Showing papers on "Hydroxysteroid dehydrogenase published in 1987"
TL;DR: The Y' bile acid binders are 3 alpha-HSD, which preferentially and stereospecifically catalyze the reduction of 3-oxo-bile acids to 3alpha-hydroxy bile acids.
Abstract: Rat Y' bile acid binders (33 kD) have been previously recognized as cytosolic bile acid binding proteins (Sugiyama, Y., T. Yamada, and N. Kaplowitz, 1983, J. Biol. Chem., 258:3602-3607). We have now determined that these Y' binders are 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSD), bile acid-metabolizing enzymes. 3 alpha-HSD activity copurified with lithocholic acid-binding activity after sequential gel filtration, chromatofocusing, and affinity chromatography. Three peaks of 3 alpha-HSD activity (I, II, III) were observed in chromatofocusing and all were identified on Western blot by a specific Y' binder antiserum. 3 alpha-HSD-I, the predominant form, was purified and functioned best as a reductase at pH 7.0 with a marked preference for NADPH. Michaelis constant values for mono- and dihydroxy bile acids were 1-2 microM, and cholic acid competitively inhibited the reduction of 3-oxo-cholic acid. Under normal redox conditions, partially purified 3 alpha-HSD-I and freshly isolated hepatocytes catalyzed the rapid reduction of 3-oxo-cholic to cholic acid without formation of isocholic acid, whereas the reverse reaction was negligible. The Y' bile acid binders are therefore 3 alpha-HSD, which preferentially and stereospecifically catalyze the reduction of 3-oxo-bile acids to 3 alpha-hydroxy bile acids.
62 citations
TL;DR: The present data indicate that differential intracellular metabolism of steroid hormones may have some influence on availability of estradiol at nuclear sites in postmenopausal women and may provide sufficient estrogenic stimulus to enhance the growth and progression of breast tumors.
Abstract: Total and subcellular (cytosol and nuclear) concentrations of estrone (E1), estradiol (E2), and androstenedione were determined in non-malignant (n = 61) and malignant (n = 65) human breast tissues obtained from post-menopausal women. The 17 beta-hydroxysteroid dehydrogenase (17 beta-OH-SDH) activity was determined in 800g supernatant fraction. Total estrogens, E1 and E2 levels and 17 beta-OH-SDH activity were significantly (p less than 0.005, 0.0005, 0.001, respectively) higher in malignant than in non-malignant breast tissues. We failed to observe significant changes in subcellular steroid concentrations or enzyme activity associated with patients' obesity or tumor estrogen receptor status. When the steroid levels were analyzed in relation to clinical staging of the disease, nuclear contents of estradiol were significantly higher (p less than 0.005) in Stage-IV patients than in those with less advanced disease (Stages I to III). 17 beta-OH-SDH activity was significantly (p less than 0.001) lower in patients with advanced disease than in those with relatively less advanced (Stages I to III) disease and was positively correlated with tissue concentration of androstenedione. Our present data indicate that differential intracellular metabolism of steroid hormones may have some influence on availability of estradiol at nuclear sites. In postmenopausal women, local interconversion of estrogens may provide sufficient estrogenic stimulus to enhance the growth and progression of breast tumors.
24 citations
TL;DR: C. scindens is the first bacterial species of the normal human intestinal flora reported to elaborate inducible steroid-17-20-desmolase and 20 alpha-hydroxysteroid dehydrogenase activities and the results of cofactor, substrate specificity and induction studies suggest that these two activities may reside in the same enzyme complex.
17 citations
TL;DR: The reaction of the 6-hydroxylated bile acid, hyodeoxycholic acid, and its 6-O-glucuronide conjugate with 3 alpha-hydroxysteroid dehydrogenase was examined and it was established that 6-Hydroxylation itself did not significantly affect the enzyme reaction.
4 citations
3 citations
TL;DR: The results suggested that the conversion of pregnenolone into progesterone may proceed in the trophoblast of the cat placenta and support the fact that ovariectomy after day 45 or 49 of gestation did not interrupt pregnancy.
Abstract: The distribution of hydroxysteroid dehydrogenase (HSD) was examined histochemically in the placenta and ovary of the cat at 14 gestational stages to discuss the possibility of steroidogenesis in the cat placenta. The enzymes investigated in this study were Δ5-3β-HSD, 17β-HSD, 20α-HSD, 20β-HSD and G-6-PDH. The activity of Δ5-3β-HSD was detected in the trophoblast of placental labyrinth and junctional zone. The activity of Δ5-3β-HSD was weak at the early stage of gestation, but being gradually increased with the progress of gestation. The activity was strongest at the stage of an 88-mm fetus in CRL (day 45), then decreased slightly toward term. No activity of 17β-HSD was detected in the trophoblast, but a weak activity was detected in the glandular epithelium, persisting throughout pregnancy. In the corpus luteum, the activity of Δ5-3β-HSD was strong or moderate until the stage of an 80-mm fetus (day 43), then abruptly decreased toward term. These results suggested that the conversion of pregnenolone into progesterone may proceed in the trophoblast of the cat placenta and support the fact that ovariectomy after day 45 or 49 of gestation did not interrupt pregnancy.
