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)

Danazol (4 mg/day/animal) and oestradiol-17 beta (100 microgram/day/animal) were administered subcutaneously for 22 and 15 days respectively. The testis and epididymis were histochemically analysed for steroid dehydrogenases, NADH-diaphorase, glucose 6-phosphate dehydrogenase activity and lipids. Both steroids significantly reduced the weights of the testis and other accessory reproductive organs. The activities of delta 5-3 beta- and 17 beta-HSD were markedly reduced in the seminiferous epithelium and interstitial cells of the testis. Sudanophilic lipids accumulated in the seminiferous tubules and the interstitium. Oestradiol generally had a greater effect than did danazol, but both probably affect the testicular function by inhibiting steroidogenesis.
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PMID:A histochemical study of the effect of danazol and oestradiol-17 beta on steroidogenic activity in testis and epididymis of the gerbil, Tatera indica. 693 36

5'-[p-(Fluorosulfonyl)benzoyl]adenosine (FSA) was used to affinity-label the NADH binding region of 3 alpha, 20 beta-hydroxysteroid dehydrogenase (3 alpha, 20 beta-HSD) to further test our hypothesis [Sweet, F., & Samant, B. R. (1980) Biochemistry 19, 978-986] that 3 alpha and 20 beta activities occur at the same active site. Incubation of 3 alpha, 20 beta-HSD (0.45 microM) with FSA (125 microM) at pH 7.0 and 0 degrees C caused simultaneous loss of 3 alpha and 20 beta activities by a first-order kinetic process, with t1/2 = 300 min for both activities. Dinucleotides and adenosine mononucleotides which acted as competitive inhibitors protected 3 alpha, 20 beta-HSD against inactivation by FSA in a concentration-dependent manner, in the order reduced nicotinamide dinucleotide phosphate greater than oxidized nicotinamide dinucleotide phosphate greater than adenosine diphosphate-ribose greater than adenosine diphosphate greater than adenosine monophosphate (AMP) greater than adenosine. Oxidized and reduced nicotinamide mononucleotides (NMH and NMNH) and steroid substrates did not protect 3 alpha, 20 beta-HSD against affinity labeling by FSA. Although NMN was not a competitive inhibitor of 3 alpha, 20 beta-HSD, NMN with AMP and also AMP with NMNH produced positive cooperativity for competitive inhibition of 3 alpha, 20 beta-HSD. The results from FSA affinity labeling of the cofactor region confirm that both 3 alpha and 20 beta activities share the same active site of 3 alpha, 20 beta-HSD and suggest a model of cofactor binding and promotion of enzyme activity. The adenosine 5'-phosphate component anchors the NAD or NADH to an adenosine domain in the cofactor binding region. The nicotinamide nucleotide component then carries out the hydrogen-transfer reaction at a neighboring domain near the steroid binding region.
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PMID:Nicotinamide adenine dinucleotide binding and promotion of enzyme activity: model based on affinity labeling of 3 alpha, 20 beta-hydroxysteroid dehydrogenase with a nucleoside. 694 73

Gonadectomy of male rats led to a threefold increase of 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSDH) activity in pituitary homogenates that could be completely reversed by chronic administration of estradiol or 5 alpha-dihydrotestosterone (DHT). 3 alpha-HSDH was found to be distributed mainly between the 10,000 g and 100,000 g sediments from whole homogenates. The microsomal enzyme activity showed a substantial specificity for NADH whereas the cytosolic enzyme (100,000 g supernatant) demonstrated a slight preference for NADPH. The changes in Vmax found in homogenates following gonadectomy and gonadal steroid administration reflected changes in NADH-linked activity of the microsomal, but not the cytosolic enzyme. Estradiol-induced suppression of NADH-linked 3 alpha-HSDH activity in pituitary homogenates from gonadectomized rats of either sex was accompanied by a similar suppression of NADPH-linked 5 alpha-reductase activity and a marked decrease of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release. In the ovariectomized rat chronic administration of nonsteroidal antiestrogens had strong estrogenic effects on 3 alpha-HSDH activity and LH release, but not on 5 alpha-reductase activity and FSH release. In the gonadectomized male rat, which was much less sensitive to intrinsic estrogenicity of the antiestrogens tested, nafoxidine completely blocked estradiol-induced suppression of 5 alpha-reductase activity and FSH release and partially antagonized suppression of LH release. The trans-isomeric, substituted triphenylethylenes, tamoxifen, and enclomiphene, as well as nitromifene (mixture of trans and cis isomers) were able partially to counteract estradiol-induced suppression of 5 alpha-reductase, but not 3 alpha-HSDH activity. It is concluded that estradiol action on pituitary 5 alpha-reductase, but not 3 alpha-HSDH activity, involves an estrogen receptor mechanism.
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PMID:Subcellular distribution of 3 alpha-hydroxysteroid dehydrogenase and antiestrogen action on androgen-metabolizing enzymes in rat pituitary gland. 695 28

