Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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In earlier studies, two distinct molecules, 20 alpha-HSD-I and 20 alpha-HSD-II, responsible for 20 alpha-HSD activity of pig adrenal cytosol were purified to homogeneity and characterized [S. Nakajin et al., J. Steroid Biochem. 33 (1989) 1181-1189]. We report here that the purified 20 alpha-HSD-I, which mainly catalyzes the reduction of 17 alpha-hydroxyprogesterone to 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, catalyzes 3 alpha-hydroxysteroid oxidoreductase activity for 5 alpha (or 5 beta)-androstanes (C19), 5 alpha (or 5 beta)-pregnanes (C21) in the presence of NADPH as the preferred cofactor. The purified enzyme has a preference for the 5 alpha (or 5 beta)-androstane substrates rather than 5 alpha (or 5 beta)-pregnane substrates, and the 5 beta-isomers rather than 5 alpha-isomers, respectively. Kinetic constants in the reduction for 5 alpha-androstanedione (Km; 3.3 microM, Vmax; 69.7 nmol/min/mg) and 5 beta-androstanedione (Km; 7.7 microM, Vmax; 135.7 nmol/min/mg) were demonstrated for comparison with those for 17 alpha-hydroxyprogesterone (Km; 26.2 microM, Vmax; 1.3 nmol/min/mg) which is a substrate for 20 alpha-HSD activity. Regarding oxidation, the apparent Km and Vmax values for 3 alpha-hydroxy-5 alpha-androstan-17-one were 1.7 microM and 43.2 nmol/min/mg, and 1.2 microM and 32.1 nmol/min/mg for 3 alpha-hydroxy-5 beta-androstan-17-one, respectively. 20 alpha-HSD activity in the reduction of 17 alpha-hydroxyprogesterone catalyzed by the purified enzyme was inhibited competitively by addition of 5 alpha-DHT with a Ki value of 2.0 microM. Furthermore, 17 alpha-hydroxyprogesterone inhibited competitively 3 alpha-HSD activity with a Ki value of 150 microM.
J Steroid Biochem Mol Biol 1992 Feb
PMID:3 alpha-hydroxysteroid dehydrogenase activity catalyzed by purified pig adrenal 20 alpha-hydroxysteroid dehydrogenase. 154 86

5 alpha-Dihydrotestosterone 3 alpha(beta)-hydroxysteroid dehydrogenase [3 alpha(beta)-HSDH] [EC 1.1.1.50/EC 1.1.1.51] which catalyses the conversion of 5 alpha-dihydrotestosterone (5 alpha-DHT) to both 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol was purified to an apparent homogeneous state using cytosol of three human hyperplastic prostates by a 4-step purification procedure. After each purification step 3 alpha-HSDH activity was coincident with 3 beta-HSDH activity. On average, specific 3 alpha-HSDH activity was enriched 856-fold, specific 3 beta-HSDH activity 749-fold compared to human prostatic cytosol using anion exchange, hydrophobic interaction, gel filtration and affinity chromatography. Examination of the purified enzyme by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS) revealed a single protein band with silver staining. The molecular weight of the enzyme was estimated as 33 kDa by SDS-polyacrylamide gel electrophoresis and as 28 kDa by Sephacryl S-200 gel filtration indicating that the native 3 alpha(beta)-HSDH is a monomer. In the presence of the preferred co-factor, NADPH, the purified enzyme had a mean apparent Km for 5 alpha-DHT of 3.9 microM and a Vmax of 93.3 nmol (mg protein)-1 h-1 with regard to 3 alpha-HSDH activity, and a Km of 6.3 microM and a Vmax of 20.6 nmol (mg protein)-1 h-1 with regard to 3 beta-HSDH activity.
J Steroid Biochem Mol Biol 1992 May
PMID:Purification and properties of the 5 alpha-dihydrotestosterone 3 alpha(beta)-hydroxysteroid dehydrogenase from human prostatic cytosol. 160 44

