Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.1.1.3 (HSD)
3,464 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

3 beta-Hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase (3 beta HSD) is a NAD(+)-dependent membrane-bound enzyme that catalyzes the oxidation of delta 5-3 beta-hydroxysteroids to delta 4-3-keto structures during adrenal, gonadal, and placental steroidogenesis. Enzyme activity is located in both microsomes and mitochondria. In these experiments we examined the membrane topologies of 3 beta HSD in rat and calf adrenal microsomes and mitochondria by comparing access to the active sites of coenzyme and the inhibitor mersalyl, a nonpenetrant organic mercurial anion. Microsomal activity required exogenous NAD+ and was inhibited by mersalyl, indicating that the active site faced the medium in vitro and the cytoplasm in vivo. In contrast, mitochondrial 3 beta HSD used matrix space NAD+, was inhibited by reduction of intramitochondrial NAD(P)+, and was insensitive to mersalyl. Mitochondrial activity was decreased by exogenous NADH (apparent Ki, 2.8 microM) and increased by added NAD+ (apparent Ka, 2.4 microM). However, mersalyl blocked the effects of exogenous NADH and NAD+ and returned the activity to that observed before coenzyme addition. The membrane-sidedness of the NAD+ activation was examined further in submitochondrial particles prepared by sonication of pyridine nucleotide-depleted calf adrenal cortex mitochondria. Particles were prepared in the absence or presence of 10 mM NAD+ and contained none or 2.9-7.3 nmol NAD+/mg protein, respectively. Both groups of submitochondrial particles required exogenous NAD+ for 3 beta HSD activity, indicating that the active site faced the medium (the particles were everted), and the contained NAD+ was inside the particles. However, 3 beta HSD activity was increased 12-140% in particles that contained NAD+. The results suggest that mitochondrial 3 beta HSD is an integral inner membrane protein, that the active site faces the matrix space and is influenced by coenzyme availability, and that a regulatory site(s) faces the intermembrane space. Binding of NAD+ or NADH to this external site increases or decreases, respectively, the rate of catalysis at the active site. Mitochondrial 3 beta HSD activity may be enhanced by oxidation of intermembrane space NADH via an active rotenone- and antimycin-a-insensitive NADH oxidase.
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PMID:Topology of 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase in adrenal cortex mitochondria and microsomes. 829 70

During the follicular/luteal phase shift in steroidogenesis, follicular steroid production changes from predominantly estradiol and androgen secretion before the LH surge to decreased androgen and estrogen and increased progesterone after the LH surge. Our objective was to determine whether changes in progesterone production by the preovulatory follicle are effected via changes in mRNA levels for the steroidogenic enzymes cholesterol side-chain cleavage cytochrome P450 (P450scc) and 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta HSD). Bovine preovulatory follicles were obtained in the early follicular phase (n = 9 follicles), the midfollicular phase (n = 4), or the late follicular phase (after the LH surge, but before ovulation; n = 5). Total RNA extracted from granulosa cells and theca interna at the time of cell isolation or after 24 or 72 h of culture in control or LH-containing medium was subjected to Northern analysis, and autoradiographs were scanned densitometrically. P450scc mRNA levels in granulosa cells were high in the early follicular phase and decreased by 96% after the LH surge (P < 0.05). 3 beta HSD mRNA levels in granulosa cells were 4.2-fold higher in early vs. late follicular phase (P < 0.01). In theca interna, 3 beta HSD mRNA levels were 3.6- and 2.6-fold higher in the early vs. the mid- and late follicular phase (P < 0.05), but levels of P450scc mRNA did not differ significantly with stage of follicular development. After granulosa cells had been cultured for 24 h in control or LH-containing medium, P450scc and 3 beta HSD mRNA had declined dramatically compared to mRNA levels at the time of cell isolation during the early follicular phase (P < 0.01). However, after 72 h in control or LH-containing medium, an increase in P450scc and 3 beta HSD mRNA was observed relative to levels at 24 h (P < 0.01). After 72 h of culture, the signal for P450scc and 3 beta HSD mRNA in granulosa cells exposed to LH was higher than the signal detected in cultures without LH (P < 0.01). Similar changes in message for P450scc were observed in cultured thecal cells. Thus, the previously observed increases in production of progesterone by bovine theca interna and granulosa cells obtained after vs. before the LH surge cannot be explained by an increase in message for P450scc and 3 beta HSD.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Levels of messenger ribonucleic acid for cholesterol side-chain cleavage cytochrome P-450 and 3 beta-hydroxysteroid dehydrogenase in bovine preovulatory follicles decrease after the luteinizing hormone surge. 842 1

