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)

11 beta-Hydroxysteroid dehydrogenase (11 beta HSD) catalyzes the conversion of cortisol to cortisone and plays an important role in the mammalian kidney in regulating cortisol access to the mineralocorticoid receptor. 11 beta HSD-deficient states, such as the syndrome of apparent mineralocorticoid excess (AME), and licorice ingestion result in hypertension in which cortisol acts as a mineralocorticoid. A gene and complementary DNA sequence encoding type I human 11 beta HSD have been described, but this gene is normal in patients with AME. Separate 11 beta HSD isoforms have been described in rat and rabbit kidney, but 11 beta HSD has not been characterized in human kidney. Kinetic analysis of 11 beta HSD activity in human fetal kidney microsomes revealed only a high affinity isoform (apparent Km, 60 nmol/L for cortisol, 13 nmol/L for corticosterone), the activity of which was exclusively nicotinamide adenine dinucleotide (NAD) dependent. No 11-oxo-reductase activity was seen in either renal homogenates or microsomes. 11 beta-Dehydrogenase activity was inhibited by glycyrrhetinic acid (the active ingredient in licorice) in a competitive fashion, with a Ki of 8.7 nmol/L. This 11 beta HSD isoform was clearly distinct from the type I h11 beta HSD enzyme, in that COS-1 cells transfected with type I h11 beta HSD complementary DNA expressed a low affinity (apparent Km, 2.13 mumol/L) isoform, the activity of which was NAD phosphate dependent. 11-Oxo-reductase activity was present in intact transfected cells (apparent Km for cortisone, 0.36 mumol/L), but not in cell lysates. In contrast to the cloned, low affinity, type I h11 beta HSD enzyme, human kidney contains a high affinity NAD-dependent 11 beta HSD isoform. It seems probable that this isoform is responsible for protecting the renal mineralocorticoid receptor from glucocorticoid excess, and a defect in its activity may explain AME.
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PMID:Human kidney 11 beta-hydroxysteroid dehydrogenase is a high affinity nicotinamide adenine dinucleotide-dependent enzyme and differs from the cloned type I isoform. 804 66

A bile acid-inducible NADP-linked 7 alpha-hydroxysteroid dehydrogenase (7 alpha-HSDH) from Clostridium sordellii ATCC 9714 was purified 310-fold by ion-exchange, gel filtration, and dye-ligand affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the purified enzyme showed one predominant peptide band (30,000 Da). The N-terminal sequence was determined, and the corresponding oligonucleotides were synthesized and used to screen EcoRI and HindIII genomic digests of C. sordellii. Two separate fragments (4,500 bp, EcoRI; 3,200 bp, HindIII) were subsequently cloned by ligation to pUC19 and transformation into Escherichia coli DH5 alpha-MCR. The EcoRI fragment was shown to contain a truncated 7 alpha-HSDH gene, while the HindIII fragment contained the entire coding region. E. coli clones containing the HindIII insert expressed high levels of an NADP-linked 7 alpha-HSDH. Nucleotide sequence analyses suggest that the 7 alpha-HSDH is encoded by a monocistronic transcriptional unit, with DNA sequence elements resembling rho-independent terminators located in both the upstream and downstream flanking regions. The transcriptional start site was located by primer extension analysis. Northern (RNA) blot analysis indicated that induction is mediated at the transcriptional level in response to the presence of bile acid in the growth medium. In addition, growth-phase-dependent expression is observed in uninduced cultures. Analysis of the predicted protein sequence indicates that the enzyme can be classified in the short-chain dehydrogenase group.
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PMID:Characterization and regulation of the NADP-linked 7 alpha-hydroxysteroid dehydrogenase gene from Clostridium sordellii. 805 Sep 99