The mechanism of stimulation of 17 beta-estradiol (E2) formation from estrone (E1) by 5 alpha-dihydrotestosterone (5 alpha-DHT) in placental villi was investigated by examining; (1) if dehydroepiandrosterone (DHA) was stimulatory, (2) if NAD(P)H-generating, non-steroidal substrates stimulated E2 formation, (3) the subcellular localization of the effect, (4) if NAD(P) or NAD(P)H was required and (5) rates of 5 alpha-DHT oxidation by villi and microsomes. Although 5 alpha-DHT and DHA both inhibited the E2 to E1 reaction in villi and microsomes, only 5 alpha-DHT stimulated the conversion of E1 to E2. Glucose and lactate were slightly stimulatory when compared with 5 alpha-DHT. Stimulation of E2 formation was observed with microsomes but not with cytosol, and NAD or NADP was required. The results indicate that neither inhibition of the back reaction, E2 to E1, nor NADH or NADPH formation via the 3 beta-hydroxysteroid dehydrogenase/5-ene-3-ketosteroid isomerase reaction can account for the stimulation. It is proposed that the mechanism of stimulation involves one or more forms of membrane-bound 17 beta-hydroxysteroid oxidoreductase with NADH or NADPH formed as a product of 5 alpha-DHT oxidation being used as the cofactor for E1 reduction. This may involve a direct transfer of reduced pyridine nucleotide between enzyme molecules without equilibration with intracellular coenzyme pools.
J Steroid Biochem Mol Biol 1991 Nov
PMID:Regulation of human placental 17 beta-hydroxysteroid oxidoreductase: mechanism of stimulation of 17 beta-estradiol formation from estrone by 5 alpha-dihydrotestosterone in homogenates and villi in vitro. 165 69

Human hyperplastic prostate tissue was homogenised in high ionic strength buffer and the post nuclear homogenate was incubated with 0.8% octyl glucoside and bovine brain lipids. Dialysis of the resulting liposome suspension yielded a preparation in which 5 alpha-reductase was active and stable for at least three weeks and showed an increase in specific activity (Vmax +/- SD = 48.9 +/- 7.4 pmol DHT/mg protein/ml) over that of the starting homogenate (Vmax +/- SD = 5.6 +/- 1.5 pmol DHT/mg protein/min) of 8.7 times.
J Steroid Biochem Mol Biol 1991 Jan
PMID:Partial purification of human prostatic 5 alpha-reductase (3-oxo-5 alpha-steroid:NADP+ 4-ene-oxido-reductase; EC 1.3.1.22) in a stable and active form. 170 42

Many central actions of testosterone (T) require the transformation of T into several metabolites including 5 alpha-dihydrotestosterone (5 alpha-DHT) and estradiol (E2). In birds as in mammals, 5 alpha-DHT and E2, alone or in combination, mimic most behavioral effects of T. The avian brain is, in addition, able to transform T into 5 beta-DHT, a metabolite which seems to be devoid of any behavioral or physiological effects, at least in the context of reproduction. By in vitro product-formation assays, we have analyzed the distribution, sex differences and regulation by steroids of the 3 main T metabolizing enzymes (aromatase, 5 alpha- and 5 beta-reductases) in the brain of the Japanese quail (Coturnix c. japonica) and the zebra finch (Taeniopygia guttata castanotis). In the hypothalamus of quail and finches, aromatase activity is higher in males than in females. It is also decreased by castration and increased by T. The activity of the 5 alpha-reductase is not sexually differentiated nor controlled by T. The 5 beta-reductase activity is often higher in females than in males but this difference disappears in gonadectomized birds and no clear effect of T can be observed at this level. The zebra finch brain also contains a number of steroid-sensitive telencephalic nuclei [e.g. hyperstriatum ventrale, pars caudale (HVc) and robustus archistriatalis (RA)] which play a key role in the control of vocalizations. These nuclei also contain T-metabolizing enzymes but the regulation of their activity is substantially different from what has been observed in the hypothalamus. Aromatase activity is for example higher in females than in males in HVc and RA and the enzyme in these nuclei is not affected by castration nor T treatment. In these nuclei, the 5 alpha-reductase activity is higher in males than in females and the reverse is true for the 5 beta-reductase. These sex differences in activity are not sensitive to gonadectomy and T treatment and might therefore be organized by neonatal steroids. We have been recently able to localize aromatase-immunoreactive (AR-ir) neurons by ICC in the brain of the quail and zebra finch. Positive cells are found in the preoptic area, ventromedial and tuberal hypothalamus. AR-ir material is found in the perikarya of cells and fills the entire cellular processes including axons. At the electron microscope level, immunoreactive material can clearly be observed in the synaptic boutons. This observation raises questions concerning the mode of action of estrogens produced by central aromatization of T.
J Steroid Biochem Mol Biol 1991
PMID:Testosterone metabolism in the avian hypothalamus. 195 58

