase.

Western blot analyses of various hamster tissues reveal high levels of expression of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in adrenal and liver, and moderate levels of expression in kidney. The expression in liver is sexually dimorphic; very high levels of protein are observed in adult male liver but very low levels are seen in the female liver. Three distinct cDNAs encoding isoforms of 3 beta-HSD were isolated from hamster cDNA libraries. The type 1 isoform is a high-affinity dehydrogenase/isomerase expressed in adrenal and male kidney. The type 2 isoform is also a high-affinity dehydrogenase/isomerase expressed in kidney and male liver. The type 3 enzyme is a 3-ketosteroid reductase expressed predominantly in kidney. Sequencing of the clones showed that all three are structurally very similar, although types 1 and 2 share the greatest degree of similarity. Immunohistochemical staining for 3 beta-HSD in the adrenal was found throughout the adrenal cortex. In the kidney staining was confined to tubules, and in the liver, heavy staining was found in hepatocytes. The cloning of cDNAs for 3 beta-HSD from the liver and kidney should help in elucidating the function of this enzyme in these tissues.

Adrenal Glands↗

PubMed1997

Isolation of a new mouse 3beta-hydroxysteroid dehydrogenase isoform, 3beta-HSD VI, expressed during early pregnancy.

The enzyme 3beta-hydroxysteroid dehydrogenase (3beta-HSD) is a key enzyme in the biosynthesis of steroid hormones. To date, this laboratory has isolated and characterized five distinct 3beta-HSD complementary DNAs (cDNAs) in the mouse (3beta-HSD I through V). These different forms are expressed in a tissue- and developmentally-specific manner and fall into two functionally distinct enzymes. 3beta-HSD I and III, and most likely II, function as dehydrogenase/isomerases, whereas 3beta-HSD IV and V function as 3-ketosteroid reductases. This study describes the isolation, characterization, and tissue-specific expression of a sixth member of this gene family, 3beta-HSD VI. This new isoform functions as an NAD+-dependent dehydrogenase/isomerase exhibiting very low Michaelis-Menten constant (Km) values for pregnenolone (approximately 0.035 microM) and dehydroepiandrosterone (approximately 0.12 microM). 3beta-HSD VI is the earliest isoform to be expressed during embryogenesis in cells of embryonic origin at 7 and 9.5 days postcoitum (pc), and is the major isoform expressed in uterine tissue at the time of implantation (4.5 days pc) and continues to be expressed in uterine tissue at 6.5, 7.5, and 9.5 days pc. 3beta-HSD VI is expressed in giant trophoblasts at 9.5 days pc and is expressed in the placenta through day 15.5 pc. In the adult mouse, 3beta-HSD VI appears to be the only isoform expressed in the skin and also is expressed in the testis, but to a lesser extent than 3beta-HSD I. Mouse 3beta-HSD VI cDNA is orthologous to human 3beta-HSD I cDNA. Human type I 3beta-HSD has been shown to be the only isoform expressed in the placenta and skin. The demonstration that mouse 3beta-HSD VI functions as a dehydrogenase/isomerase and is the predominant isoform expressed during the first half of pregnancy in uterine tissue and in embryonic cells suggests that this isoform may be involved in local production of progesterone, which is needed for successful implantation of the blastocyst and/or maintenance of early pregnancy.

Adrenal Glands↗

PubMed2001

cDNA cloning and physical mapping of porcine 3 beta-hydroxysteroid dehydrogenase/Delta 5-Delta 4 isomerase.

The 3 beta-hydroxysteroid dehydrogenase/Delta 5-Delta 4-isomerase (3 beta-HSD) enzymes are essential for the biosynthesis of steroid hormones. The 3 beta-HSD gene family has been reported to encode for different isoenzymes which function either as dehydrogenase/isomerase or as reductase. The 3 beta-HSD enzymes are involved in the formation of the pheromone androstenone (5 alpha-androst-16-ene-3-one) which contributes to the unpleasant odour present in the meat of uncastrated boars. An reverse-transcription-polymerase chain reaction (RT-PCR) probe from porcine testicular tissue of a 3 beta-HSD enzyme was used to screen a porcine adipose tissue cDNA library. Both strands of the positive clones were sequenced and the putative coding sequence of 1122 nucleotides encodes 374 amino acids. Comparison of the putative open reading frame with the bovine and the human type I homologues revealed 85.6 and 79.3% identity, respectively. Fluorescence in situ hybridization (FISH) was performed with a labelled PAC clone containing the gene of interest. The 3 beta-HSD gene was mapped to the porcine chromosome 4q16-4q21 which is in accordance with the comparative gene map.

