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Query: UMLS:C0338671 (Steroids)
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The type 1 and type 2 isoforms of human 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) play a crucial role, respectively, in modulating glucocorticoid and mineralocorticoid hormone action. Deficiency of the 11 beta-HSD2 isoform, as described in the syndrome of apparent mineralocorticoid excess and following liquorice (glycyrrhetinic acid) or carbenoxolone ingestion, results in hypertension in which cortisol acts as a potent mineralocorticoid. Several studies have addressed the effects of progesterone, glycyrrhetinic acid, and their derivatives on 11 beta-HSD activity, but these were largely undertaken before the characterization of the 11 beta-HSD isoforms. The aim of this study was to evaluate the localization of 11 beta-HSD2 in human kidney and to study the effects of progesterone, glycyrrhetinic acid, and their related compounds on stable transfectants of the human 11 beta-HSD isoforms. Using an in-house sheep antibody against human 11 beta-HSD2, immunoperoxidase studies localized 11 beta-HSD2 to renal cortical and medullary collecting ducts. Glomeruli, vascular structures, loops of Henle, and proximal tubules were all negative. Confocal laser microscopy studies indicated both a cytoplasmic and nuclear localization for the enzyme within renal collecting ducts. The nuclear staining, which was intranuclear and was not associated with the nuclear membrane, accounted for 40% of the total cellular 11 beta-HSD2 immunoreactivity. Kinetic analysis of 11 beta-HSD activity in fetal kidney 293 cells stably transfected with h11 beta-HSD1/pcDNA3 or 11 beta-HSD2/pCR3, indicated, respectively, low-affinity dehydrogenase/oxoreductase activity (Km for F, 1.8 microM; Km for E, 270 nM) and high-affinity dehydrogenase activity (Km for F, 190 nM). The reductase activity of 11 beta-HSD1 was inhibited by 11 alpha-hydroxyprogesterone > carbenoxolone = glycyrrhetinic acid = progesterone > 11 beta-hydroxyprogesterone. The dehydrogenase activity of 11 beta-HSD2 was inhibited 11 alpha-hydroxyprogesterone = 11 beta-hydroxyprogesterone > glycyrrhetinic acid > carbenoxolone = progesterone. 11 beta-HSD2, expressed in the renal collecting duct, serves to protect the mineralocorticoid receptor (MR) in an autocrine fashion. The demonstration of a nuclear localization for what was thought to be principally a microsomal enzyme suggests that interaction between the MR and its ligand (either aldosterone or cortisol) may be a nuclear rather than a cytoplasmic event. The inhibitory effects of progesterone, glycyrrhetinic acid, and related compounds on 11 beta-HSD1 and 2 were similar, and it remains to be seen what implication these findings have for 11 beta-HSD1 action in tissues such as the liver and gonad and renal 11 beta-HSD2 activity in relation to sodium homeostasis and blood pressure control.
Steroids 1997 Jan
PMID:Human 11 beta-hydroxysteroid dehydrogenase: studies on the stably transfected isoforms and localization of the type 2 isozyme within renal tissue. 902 19

The syndrome of apparent mineralocorticoid excess (AME) is an inherited form of hypertension in which 11 beta-hydroxysteroid dehydrogenase (11-HSD) is defective. This enzyme converts cortisol to its inactive metabolite, cortisone. The deficiency allows mineralocorticoid receptors to be occupied by cortisol, because these receptors themselves have similar affinities for cortisol and aldosterone. There are two isozymes of 11-HSD, a liver (L) or type 1 isozyme with a relatively low affinity for steroids, and a kidney (K) or type 2 isozyme with high steroid affinity. Mutations in the gene for the kidney isozyme of 11-HSD have been detected in all kindreds with AME. We expressed enzymes carrying all known missense mutations in cultured cells and determined their activity. For each patient with AME, we compared the enzymatic activity predicted by the genotype with the ratio of cortisol to cortisone metabolites in the urine, (THF + aTHF)/THE. These were strongly correlated, suggesting that the biochemical phenotype of AME is largely determined by genotype. The K isozyme of 11-HSD is also expressed in high levels in the placenta, where its function is unclear. AME patients often have low birth weight. By analogy with AME, low placental 11-HSD K activity in humans might be a risk factor for low birth weight and subsequent hypertension. However, we found that there was no significant correlation between 11-HSD activity, mRNA levels, and either fetal or placental weight.
Steroids 1997 Jan
PMID:Molecular analysis of 11 beta-hydroxysteroid dehydrogenase and its role in the syndrome of apparent mineralocorticoid excess. 902 20