The enzyme 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-Isomerase (3 beta HSD) catalyzes the conversion of delta 5-3 beta-hydroxysteroids to delta 4-3-ketosteroids, an essential step in the biosynthesis of all biologically active steroid hormones. We previously reported the isolation of three distinct mouse cDNAs for 3 beta HSD (3 beta HSD I, II, and III) and tissue-specific expression of their mRNAs. 3 beta HSD I is expressed only in gonads and adrenal glands, and 3 beta HSD II and III are expressed in both liver and kidneys. In the current study, we present data which demonstrate that transiently expressed 3 beta HSD I and 3 beta HSD III proteins can catalyze the conversion of the delta 5-steroids, pregnenolone and dehydroepiandrosterone, to their respective delta 4-3-ketosteroids, progesterone and androstenedione. They also can dehydrogenate the 3 beta-hydroxy group of the 5 alpha-reduced steroid 5 alpha-androstanediol to yield dihydrotestosterone in the presence of the cofactor NAD+. The Km values of the expressed 3 beta HSD I (for each of these substrates) were all below 0.2 microM. Km values of 3 beta HSD III were greater for all substrates, with the greatest increase observed for pregnenolone, which was over 10-fold greater. Both forms of expressed protein can catalyze the reduction of dihydrotestosterone to 5 alpha-androstanediol in the presence of the cofactor NADH, but with considerably higher Km values (5.5 microM for form I and 6.8 microM for form III). The observed maximum velocity of form I was much higher for all substrates examined. RNase protection and immunoblot analysis of expressed 3 beta HSD I and III indicate that the difference in maximum velocity reflect differences in the steady state levels of mRNA and amounts of protein. In addition, the expressed 3 beta HSD III protein analyzed by Western blot has a lower mobility than the 3 beta HSD I protein, both similar in mol wt to the 3 beta HSD proteins detected in mouse liver and adrenal glands, respectively. These data demonstrate that an isoform of 3 beta HSD expressed in liver and kidney has the capacity to convert delta 5-3 beta-hydroxysteroids to delta 4-3-ketosteroids. The data suggest that a homologous human 3 beta HSD isoform could play an important role in cases of genetic deficiency of the gonadal and adrenal isoform.
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PMID:Enzyme characteristics of two distinct forms of mouse 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase complementary deoxyribonucleic acids expressed in COS-1 cells. 847 48

The biosynthesis of steroid hormones in the gonads and adrenal glands requires the activities of the enzyme 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta HSD) which catalyzes the NAD(+)-dependent dehydrogenation and subsequent delta 5-->delta 4 isomerization of delta 5-3 beta-hydroxysteroids to delta 4-3-ketosteroids. The mouse expresses four isoforms of 3 beta HSD. 3 beta HSD I is expressed in gonads and adrenal glands and appears to be the major steroidogenic form, 3 beta HSDs II and III are expressed in both liver and kidneys, and 3 beta HSD IV has been detected only in kidneys. To determine the genetic relationship between the 3 beta HSD isoforms, we have mapped the chromosomal locations of the four genes by linkage analysis using gene-specific probes derived from the 3' untranslated regions of 3 beta HSD cDNA clones. The four 3 beta HSD structural genes (Hsd3b) are closely linked within a segment of chromosome 3 that is conserved on human chromosome 1. The order of markers on Chr 3 surrounding Hsd3b is: centromere-Gba-(4.4 +/- 2.2)-Hsd3b-(3.3 +/- 1.9)-Tshb-(6.7 +/- 2.7)-Amy-1.
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PMID:The genes encoding gonadal and nongonadal forms of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase are closely linked on mouse chromosome 3. 848 61