The 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSDH) is a key enzyme in human fetal and maternal progesterone metabolism. In this paper, the cytoplasmic 20 alpha-HSDH of human term placenta is partially characterized in vitro. A 14-fold concentration of the 20 alpha-HSDH was prepared by ultracentrifugation and ammonium sulfate precipitation. The apparent Km values for the substrates progesterone (Km: 4.8 x 10(-5) M) and 20 alpha-DHP (Km: 6.2 x 10(-5) M) and for the cofactors NADPH (Km: 1.9 x 10(-4)) and NADH (Km: 2.6 x 10(-4)) were determined. The temperature optimum for the oxidation of 20 alpha-DHP is 40--50 degrees C. The pH optimum for the reduction of progesterone was found to be pH 6.2 and for the oxidation of 20 alpha-DHP pH 6.5. The addition of glycerol (3 M) to the incubation medium inhibited the conversion rate of 20 alpha-HSDH by 70%. No influence of EDTA could be found. Various bivalent metal ions (1--100 mM) showed a dose-dependent inhibition of 20 alpha-HSDH; a complete inhibition was achieved at 100 mM: Cu2+, Zn2+, Cd2+, Fe2+ and Ni2+.
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PMID:Partial characterization of the cytoplasmic 20 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.149) of the human placenta at term. 695 67

Meningioma benign tumors possess significant levels of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity. Two different 17 beta-HSDs have been cloned and characterized. The cytosolic 17 beta-HSD I which exclusively catalyzes the interconversion of 17 beta-estradiol (E2) and estrone (E1) preferentially uses NADP+ and NADPH as cofactors. In contrast, the mitochondrial-microsomal 17 beta-HSD II catalyzes both the estrogenic as well as the androgenic substrates of the 17 beta-HSD and uses NAD+ and NADH as cofactors. We demonstrated here that the 17 beta-HSD activity in meningioma tissue homogenate is both estrogenic and androgenic with Km values of 2.4, 0.4, 14.7, and 2.0 microM for E2, E1, testosterone (T), and delta 4-androstenedione (delta 4), respectively. NAD(+)-NADH is almost exclusively used as cofactor in this tissue. Moreover, fractionation of meningioma tissue revealed that most of the 17 beta-HSD activity is present in the mitochondrial-microsomal fraction. Although Northern blot analysis on meningiomas with a specific probe for human 17 beta-HSD I showed no band, the specific cDNA probe of human 17 beta-HSD II hybridized at the expected size of 1.5 kb, which was also present in placenta. On four different meningioma tumors, we were able to correlate 17 beta-HSD II mRNA expression to high levels of 17 beta-HSD activity. Taken together, the present data suggest that the meningioma 17 beta-HSD could be the 17 beta-HSD II.
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PMID:Characterization of 17 beta-hydroxysteroid dehydrogenase activity and mRNA abundance in human meningioma tumors. 782 86

Estradiol 17 beta-hydroxysteroid dehydrogenase (17 beta HSD) mediates the interconversion of estrone and estradiol in endocrine-responsive tissues such as the breast. The control of 17 beta HSD expression by all-trans-retinoic acid (RA) in T47D breast cancer cells was examined using a specific 17 beta HSD complementary DNA probe. Two main 17 beta HSD messenger RNA (mRNA) transcripts of 2.2 and 1.3 kilobases (kb) were detected, of which only the 1.3-kb mRNA was regulated. RA increased expression of the 17 beta HSD 1.3-kb mRNA in a dose- and time-dependent manner, and the increased expression of this mRNA by RA was inhibited by a 10-fold excess of a RA antagonist Ro 41-5253. Insulin-like-growth factor-I, interleukin-1, and estradiol, previously shown to increase 17 beta HSD activity in breast cancer cells, had little effect on 17 beta HSD gene expression. To relate the effect of increased 17 beta HSD 1.3-kb mRNA expression to 17 beta HSD activity, the conversion of estrone to estradiol (reductive) and that of estradiol to estrone (oxidative) were measured in intact T47D cell monolayers. Whereas RA increased 17 beta HSD reductive activity, it had no effect on oxidative activity. The addition of excess NAD increased 17 beta HSD oxidative activity in control and RA-treated cells, but the addition of NADH had no effect on 17 beta HSD reductive activity. These results suggest that the increased expression of the 17 beta HSD 1.3-kb mRNA induced by RA is associated with an increase in 17 beta HSD reductive activity, but that endogenous cofactor levels may determine the direction in which this enzyme acts in T47D cells.
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PMID:Regulation of estradiol 17 beta-hydroxysteroid dehydrogenase expression and activity by retinoic acid in T47D breast cancer cells. 801 76

