Showing papers on "Hydroxysteroid dehydrogenase published in 1993"
TL;DR: The compartmentalization of two strictly correlated enzymes in separate central nervous system cell populations suggests the simultaneous participation of neurons and glial cells in the 5 alpha-reductive metabolism of testosterone and possibly other hormonal steroids (e.g. progesterone, corticoids, etc.).
Abstract: The activities of the 5 alpha-reductase [the enzyme that converts testosterone into dihydrotestosterone (DHT)] and 3 alpha-hydroxysteroid dehydrogenase [the enzyme that converts DHT into 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol)] have been evaluated in primary cultures of neurons, oligodendrocytes, and type 1 and 2 astrocytes obtained from fetal or neonatal rat brain. All cultures were used on the fifth day. The formation of DHT and 3 alpha-diol was evaluated by incubating the different cultures with [14C]testosterone or [14C]DHT as substrates. The results obtained indicate that the formation of DHT takes place preferentially in neurons; however, type 2 astrocytes and oligodendrocytes also possess considerable 5 alpha-reductase activity, while type 1 astrocytes show a much lower enzymatic activity. A completely different localization was observed for 3 alpha-hydroxysteroid dehydrogenase. The formation of 3 alpha-diol appears to be mainly, if not exclusively, present in type 1 astrocytes. 3 al...
149 citations
TL;DR: It now is apparent that a family of closely related genes encode for 3β- hydroxysteroid dehydrogenase (3βHSD), and studies on the regulation of these genes are in their infancy, but the regulation appears multifactorial.
Abstract: It now is apparent that a family of closely related genes encode for 3β- hydroxysteroid dehydrogenase (3βHSD). Studies on the regulation of these genes are in their infancy, but the regulation appears multifactorial. The various 3βHSD genes are expressed principally in a tissue-specific manner likely involving separate mechanisms of regulation. To date, two human 3βHSD genes and their products have been characterized; type I is expressed in placenta, sebaceous glands, and several other nonendocrine tissues, whereas the type II isoform is the principal 3βHSD of adrenal cortex and gonads.
85 citations
TL;DR: The metabolism of estrogens catalyzed by human placental 17 beta-hydroxysteroid dehydrogenase transiently expressed in COS-m6 cells was studied, and the properties of the enzyme were compared with those of an endogenous hydroxysteroid dehydration enzyme expressed in the cells, suggesting that different 17HSD enzymes exist, with differential estrogen substrate specificities in cultured cells.
Abstract: The metabolism of estrogens catalyzed by human placental 17 beta-hydroxysteroid dehydrogenase (17HSD) transiently expressed in COS-m6 cells was studied, and the properties of the enzyme were compared with those of an endogenous hydroxysteroid dehydrogenase (HSD) expressed in the cells In cultured cells, the endogenous HSD had almost exclusively oxidative activity, converting estradiol to estrone (oxidative and reductive activity, 084 +/- 0164 and 0034 +/- 001 nmol/mg proteinh, respectively) This was, nevertheless, opposed to the activity of the transiently expressed human placental 17HSD, as a high reductive activity (086 +/- 030 nmol/mg proteinh) appeared in the cells after transfection, whereas oxidative activity was not significantly induced In the different transfections, the reductive activity was induced 13- to 34-fold, and the oxidative activity in the 17HSD-transfected cells was 65-162% of that in the mock-transfected cells Thus, in cultured cells, these two enzymes preferentially cata
70 citations
TL;DR: The enzyme 17β,20α-hydroxysteroid dehydrogenase may be an important regulator of the local estrogen/progesterone ratio in fetal membranes around the time of parturition.
58 citations
TL;DR: The kinetics of several potential inhibitors of estrone sulfatase and 17 beta-hydroxysteroid dehydrogenase in vitro in rat breast tumors are characterized and compared to those in human tissues and it is shown that blockade of enzyme action is significant in vitro and could also be in vivo.
57 citations
TL;DR: The cloning, sequencing and overexpression of the (3-17)beta hydroxysteroid dehydrogenase gene of Pseudomonas testosteroni is described and found to contain an open reading frame of 765 base pairs that corresponds to a protein of 254 amino acid residues.
44 citations
TL;DR: Evidence is provided of powerful interactive effects between steroidal and paracrine control of human breast epithelial cells in vitro and a synergy between the 2 factors is indicated.
26 citations
TL;DR: Palbinone, a novel terpenoid isolated from the roots of Paeonia albiflora, showed a strong inhibitory activity on the reduced from of nicotinamide adenine dinucleotide phosphate (NADPH)-linked 3α-hydroxysteroid dehydrogenase(3α-HSD) of rat liver cytosol.