Amino Acid Sequence↗

PubMed1984

Maximal testosterone production in Leydig cells from inbred mice relates to the activity of 3 beta-hydroxysteroid dehydrogenase-isomerase.

We previously described significant differences in maximal testosterone production by Leydig cells from the following strains of inbred mice: C57BL/10J, C57BL/6J, DBA/2J, and C3H/HeJ. To evaluate whether these differences in maximal testosterone production related to the activities of the steroidogenic enzymes of the smooth endoplasmic reticulum of Leydig cells from these strains, the activities of 3 beta-hydroxysteroid dehydrogenase-isomerase, 17 alpha-hydroxylase, C17-20 lyase, and 17-ketosteroid reductase were measured in homogenates of purified Leydig cells using 3H-labeled substrates and measuring the amounts of 3H products formed. Maximal and basal testosterone production were determined by incubating aliquots of Leydig cells for 2 h in the presence or absence of 30 pM hCG. Maximal testosterone production by Leydig cells from C57BL/10J and C57BL/6J mice was significantly greater than that by Leydig cells from DBA/2J and C3H/HeJ mice. No difference in basal testosterone production was observed among the strains. Among the four enzymes studied, only 3 beta-hydroxysteroid dehydrogenase-isomerase activity was significantly correlated with hCG-stimulated testosterone production by Leydig cells from the four strains of mice. In addition, when equivalent numbers of Leydig cells from each strain were incubated with an equal concentration of [3H]pregnenolone, a similar difference in [3H] testosterone production was observed among the four strains, as was seen with hCG-stimulation. Leydig cells from C57BL/10 and C57BL/6J mice left less [3H]pregnenolone unmetabolized and produced higher amounts of [3H]testosterone than Leydig cells from DBA/2J and C3H/HeJ mice. There was a significant negative correlation between the amount of pregnenolone unmetabolized and the amount of testosterone produced. These data suggest that 3 beta-hydroxysteroid dehydrogenase-isomerase may be important in determining the differences in hCG-stimulated testosterone production by Leydig cells from the four strains of mice.

3-Hydroxysteroid Dehydrogenases↗

PubMed1995

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.

3-Hydroxysteroid Dehydrogenases↗

PubMed1994

Formation and degradation of dihydrotestosterone by recombinant members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase family.

The structures of cDNA clones encoding four members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) family were characterized. The rat type I, type II and the novel type IV are genuine NAD+/H-dependent 3 beta-HSD isoenzymes. On the other hand, the liver-specific type III protein is a specific 3-keto-reductase (3-KSR) that catalyzes the conversion of 5 alpha-androstane-3-one-17 beta-ol (DHT) and 5 alpha-androstane 3,17-dione (A-dione) into their 3 beta-hydroxy metabolites. The aim of the present study was to further characterize the enzymatic properties of rat types I, III and IV, especially their role in the formation and degradation of DHT after transient expression in intact human HeLa cervical carcinoma, JEG-3 choriocarcinoma or SW-13 adrenal cortex adenocarcinoma cells in culture. The expressed type III 3-KSR in intact HeLa cells catalyzed the reduction of DHT into 3 beta-diol, whereas expression of type I 3 beta-HSD in these cell lines had no significant effect on the basal conversion of DHT into 3 beta-diol, but it did increase the formation of DHT from 3 beta-diol. A-dione is the predominant product obtained when DHT and 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol) are used as substrates in intact JEG-3 and SW-13 cells transfected with rat type I 3 beta-HSD. Furthermore, this predominant 17 beta-HSD activity was also observed in SW-13 cells transfected with the novel rat type IV 3 beta-HSD. The predominance of this 'secondary' 17 beta-HSD activity is also reflected in HeLa cells transfected with type I 3 beta-HSD by the deduced predominant pathway 3 beta-diol-->DHT-->5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol)-->androsterone (ADT), in which formation of 3 alpha-HSD activity of HeLa cells, whereas the other reactions are catalyzed by the type I 3 beta-HSD isoenzyme. This observation thus demonstrates that rat type I 3 beta-HSD may also catalyze the conversion of 3 alpha-diol into ADT through its intrinsic 17 beta-HSD activity. The predominant metabolic pathways observed in the present study could be attributed to preponderant bioavailability of NAD+ and NADPH in the intact transfected cells used.

17-Hydroxysteroid Dehydrogenases↗