Incubation of whole LNCaP cells in suspension with tritium labeled cortisol revealed two major and one minor radioactive product. Of the major products, one migrated with an Rf value identical to cortisol (Kendall's compound "F"), and the second migrated with an Rf value similar to nonradioactive cortisone (Kendall's compound "E"); the third minor product comigrated with 21-acetylated cortisol. The conversion of cortisol to cortisone was linear with respect to cell number, and conversion reached a plateau after 120 min of incubation at 37 degrees C. One half of the cortisol was converted to cortisone within 2 h of incubation at 37 degrees C. This conversion was nicotine amide dinucleotide (NAD) dependent. Low levels of transcription activation by cortisol were documented in LNCaP cells transfected with glucocorticoid and androgen responsive mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase chimeric gene (MMTV-CAT). Hormone binding assay and transactivation analysis revealed the presence of a functional mineralocorticoid receptor in LNCaP cells. Treatment of transfectants with F in the presence of carbenoxolone, a potent inhibitor of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), resulted in a two orders of magnitude increase in measurable CAT activity. The addition of the reduced form of nicotine amide dinucleotide (NADH) in the presence of 10(-7) M E stimulated measurable CAT activity in LNCaP cells. In conferring aldosterone specificity in mineralocorticoid target tissues, 11 beta-HSD may have an important role as "gate keeper" in allowing a specific androgen response in hormone responsive LNCaP prostate cancer cells.
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PMID:11 beta-Hydroxysteroid dehydrogenase and tissue specificity of androgen action in human prostate cancer cell LNCaP. 803 14

The overexpression and purification of recombinant rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase (3 alpha-HSD; EC 1.1.1.50) in Escherichia coli are described. The properties of the homogeneous recombinant 3 alpha-HSD (r3 alpha-HSD) confirm that a single polypeptide can function as a HSD, as a dihydrodiol dehydrogenase, and as an aromatic aldehyde, ketone, and quinone reductase. Cys-170, Cys-242, and Cys-217, implicated by bromoacetoxysteroid affinity-labeling agents as points of contact for the C-3, C-11, and C-17 positions of steroid ligands, were mutated to alanines. Unexpectedly, the homogeneous C170A and C242A mutants were kinetically similar to wild-type r3 alpha-HSD. By contrast, the C217A mutant gave Km values that were 4-fold higher for androstanedione and 2-fold higher for NADH. Inspection of the recently solved crystal structure of rat liver 3 alpha-HSD (Hoog, S. S., Pawlowski, J. E., Alzari, P. M., Penning, T. M., and Lewis, M. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 2517-2521) places Cys-170 and Cys-242 on the periphery of an alpha/beta-barrel so that they cannot be involved in catalysis of steroid recognition. This demonstrates that bromoacetoxysteroid affinity-labeling agents may provide misleading information regarding the topography of steroid hormone binding sites. When NADPH was modeled into the crystal structure of 3 alpha-HSD, Tyr-55 was implicated as the general acid, since it is in close proximity to the C-4 position of the nicotinamide ring and could polarize the substrate carbonyl. In support of this model, the purified Y55F mutant was found to be catalytically inactive, but still formed an E-NADPH complex (measured by fluorescence titration) and an E-NADH-testosterone complex (measured by equilibrium dialysis). The ability of the Y55F mutant to form binary and ternary complexes, but not aid in hydride transfer, is consistent with Tyr-55 acting as the general acid. 3 alpha-HSD is a member of the aldo-keto reductase superfamily, and Tyr-55 is invariant in members of this family where it may perform a similar function. Tyr-205 is present in a pentapeptide sequence that is conserved in HSDs that belong to the short-chain alcohol dehydrogenase family and has been implicated as the general acid within these enzymes. The Y205F mutant was found to be kinetically similar to wild-type r3 alpha-HSD.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Overexpression and mutagenesis of the cDNA for rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase. Role of cysteines and tyrosines in catalysis. 817 84