2 citations
2 citations
Journal Article•
2 citations
2 citations
01 Jan 1987
TL;DR: Because of its broad spectrum of biological activities and its potential usage in treating bone marrow failure, there was considerable interest in isolating the human homologue of murine IL-3.
Abstract: Interleukin 3 (IL-3) is a member of the family of colony stimulating factors (CSFs) responsible for regulating hematopoiesis (1). It is a T cell-derived lymphokine that was first defined by its ability to induce 20-α- hydroxysteroid dehydrogenase (20-α-SDH) in spleen cells of neonatal nude mice (2). IL-3 has been extensively characterized in the murine system. The protein was purified to homogeneity and both cDNA and genomic clones were subsequently isolated (3, 4, 5). With the availability of homogeneous protein, it has became apparent that this lymphokine is active in a variety of assays and is probably identical to a number of factors defined in other assay systems (6, 7). In vivo studies with recombinant murine IL-3 have indicated that IL-3 can stimulate erythropoiesis as well as myelopoiesis in both normal and myelo-suppressed mice (8, 9). Because of its broad spectrum of biological activities and its potential usage in treating bone marrow failure, there was considerable interest in isolating the human homologue of murine IL-3.
2 citations
TL;DR: In mutants with altered activity/inducibility of 17β- and 20β-HSD only one DNA-binding protein still showed an altered DNA affinity in response to estradiol-treatment and this in only one strain, while in other mutants the DNA affinity was not altered during induction withEstradiol, but theDNA affinity of protein 23 varied between low, low-and-high, and high affinity, depending on the strain.
Abstract: Treatment of the wild-type strain HY 0 of Streptomyces hydrogenans with estradiol, a specific inducer of 3β,17β-hydroxysteroid dehydrogenase (17β-HSD) formation, caused several soluble proteins to bind to DNA-cellulose with altered affinity. Hydrocortisone which induces biosynthesis of 3α,20β-hydroxysteroid dehydrogenase (20β-HSD), and progesterone which induces production of both 17β- and 20β-HSD, had no effect on DNA-binding properties of the proteins. In mutants with altered activity/inducibility of 17β- and 20β-HSD only one DNA-binding protein (protein 23) still showed an altered DNA affinity in response to estradiol-treatment and this in only one strain. In other mutants the DNA affinity was not altered during induction with estradiol but the DNA affinity of protein 23 varied between low, low-and-high, and high affinity, depending on the strain. In the mutant where DNA affinity was altered by estradiol treatment the change was opposite to that found in the wild type.
TL;DR: This work examined maturational changes in the activities of two enzymes affecting testosterone accumulation, I7p-HSD and Sa-reductase, in two Leydig cell bands isolated on metrizamide gradients to partially address this question.
Abstract: Previous studies using Metrizamide or Percoll gradients identified two or more bands of Leydig cells in adult rodents, with different densities and functional characteristics.'-' Other studies suggest, however, that Leydig cells localizing at the less dense regions represent damaged cell^,^.^ thus implying only a single Leydig cell population. This question is difficult to resolve, because the methods of dispersion and isolation affect the quality and yield of cells i ~ o l a t e d . ~ . ~ To partially address this question, we examined maturational changes in the activities of two enzymes affecting testosterone accumulation, I7p-HSD and Sa-reductase, in two Leydig cell bands isolated on metrizamide gradients. We reasoned that if these Leydig cells were functionally different, there might be distinct developmental patterns for the two enzymes. Collagenase-dispersed interstitial cells, from Sprague-Dawley rats ( 18-73 days old), were centrifuged on continuous (0-32%) Metrizamide gradients to isolate band 3 cells (B3) and band 2 cells (B2), representing population I1 and population I Leydig cells, respective1y.I Sa-Reductase activity was estimated using 10 pM [3H]testosterone (0.5 pCi) as substrate and incubating intact cells for 30 min at 34°C. The products, dihydrotestosterone (DHT), Sa-androstan-3a, 17P-diol (3adiol), and Sa-androstan-3p, 17/3-diol(3p-diol) were isolated by thin-layer chromatography (TLC). Incubation conditions to estimate I7P-HSD activity were identical, except androstenedione was isolated. 5a-Reductase activity in B2 cells was 0.028 nmol/30 min/lOs cells on day 18, increased to peak at 0,148 * 0.007 nmol on day 35, decreased to 0.018 * 0.008 nmol on day 53, and then stabilized (FIG. 1 , panel A). The pattern of 5a-reductase activity for B3 cells was similar. Activity was 0.101 nmol/30 min/105 cells on day 18, increased to 1.404 ? 0.083 nmol on day 35, decreased to 0.084 ? 0.014 nmol on day 53, and then stabilized (FIG. I , panel B). Although the pattern of 5areductase was similar for both bands, for each age, a greater percentage of DHT was converted to 3aand 3P-diol in B2 cells. The developmental pattern of 17pHSD activity was similar to 5a-reductase for both B2 and B, cells. 17P-HSD activity in B2 cells was 0.010 nmol/30 min/lO5 cells on day 24, increased to 0.148 ? 0.028 nmol on day 35, and then decreased to 0.01 1 -t 0.002 nmol on day 73 (FIG.