We compare testosterone (T) metabolism in primary cultures of epithelial cells and fibroblasts separated from benign prostate hypertrophy (BPH) and prostate cancer tissues. In all cultures, androstenedione (delta 4) formed by oxidation of T by 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) represented 80% of the metabolites recovered. The amounts of 5 alpha-dihydrotestosterone (DHT), formed by reduction of T by 5 alpha-reductase (5 alpha-R), were small: 5 and 2% (BPH) and 8 and 15% (adenocarcinoma) for epithelial cells and fibroblasts, respectively. Northern blot analysis of total RNA from epithelial cells (BPH or adenocarcinoma) attributed the reductive activity to the 5 alpha-reductase type 1 isozyme and oxidative activity to the 17 beta-HSD type 2. In cancer fibroblasts, only little 17 beta-HSD type 2 mRNA was detected. The 5 alpha-reductase inhibitors, 4-MA (17 beta-(N,N-diethyl)carbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one) and finasteride, inhibited DHT formation with a preferential action of 4-MA on epithelial cells (BPH or adenocarcinoma) and of finasteride on fibroblasts from adenocarcinoma. Neither inhibitor acted on delta 4 formation. On the other hand, the lipido-sterol extract of Serenoa repens (LSESr, Permixon) inhibited the formation of all the T metabolites studied [IC50 S = 40 and 200 micrograms/ml (BPH) and 90 and 70 micrograms/ml (adenocarcinoma) in epithelial cells and fibroblasts, respectively]. These results have important therapeutic implications when selecting appropriate treatment options for BPH.
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PMID:Testosterone metabolism in primary cultures of human prostate epithelial cells and fibroblasts. 854 Dec 34

A steroidogenic pathway from cholesterol to aldosterone was reconstituted in liposome membranes using cytochromes P-450scc, P-450C21 and P-450(11) beta, and 3 beta-hydroxysteroid dehydrogenase/ delta 5-delta 4 isomerase (3 beta HSD/I) with their electron transfer systems. All of the enzymes were purified from bovine adrenocortical mitochondria and microsomes. The cholesterol metabolism in the liposomal reconstituted system was compared with that in the combined organella system composed of bovine adrenocortical mitochondria and microsomes, where the activity of P-450(17) alpha,lyase was inhibited by bifonazole. The metabolic activities in these two systems were similar except for aldosterone production. Aldosterone was produced in the liposomal system but not in the combined organella system. 4-fold increase in the amount of P-450scc in the liposomal system enhanced the activity of 3 beta HSD/I, P-450C21 and 11 beta-hydroxylase of P-450(11) beta but decreased 18-hydroxycorticosterone and aldosterone production by P-450(11) beta, supporting our previous findings describing the regulation mechanism of aldosterone synthesis (Kominami, S., Harada, D. and Takemori, S. (1994) Biochim. Biophys. Acta 1192, 234). It was demonstrated using the liposomal reconstituted system that the increase in the amount of one enzyme did not only increase the metabolizing activity of that enzyme but also affect other enzyme in various ways.
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PMID:Reconstitution of the steroidogenic pathway from cholesterol to aldosterone in liposome membranes. 866 29