Short-chain dehydrogenase reductase (SDR) enzymes influence mammalian reproduction, hypertension, neoplasia, and digestion. The three-dimensional structures of two members of the SDR family reveal the position of the conserved catalytic triad, a possible mechanism of keto-hydroxyl interconversion, the molecular mechanism of inhibition, and the basis for selectivity. Glycyrrhizic acid, the active ingredient in licorice, and its metabolite carbenoxolone are potent inhibitors of bacterial 3 alpha, 20 beta-hydroxysteroid dehydrogenase (3 alpha, 20 beta-HSD). The three-dimensional structure of the 3 alpha,20 beta-HSD carbenoxolone complex unequivocally verifies the postulated active site of the enzyme, shows that inhibition is a result of direct competition with the substrate for binding, and provides a plausible model for the mechanism of inhibition of 11 beta-hydroxysteroid dehydrogenase and 15-hydroxyprostaglandin dehydrogenase by carbenoxolone. The structure of human 17 beta-hydroxysteroid dehydrogenase type 1 (17 beta-HSD) suggests the details of binding of estrone and 17 beta-estradiol in the active site of the enzyme and the possible roles of various amino acids in the catalytic cleft. The SDR family includes over 50 proteins from human, mammalian, insect, and bacterial sources. Only five residues are conserved in all members of the family, including the YXXXK sequence. X-ray crystal structures of five members of the family have been completed. When the alpha-carbon backbone of the cofactor binding domains of the five structures are superimposed, the conserved residues are at the core of the structure and in the cofactor binding domain, but not in the substrate binding pocket.
Steroids 1997 Jan
PMID:Structure and function of steroid dehydrogenases involved in hypertension, fertility, and cancer. 902 22

Mammalian 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSDs) inactivate circulating steroid hormones, and in target tissues regulate the occupancy of steroid hormone receptors. Molecular cloning indicates that 3 alpha-HSDs are members of the aldo-keto reductase (AKR) superfamily and display high sequence identity (> 60%). Of these, the most extensively characterized is rat liver 3 alpha-HSD. X-ray crystal structures of the apoenzyme and the E.NADP+ complex have been determined and serve as structural templates for other 3 alpha-HSDs. These structures reveal that rat liver 3 alpha-HSD adopts an (alpha/beta)8-barrel protein fold. NAD(P)(H) lies perpendicular to the barrel axis in an extended conformation, with the nicotinamide ring at the core of the barrel, and the adenine ring at the periphery of the structure. The nicotinamide ring is stabilized by interaction with Y216, S166, D167, and Q190, so that the A-face points into the vacant active site. The 4-pro-(R) hydrogen transferred in the oxidoreduction of steroids is in close proximity to a catalytic tetrad that consists of D50, Y55, K84, and H117. A water molecule is within hydrogen bond distance of H117 and Y55, and its position may mimic the position of the carbonyl of a 3-ketosteroid substrate. The catalytic tetrad is conserved in members of the AKR superfamily and resides at the base of an apolar cleft implicated in binding steroid hormone. The apolar cleft consists of a side of apolar residues (L54, W86, F128, and F129), and opposing this side is a flexible loop that contains W227. These constraints suggest that the alpha-face of the steroid would orient itself along that side of the cleft containing W86. Site-directed mutagenesis of the catalytic tetrad indicates that Y55 and K84 are essential for catalysis. Y55S and Y55F mutants are catalytically inactive, but still form binary (E.NADPH) and ternary (E.NADH.Testosterone) complexes; by contrast K84R and K84M mutants are catalytically inactive, but do not bind steroid hormone. The reliance on a Tyr/Lys pair is reminiscent of catalytic mechanisms proposed for other AKR members as well as for HSDs that belong to the short-chain dehydrogenase/reductase (SDR) family, in which Tyr is the general acid, with its pKa being lowered by Lys. Superimposition of the nicotinamide rings in the structures of 3 alpha-HSD (an AKR) and 3 alpha, 20 beta-HSD (an SDR) show that the Tyr/Lys pairs are positionally conserved, suggesting convergent evolution across protein families to a common mechanism for HSD catalysis. W86Y and W227Y mutants bind testosterone to the E.NADH complex, with effective increases in Kd of 8- and 20-fold. These data provide the first evidence that the side of the apolar cleft containing W86 and the opposing flexible loop containing W227 are parts of the steroid-binding site. Detailed mutagenesis studies of the apolar cleft and elucidation of a ternary complex structure will ultimately provide details of the determinants that govern steroid hormone recognition. These determinants could provide a rational basis for structure-based inhibitor design.
Steroids 1997 Jan
PMID:Structure and function of 3 alpha-hydroxysteroid dehydrogenase. 902 23