11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) catalyzes the conversion of active cortisol to inactive cortisone, and regulates the access of cortisol to both the mineralocorticoid and glucocorticoid receptors. Two isoforms of 11 beta-HSD have been described, the cloned "type 1" NADP(H)-dependent dehydrogenase/oxo-reductase and a high affinity NAD-dependent dehydrogenase (type 2). In the fetus, 11 beta-HSD activity may serve to protect developing tissues from cortisol excess or may modulate the permissive actions of glucocorticoids. We have studied 11 beta-HSD activity and mRNA levels in human mid-gestational fetal tissues. Tissue homogenates were incubated with either 0.1 mumol/L cortisol and 400 mumol/L NAD, 2.5 mumol/L cortisol and 400 mumol/L NADP, or 0.1 mumol/L cortisone wither either 400 mumol/L NADPH or NADH. No activity (< 2.5% conversion) was observed in fetal tissues using either cortisone or 2.5 mumol/L cortisol as a substrate. 11-oxo-reductase activity was observed in maternally-derived decidua. In keeping with these activity studies, northern blot analysis of fetal tissue RNA and PCR-reverse transcriptase of type 1 11 beta-HSD mRNA indicated 11 beta-HSD mRNA in decidua, but failed to detect any type 1 11 beta-HSD mRNA transcripts in fetal tissues. In contrast when 0.1 mumol/L cortisol was used as a substrate in the presence of NAD, 11 beta-HSD activity was ubiquitous with highest levels seen in the kidney (131 +/- 16 (SE) pmoles cortisone formed/h/mg.protein) > lung > gonad > liver > colon. 11 beta-HSD activity in fetal tissues is mediated by the type 2, high affinity, isoform. The widespread distribution of this novel isoform suggests that it may play an important role in fetal development. Type 1 11 beta-HSD mRNA and activity are absent in mid-gestational fetal tissues, but present in maternally-derived decidua, suggesting that its ontogeny is a late-gestational of post-natal event.
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PMID:Type 2 11 beta-hydroxysteroid dehydrogenase in human fetal tissues. 820 Sep 59

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) is considered to confer mineralocorticoid specificity on the non-selective Type I adrenocorticoid receptor by converting active 11-hydroxyglucocorticoids to receptor-inactive 11-oxo metabolites, in mineralocorticoid target tissues like the kidney. However, 11 beta-HSD is also present in the liver, where it may regulate steroid exposure to the glucocorticoid Type II receptor. Because of the much higher activities compared to that in kidney, liver 11 beta-HSD possibly has additional functions besides the metabolism of glucocorticoids. In the present investigation we have isolated 11 beta-HSD from mouse liver microsomes and demonstrate that the homogeneously purified enzyme is also capable of catalyzing the reductive metabolism of xenobiotic carbonyl compounds such as metyrapone, p-nitroacetophenone and p-nitrobenzaldehyde. Enzyme kinetic studies revealed that, in addition to NADP+, mouse liver 11 beta-HSD also accepts NAD+ as cosubstrate for glucocorticoid 11 beta-dehydrogenation. NADH as cosubstrate for 11-oxoreduction plays only a minor role compared to that with NADPH, a fact which is also true for xenobiotic carbonyl reduction. Inhibition experiments revealed strong sensitivity of xenobiotic carbonyl reduction to glucocorticoids. The competitive nature of this inhibition suggests that both glucocorticoids and xenobiotic carbonyl substances bind to the same catalytically active site of 11 beta-HSD. High enzyme activities were also found in microsomal fractions of the ovary and adrenal gland but, although expressing considerable glucocorticoid 11-dehydrogenation activity (one third that of liver), almost no carbonyl reduction was detectable in kidney microsomes. Immunoblot analysis with polyclonal antibodies directed against the liver 11 beta-HSD did not yield an immunological crossreaction in the same tissues. In conclusion, corresponding to the cytosolic aldo-keto reductases, microsomal 11 beta-HSD of liver may be considered to play a role in the phase I biotransformation of pharmacologically relevant carbonyl substances as well as protecting organisms against toxic carbonyl compounds by converting them to less lipophilic and more soluble and conjugatable metabolites. Discrepancies in bioactivity together with the lack of response to anti-liver 11 beta-HSD antibodies strongly indicate the existence of distinct forms of 11 beta-HSD to be present in kidney, adrenal gland and ovary. The ability of xenobiotic carbonyl reduction might be another distinguishing feature among the various 11 beta-HSD isozymes.
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PMID:11 beta-hydroxysteroid dehydrogenase mediates reductive metabolism of xenobiotic carbonyl compounds. 820 97


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