Benign meningioma tumors possess significant levels of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity. Two different 17 beta-HSDs were discovered in human placenta: one highly estrogen specific and using NADP+/NADPH as cofactors (type-1 17 beta-HSD), and a second one that utilizes both androgens and estrogens as substrates with NAD+/NADH (type-2 17 beta-HSD). Recently, two further human 17 beta-HSDs were isolated. A testis-specific 17 beta-HSD (type-3 17 beta-HSD) favors the reduction of delta 4-androstenedione to testosterone, and a ubiquitously expressed type-4 17 beta-HSD preferentially catalyzes the oxidation of estradiol and delta 5-androstenediol. In this study we characterize the expression levels of different types of 17 beta-HSD in a wide series of tumors. Using the Northern blotting method we show that type-1, -3, and -4 17 beta-HSDs are not detectable in meningiomas. In contrast, the type-2 17 beta-HSD RNA is present in 6 of 17 meningiomas and its abundance is directly correlated with estrogenic 17 beta-HSD activity (r2 = 0.74). The presence of type-2 17 beta-HSD is also demonstrated by in situ hybridization. RT-PCR and Western blots show that type-4 17 beta-HSD is also present, though at much lower levels. The progesterone receptor level, the epidermal growth factor receptor level, and the age of the patients are not correlated with the estrogenic 17 beta-HSD activity or type-2 17 beta-HSD mRNA expression level.
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PMID:17 beta-Hydroxysteroid dehydrogenase activity correlates with the type-2 17 beta-hydroxysteroid dehydrogenase mRNA abundance in human meningioma tumors. 881 69

Classic 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) deficiency congenital adrenal hyperplasia (CAH) results from a mutation in the type II 3 beta HSD gene encoding adrenal and gonadal 3 beta HSD. We investigated the type II and type I 3 beta HSD gene sequences in 15 infants and children with premature pubarche (PP; mean/range of age at PP, 4/0.08-9 yr) and elevated ACTH-stimulated delta 5 precursor steroid levels. Compared to Tanner I control subjects of similar age, ACTH-stimulated hormonal levels were at 2.3-10.7 SD for 17-hydroxypregnenolone (delta 5-17P) in all PP subjects, at 2.2-17 SD for dehydroepi-androsterone (DHEA) and 2.4-5.6 SD for the delta 5-17P/cortisol (F) ratio in all PP subjects except 1 infant, and at 2.3-10 SD for the DHEA/ androstenedione (delta 5-A) ratio in 8 PP subjects. Compared to Tanner II normal children, the hormonal levels were at 3-8 SD for delta 5-17P in all 13 PP children, at 2.3-4.7 SD for the delta 5-17P/F ratio in 6 PP children, and at 2.3-6.5 SD for DHEA and 3.5-9 SD for the DHEA/delta 4-A ratio in 7 PP children. Type II 3 beta HSD gene sequences, including regions of a putative promoter, all exons (I, II, III, and IV), and exon-intron boundaries, were normal in all subjects. Sequences of the type I 3 beta HSD gene encoding extraadrenal and extragonadal 3 beta HSD were normal in the 6 patients tested. The ACTH-stimulated delta 5-17P levels and delta 5-17P/F ratios in the PP children without type II 3 beta HSD gene mutation were exceedingly lower than the respective reported hormonal data for children with 3 beta HSD deficiency CAH with proven type II 3 beta HSD gene mutation. The ACTH-stimulated DHEA levels and DHEA/delta 4-A ratios were not exceedingly different between the children with and without type II 3 beta HSD gene mutation. These findings suggest that the degree of ACTH-stimulated delta 5 precursor steroid abnormality, such as delta 5-17P levels up to 10 SD above the normal mean level found in our PP patients, is not caused by a mild variant of 3 beta HSD deficiency CAH resulting from type II or type I 3 beta HSD gene mutation. The hormonal criterion for ACTH-stimulated delta 5-17P levels in patients with mild variant 3 beta HSD deficiency, therefore, is predicted to be higher than 10 SD above the normal mean value.
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PMID:Studies of 3 beta-hydroxysteroid dehydrogenase genes in infants and children manifesting premature pubarche and increased adrenocorticotropin-stimulated delta 5-steroid levels. 892 44