Liver and kidney from fetal monkeys (day 125 of gestation) were fractionated into low speed pellets, microsomal and cytosolic fractions. Liver cytosols converted as much testosterone (T) to 5 beta-androstane-3 alpha,17 beta-diol (5 beta-diol) at 0 degrees C as at 4 degrees-45 degrees C without exogenous cofactors. The principal product formed from 5 alpha-dihydrotestosterone (5 alpha-DHT) was 5 alpha-diol. A 1000-fold molar excess of radioinert 5 beta- or 5 alpha-DHT inhibited 5 beta-diol formation from [3H]T by cytosols and increased 5 beta-DHT formation. Similarly, using 5 alpha-DHT as substrate, 5 alpha-diol formation was inhibited. Microsomal and low speed pellets with added cofactors formed products which recrystallized with either etiocholanolone or androsterone from [3H]T or [3H]DHT, respectively. Little product was formed without cofactor. Whole liver homogenates produced 5 beta-reduced products from [3H]T in the presence of an NADPH generating system whereas kidney homogenates produced 5 alpha-reduced products. These data provide new information on the capacity of fetal monkey liver and kidney to metabolize androgens. The 3 alpha-reductases are cytosolic. The 5 alpha- and 5 beta-reductases are mostly in the low speed pellet but are sufficiently represented in cytosols to mediate diol formation. The 17-hydroxysteroid dehydrogenases are in the microsomal fraction. Our results suggest that 5 alpha-DHT is the active androgen in fetal liver since testosterone is metabolized to 5 beta-DHT and 5 beta-diol which are inactive androgens.
J Steroid Biochem Mol Biol 1991 Apr
PMID:Androgen metabolism by hepatic and renal tissues of the fetal rhesus monkey. 203 65

To investigate the effects of sex hormones on 5 alpha-reductase, we examined 5 alpha-reductase mRNA content and enzyme activity in the adrenal cortex of peripubertal male and female rats. In male rats, the influence of castration or hormone-replacement treatment with dihydrotestosterone (5 alpha-DHT) on 5 alpha-reductase was assessed. To stimulate ovarian sex hormone production in immature female rats, the effect of a single injection of 5 IU pregnant mare serum gonadotrophin (PMSG) on 5 alpha-reductase was examined. The efficacy of the treatments was demonstrated by measuring serum LH and ventral prostate weight in male rats, and serum oestradiol and ovarian weight in female rats. Growth hormone was also measured across all treatments in male and female rats. Adrenal 5 alpha-reductase mRNA levels were determined by RNA blot analysis utilizing a rat 5 alpha-reductase cDNA as probe. 5 alpha-Reductase enzyme activity was estimated by isolating [3H]5 alpha-DHT by thin-layer chromatography after incubation with [3H]testosterone. The identity of the [3H]5 alpha-DHT formed was demonstrated by recrystallization of the derivatized DHT to constant specific activity. In controls, adrenal cortical 5 alpha-reductase mRNA content was nearly four times higher in immature female rats compared with intact peripubertal males. Castration resulted in a sevenfold increase in adrenal 5 alpha-reductase mRNA content compared with that in intact controls, while in DHT-injected castrated animals the mRNA level was nearly undetectable. The content of adrenal 5 alpha-reductase mRNA in anoestrous rats was nearly four times higher than in PMSG-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Endocrinol 1991 Apr
PMID:Rat adrenal 5 alpha-reductase mRNA content and enzyme activity are sex hormone dependent. 204 43