Abstract: Palbinone, a novel terpenoid isolated from the roots of Paeonia albiflora, showed a strong inhibitory activity on the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH)-linked 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) of rat liver cytosol. The structures of palbinone and a known compound, paeonilactone-B isolated from the active fraction of this plant were determined by the use of 2D NMR techniques (1H-1H COSY, 1H-13C COSY, 1H-13C long-range COSY, and HMBC).
20 citations
TL;DR: The observations suggest that tamoxifen may reduce intratissular levels of E2 by directly increasing oxidative 17-HSD activity and by blocking the actions of paracrine factors such as IL-6 which increase reductive 17- HSD activity.
19 citations
10 citations
30 Jun 1993
TL;DR: The results suggest the presence of essential cysteine and lysine residues at or near the coenzyme-binding site and that of essential histidine residue(s) in the catalytic region of the active site of mouse liver 17 beta-hydroxysteroid dehydrogenase.
Abstract: Monomeric 17 beta-hydroxysteroid dehydrogenase from mouse liver was rapidly inactivated by 5,5'-dithiobis(2-nitrobenzoic acid) and 2,4,6-trinitrobenzene-1-sulfonate, and the absorption spectra of the inactivated enzymes indicated that cysteine and lysine residues were modified. The kinetics of inactivation and spectrophotometric quantification of the modified residues suggested that complete inactivation was caused by modification of two cysteine residues or one lysine residue per active site. The inactivation by the two reagents was protected by NADP+ and some coenzyme analogs, but not by a steroid substrate, testosterone. Moreover, chemical modification by diethyl pyrocarbonate also produced inactivation of the enzyme, and showed a difference spectrum with a peak at 242 nm characteristic of N-carbethoxyhistidine residues, which decreased with the addition of hydroxylamine. The inactivation by this reagent, following pseudo-first-order kinetics, was protected partially by either NADP+ or testosterone and completely in the presence of both the coenzyme and substrate. The results suggest the presence of essential cysteine and lysine residues at or near the coenzyme-binding site and that of essential histidine residue(s) in the catalytic region of the active site of mouse liver 17 beta-hydroxysteroid dehydrogenase.
TL;DR: Coenzyme (NADP+) completely protected the enzyme from this inactivation by disulfides, but neither of the substrates (androsterone and benzenedihydrodiol) did and the activity of inactivated enzyme was restored by treatment with thiols such as DTT (dithiothreitol) or GSH.
Abstract: 3 alpha-Hydroxysteroid dehydrogenase (EC 1.1.1.50), purified to homogeneity from rat liver, was strongly inactivated by incubation with a disulfide such as GSSG, L-cystine or L-cystamine, as well as an SH-reagent such as DTNB (5,5'-dithiobis(2-nitrobenzoic acid)), NEM (N-ethylmaleimide) or iodoacetic acid. The inactivation advanced with incubation time. Coenzyme (NADP+) completely protected the enzyme from this inactivation by disulfides, but neither of the substrates (androsterone and benzenedihydrodiol) did. The activity of inactivated enzyme was restored by treatment with thiols such as DTT (dithiothreitol) or GSH. In the GSH/GSSG redox buffer, the enzyme existed in an equilibrium between active (reduced) and inactive (oxidized) forms.
TL;DR: From the absorption spectrum result, microsomal carbonyl reduct enzyme closely resembles cytochrome P-450 reductase, a novel enzyme which can act on both testosterone and androsterone at low concentration.
TL;DR: A 2.5-fold increase of specific activity was obtained during solubilization under optimal conditions and the soluble fraction contained more than 90% of the enzymatic activity.
TL;DR: This observation contradicts coexisting, separate binding sites, one for each activity, and suggests a conformation shift around one binding region prompted by products of the dehydrogenase reaction may create the isomerase activity.
TL;DR: The deduced amino acid sequence of the enzyme indicated that the molecular weight is 26,778.8%, and the transformant of E. coli DH1 harboring plasmid with a 1.8-kbp fragment in pUC19 showed about 200-fold-higher enzyme activity than that of the host.
Abstract: 7a-Hydroxysteroid dehydrogenase (EC 1.1.1.159), which acts on the hydroxyl group at position 7 of the steroid frame was found in Eschenichia coli (3) and purified from a cell extract (4). The gene encoding this enzyme, hdhA4, was cloned and the entire nucleotide sequence of an inserted PstI-BamHI fragment of pSD3 was sequenced (5). The mature-enzyme-encoding sequence was found to start at a GTG initiation codon and to comprise 765 bp. The deduced amino acid sequence of the enzyme indicated that the molecular weight is 26,778. The transformant of E. coli DH1 harboring plasmid with a 1.8-kbp fragment in pUC19 showed about 200-fold-higher enzyme activity than that of the host.
TL;DR: The results of the kinetic study, and regulation by various steroids in the present study, indicate that oxidation of estradiol or reduction of estrone is probably mediated via different forms of 17β-OH-SDH.