A novel steroid-inducible 17 alpha-hydroxysteroid dehydrogenase (17 alpha-HSDH) has been purified over 850-fold from an intestinal Eubacterium sp. VPI 12708. The purified protein has a subunit molecular mass of 42,000 daltons and a native molecular weight (M(r)) of 160,000 as estimated by gel filtration chromatography. Enzyme activity was induced by growth in the presence of androstenedione or cholic acid, but not deoxycholic acid. Enzymatic activity required anaerobic conditions and was highly specific for NADP+ and the 17 alpha-hydroxy group of C-19 steroids. Estimated Km values were 31 microM and 70 microM for androstenedione and epitestosterone, respectively. Vmax values were estimated to be 3250 nmol/min per mg protein and 1800 nmol/min per mg protein for the reductive and oxidative reactions, respectively. The pH optima for both the oxidative and reductive reactions ranged between 5.5 and 7.0. Treatment with EDTA completely inactivated 17 alpha-HSDH activity but activity was partially restored by the addition of either Mg2+ (1 mM) or Zn2+ (10 mM). The N-terminal amino acid sequence analysis of purified enzyme suggests that 17 alpha-HSDH may belong to a disulfide reductase gene family.
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PMID:Purification and characterization of a novel 17 alpha-hydroxysteroid dehydrogenase from an intestinal Eubacterium sp. VPI 12708. 807 14

3 alpha-Hydroxysteroid dehydrogenase (3 alpha HSD) is one of the main enzymes involved in the metabolism of the active androgen, dihydrotestosterone (DHT). 3 alpha HSD catalyzes the reversible reduction of DHT to 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha DIOL). The equilibrium of 3 alpha HSD reductive and oxidative activity is an important factor in the regulation of intracellular levels of DHT. In this study, we determined the kinetic characteristics of 3 alpha HSD in the subcellular fractions of female rat liver and abdominal skin. The enzyme expressed its activity in the cytosol and microsomal fractions of both of these tissues. It showed higher activity with the phosphorylated cofactors, NADPH and NADP, and was inhibited by indomethacin. The Vmax values of 3 alpha HSD in the cytosol were 10-fold higher than the Vmax values in the microsomes in both the liver and skin. In both tissues, the Km values with DHT as the substrate (reductive) were lower than the Km with 3 alpha DIOL as the substrate (oxidative). Although the Vmax values of the oxidative reaction were higher than the Vmax values of the reductive reaction in both liver and skin, the low Km values and the higher Vmax/Km ratio for DHT indicated that the reduction of DHT to 3 alpha DIOL was the favored reaction. The enzyme kinetics of 3 alpha HSD suggest that neither tissue accumulates DHT, but promptly converts it to 3 alpha DIOL.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:3 Alpha-hydroxysteroid dehydrogenase activity in rat liver and skin. 807 80

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) was demonstrated specifically in the spiral ligament of the cochlear membranous labyrinth by enzyme assay, Western blotting, and immunocytochemistry. Other cochlear regions and the vestibular membranous labyrinth were devoid of 11 beta-HSD. Spiral ligament 11 beta-HSD exerted predominantly an oxidative activity and was NADP specific, which is similar to 11 beta-HSD in most other tissues. 11 beta-HSD was colocalized with mineralocorticoid and glucocorticoid steroid receptors in the spiral ligament. 11 beta-HSD may control steroid binding to these inner ear steroid receptors and, in addition, may regulate steroid receptor binding in the adjacent stria vascularis in paracrine fashion.
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PMID:11 beta-Hydroxysteroid dehydrogenase in the rat inner ear. 814 Dec 86

The modulation of the intracellular glucocorticoidal effect on surfactant synthesis of the fetal lung by the metabolic capacity of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) could be an important factor in lung maturation. The kinetic properties of microsomal 11 beta-HSD of the rat lung are characterized with respect to product inhibition, substrate specificity, effect of electrolytes or trace elements, and the dependence of the oxidase reductase (OR) ratio on incubation conditions. With NADP+ product inhibition of the reductase was demonstrated. The most common trace elements and electrolytes exhibited no effect on the activity of 11 beta-HSD. It is shown that the OR ratio was strongly dependent on assay conditions. With optimal assay conditions oxidase activity exceeds reductase activity in adult and fetal rat lung microsomes (OR ratio > 1). Thus, glucocorticoids are mainly metabolized to their inactive forms. The enzyme activity in the adult is about 10 times higher than in the fetal lung. The low enzyme activity in fetal lungs could be the reason why the glucocorticoidal effects on surfactant synthesis are not suppressed despite the predominance of oxidase activity.
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PMID:11-beta-Hydroxysteroid dehydrogenase of rat lung: enzyme kinetic, oxidase-reductase ratio, electrolyte and trace element dependence. 819 74