Pig testicular 20 beta-hydroxysteroid dehydrogenase (20 beta-HSD) has also 3 alpha- and 3 beta-HSD (3 alpha/beta-HSD) activities. The purified 20 beta-HSD preparation from neonatal pig testes could catalyze the conversion of 5 alpha-dihydrotestosterone (5 alpha-DHT) in the presence of beta-NADPH to 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol at the ratio of 4:3, and the specific 3 alpha/beta-HSD activity of 20 beta-HSD for 5 alpha-DHT was about 10 or 15 times larger than the 20 beta-HSD activities for 17 alpha-hydroxypregn-4-ene-3,20-dione (17 alpha-hydroxyprogesterone) or progesterone, respectively. The result indicates that the testicular 20 beta-HSD has high 3 alpha(axial, 3R)- and 3 beta(equatorial, 3S)-HSD activity. The testicular 20 beta-HSD could catalyze the reversible conversion of various 5 alpha- or 5 beta-dihydrosteroids which have a 3-carbonyl or 3-hydroxyl group with beta-NADP(H) as the preferred cofactor. The enzyme transferred the 4-proS hydrogen of NADPH to the 5 alpha-DHT for both 3 alpha- and 3 beta-hydroxylation and it was the same as the 20 beta-hydroxylation of 17 alpha-hydroxyprogesterone. Although the 3 alpha/beta-HSD activity has been known to be present in 3 alpha,20 beta-HSD of Streptomyces hydrogenans, the enzymological properties for 3 alpha/beta-HSD activity catalyzed by testicular 20 beta-HSD were different from the properties for 3 alpha/beta-HSD activity catalyzed by prokaryotic 3 alpha, 20 beta-HSD with respect to the specificity of the catalytic reaction and the cofactor requirement.
J Steroid Biochem Mol Biol 1991 Jun
PMID:20 beta-hydroxysteroid dehydrogenase of neonatal pig testis: 3 alpha/beta-hydroxysteroid dehydrogenase activities catalyzed by highly purified enzyme. 206 95

Antiandrogens, preventing androgen action at target tissue level, are used in the treatment of various androgen-dependent diseases. Pharmacologically these substances have either a steroidal structure, like cyproterone acetate (CPA) and spironolactone (SPL), or a non-steroidal structure, like flutamide (FLU). In women with hyperandrogenism (PCO syndrome, idiopathic hirsutism, acne), clinical benefit may be obtained with CPA, which also displays a progestational activity and an antigonadotropic effect. CPA (25-50 mg/day) is used in combination with ethinyl-estradiol (EE) (20-30 micrograms/day) in reversed sequential regimen. SPL, less effective than CPA may be employed in moderate hirsutism and acne at dosages of 100-200 mg/day. During SPL treatment menstrual irregularities are frequent: in this case an association with oral contraceptives is indicated. SPL + bromocriptine (2.5-5 mg/day) has been experienced with success in PCO syndrome. The pure antiandrogen FLU, inducing progressive increase in LH and testosterone secretion, may be used only in combination with oral contraceptives. In men antiandrogens have been tested in BPH and prostatic carcinoma. In BPH the decrease in nuclear receptors and DHT nuclear content during CPA or FLU may represent the rational base of the medical treatment. An improvement in urinary obstructive manifestation has been observed with CPA alone or associated with tamoxifen (100 mg + 100 mg day). In advanced prostatic carcinoma antiandrogens represent a good alternative to estrogen therapy with less side effects and in combination with surgical or medical castration (LH-RH analogues) achieve a complete androgen blockade. An increase in the percentage of remissions and survival has been reported.
J Steroid Biochem Mol Biol 1990 Nov 20
PMID:Antiandrogens: clinical applications. 214 59

Neurons expressing the tryptophan hydroxylase (TPH) mRNA within the raphe nuclei of control rats showed a distribution similar to that observed using an antibody for TPH. Numerous packed cells expressing the TPH mRNA were observed in the ventral and dorsal zone of the nucleus raphe dorsalis (NDR) and in the pars dorsalis of the nucleus centralis superior (NCS) whereas fewer and more scattered neurons were found in the pars medialis of NCS. Five days after the intracerebroventricular injection of 5,7-dihydroxytryptamine (5,7-DHT), which markedly reduced the serotonin (5-HT) content in the hippocampus, caudate putamen and cortex, the hybridization signal had completely disappeared in the dorsal region of the NDR. In the ventromedial region, above and between the medial longitudinal fasciculus (MLF), which includes the pars dorsalis of NCS, there was a partial decrease of cell number and a marked increase of the grain density over spared neurons. No significant change was noted in the number of TPH-positive cells and hybridization signal in individual neurons of the pars medialis of NCS. Consistent with previous evidence of increased TPH activity in the residual 5-HT terminals, the present study shows that synthesis of the TPH mRNA may be augmented in some neurons surviving the lesion.
Brain Res Mol Brain Res 1990 Oct
PMID:Increased tryptophan hydroxylase mRNA in raphe serotonergic neurons spared by 5,7-dihydroxytryptamine. 217 12


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