Previous studies have shown that the ability of Brown Norway rat Leydig cells to produce testosterone declines significantly with age. To address the possible mechanism(s) by which aging Leydig cells lose steroidogenic function, we determined the effect of age on the steady-state levels of the mRNAs for the steroidogenic enzymes P450 cholesterol side-chain cleavage (P450scc), delta 5-3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD), and 17 alpha-hydroxylase/C17-20 lyase (P450(17) alpha), and on the levels of immunoreactive steroidogenic enzyme proteins and enzyme activities. Northern blot analysis revealed that the levels of P450scc and P450(17) alpha mRNAs in Leydig cells isolated from the testes of aged (22-month-old) Brown Norway rats were reduced from their levels in young (4-month-old) rats, but that 3 beta-HSD mRNA was not reduced. Western blot analysis, however, revealed that cellular levels of each of the P450scc, P450(17) alpha, and 3 beta-HSD proteins were reduced with aging. The activities of the steroidogenic enzymes, assessed by incubating Leydig cells in culture with substrate and then summing all steroidogenic reaction products through testosterone, similarly revealed that P450scc, 3 beta-HSD, P450(17) alpha, and additionally 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), were all reduced with aging. We conclude that age-related loss of steroidogenic function results at least in part from reductions in the levels and activities of each of the steroidogenic enzymes responsible for converting cholesterol to testosterone, and not by differential regulation of these enzymes.
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PMID:Are Leydig cell steroidogenic enzymes differentially regulated with aging? 895 94

There is growing evidence that various isoforms of 17 beta-hydroxysteroid dehydrogenase (17-HSD) are regulated at the level of catalysis in intact cells. A number of investigators have proposed that the NAD(P)/NAD(P)H ratio may control the direction of reaction. In a previous study, we obtained evidence that A431 cells, derived from an epidermoid carcinoma of the vulva, are enriched in 17-HSD type 2, a membrane-bound isoform reactive with C18 and C19 17 beta-hydroxysteroids and 17-ketosteroids. The present investigation was undertaken to confirm the presence of 17-HSD type 2 in A431 cells and to assess intracellular regulation of 17-HSD at the level of catalysis by comparing the activity of homogenates and microsomes with that of cell monolayers. Northern blot analysis confirmed the presence of 17-HSD type 2 mRNA. Exposure of cells to epidermal growth factor resulted in an increase in type 2 mRNA and, for microsomes, increases in maximum velocity (Vmax) with no change in Michaelis constant (Km) for testosterone and androstenedione, resulting in equivalent increases in the Vmax/Km ratio consistent with the presence of a single enzyme. Initial velocity data and inhibition patterns were consistent with a highly ordered reaction sequence in vitro in which testosterone and androstenedione bind only to either an enzyme-NAD or an enzyme-NADH complex respectively. Microsomal dehydrogenase activity with testosterone was 2- to 3-fold higher than reductase activity with androstenedione. In contrast, although cell monolayers rapidly converted testosterone to androstenedione, reductase activity with androstenedione or dehydroepiandrosterone (DHEA) was barely detectable. lactate but not glucose, pyruvate or isocitrate stimulated the conversion of androstenedione to testosterone by monolayers, suggesting that cytoplasmic NADH may be the cofactor for 17-HSD type 2 reductase activity with androstenedione. However, exposure to lactate did not result in a significant change in the NAD/NADH ratio of cell monolayers. It appears that within A431 cells 17-HSD type 2 is regulated at the level of catalysis to function almost exclusively as a dehydrogenase. These findings give further support to the concept that 17-HSD type 2 functions in vivo principally as a dehydrogenase and that its role as a reductase in testosterone formation by either the delta 4 or delta 5 pathway is limited.
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PMID:Intracellular regulation of 17 beta-hydroxysteroid dehydrogenase type 2 catalytic activity in A431 cells. 920


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