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

Isotope exchange kinetics at chemical equilibrium were used to probe the mechanisms of substrate binding and regulatory behavior of homoserine dehydrogenase-I from Escherichia coli. At pH 9.0, 37 degrees C, Keq = 100 (+/- 20) for the catalyzed reaction: L-aspartate-beta-semialdehyde + NADPH + H+ = L-homoserine + NADP+. Saturation curves for the exchange reactions, [14C]L-homoserine <--> L-aspartate-beta-semialdehyde and [3H]NADP+ <--> NADPH were observed as a function of different reactant-product pairs, varied in constant ratio at equilibrium. The NADP+ <--> NADPH exchange rate was inhibited upon variation of pairs involving L-aspartate-beta-semialdehyde and L-homoserine, consistent with preferred order random binding of cofactors before amino acids. Optimal rate constants, derived by simulations of equilibrium isotope exchange kinetics data with the ISOBI program, indicate faster dissociation of amino acids than cofactors from the central complexes but nearly equal rates for association of cofactors and amino acids to free enzyme. Rate limitation of net turnover in both directions is determined by dissociation of cofactor from the E-cofactor complex. The allosteric modifier, L-threonine, produces distinctive perturbations of the saturation curves for isotope exchange, which were analyzed systematically with the ISOBI program. The best fit to the data was obtained by L-threonine inhibiting catalysis between the central complexes without altering substrate association-dissociation rates. Simulations also showed that rate-limiting catalysis suppresses the kinetic inhibition effects that are characteristic of preferred order substrate binding, producing patterns typical for a (rapid equilibrium) random kinetic scheme.
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PMID:Kinetic and regulatory mechanisms for (Escherichia coli) homoserine dehydrogenase-I. Equilibrium isotope exchange kinetics. 844 66

An abundant 37-kDa protein, which comprises up to 30% of the soluble proteins of the ovary, has been found to have 20 alpha-hydroxysteroid dehydrogenase (20 alpha HSD) activity. The steroidogenic enzyme 20 alpha HSD regulates the conversion of progesterone to 20 alpha-hydroxyprogesterone in many mammalian species. Complimentary DNA clones encoding a unique and abundant 20 alpha HSD were isolated from a mature rabbit ovary library using guinea pig antisera generated to the purified 37-kDa protein and from a 5' EcoRI fragment from the initial positive clone. A full-length cDNA clone of 1217 basepairs encoding a 323-amino acid protein with an estimated mol wt of 37 kilodaltons was obtained. Amino acid sequence data indicate a similarity to human chlordecone reductase, bovine lung prostaglandin F synthase, human aldose reductase, human aldehyde reductase, and frog lens rho-crystallin, placing rabbit ovarian 20 alpha HSD in the aldo-keto reductase family of proteins. Northern blot analysis demonstrated a 1.2-kilobase mRNA in the interstitial tissue of mature rabbit ovaries and, to a lesser extent, in corpora luteal tissue. 20 alpha HSD was expressed in bacteria as a recombinant protein and was shown to possess enzymatic activity, preferring NADP as a cofactor. These studies demonstrate that an abundant ovarian protein belonging to the superfamily of NADP-dependent aldo-keto reductases has 20 alpha HSD activity. This is the first example of an abundant crystallin-related protein with known enzymatic activity in a tissue other than the lens.
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PMID:Molecular cloning and expression of an abundant rabbit ovarian protein with 20 alpha-hydroxysteroid dehydrogenase activity. 824 25


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