Studies of the regulation of androgen synthesis in steroidogenic cells have focused on both transcriptional and post-translational regulation of the proteins that catalyze these reactions: the P450c17 that catalyzes the production of DHEA or androstenedione in consecutive hydroxylase and lyase activities, and the 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) that catalyzes the conversion of androstenedione to testosterone. Our studies of the regulation of the CYP17 lyase activity at the molecular level have utilized species- and tissue-specific differences to identify target regulatory sequences. Adenovirus infection of rat CYP17 promoter/luciferase reporter gene constructs in primary cultures of rat adrenal and rat Leydig cells revealed a rat-specific domain between-1 and -108 bp that cause inhibition of both basal and cAMP-induced CYP17 transcription in the adrenal, but not the Leydig cell. In contrast, similar promoter constructs from other species exhibited substantial cAMP-induced transcriptional activity in the rat adrenal. Mutagenesis of the conserved region of the rat and human proteins reveals significant differences in the amino acid domains required for hydroxylase and lyase activities within and between the two species, consistent with their differential regulation of lyase activity. The 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) reaction requires a viable glucose transporter system for optimal activity, and a high-energy phosphate was discovered to be the requisite product of glucose metabolism in 17 beta-HSD activation. These studies have provided insight into potential mechanisms of control of androgen synthesis in the late steroidogenic pathway, at the transcriptional and post-translational levels.
Steroids 1997 Jan
PMID:Regulation of androgen synthesis: the late steroidogenic pathway. 902 27

17 beta-Hydroxysteroid dehydrogenases (17 beta-HSDs) are enzymes involved in both the activation and inactivation of androgens and estrogens. 17 beta-HSD type 1 shows a high specificity for C18 steroids and is the major isozyme in the granulosa cells of the ovary. Its role is to convert the inactive C18 steroid estrone to the active estrogen estradiol, which in turn locally promotes maturation of the follicle. In contrast, attenuation of estradiol action in the glandular epithelium of the secretory endometrium is achieved by expression of the oxidative type 2 isozyme that inactivates estradiol to estrone. An interesting feature of 17 beta-HSD type 2 is that the enzyme also possesses 20 alpha-HSD activity, i.e., it catalyzes the 20 alpha-oxidation of the inactive C21 steroid 20 alpha-dihydroprogesterone to the active progestin progesterone. As the type 2 enzyme is also active on androgens, it may play a general role in the peripheral inactivation of androgens and estrogens, thus determining their steady-state levels in target tissues. The reductive 17 beta-HSD type 3 is predominantly expressed in the testis and converts the inactive C19 steroid androstenedione to the active androgen testosterone. The importance of the type 3 enzyme in male steroid hormone physiology is underscored by the genetic disease 17 beta-HSD deficiency. Mutations in the 17 beta-HSD3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with normal male Wolffian duct structures but female external genitalia. To date, 15 mutations have been identified in 18 subjects with the disease.
Steroids 1997 Jan
PMID:Physiology and molecular genetics of 17 beta-hydroxysteroid dehydrogenases. 902 29

17 beta-Hydroxysteroid dehydrogenase (17 beta-HSD) controls the last step in the formation of all androgens and all estrogens. This crucial role of 17 beta-HSD is performed by at least five 17 beta-HSD isoenzymes having individual cell-specific expression, substrate specificity, regulation mechanisms, and reductive or oxidative catalytic activity. Both estrogenic and androgenic 17 beta-HSD activities were found in all 25 rhesus monkey and 15 human peripheral intracrine tissues examined. Type 1 17 beta-HSD is a protein of 327 amino acids catalyzing the formation of 17 beta-estradiol from estrone. Its x-ray structure was the first to be determined among mammalian steroidogenic enzymes. Initially crystallized with NAD, the crystal structure of type 1 17 beta-HSD has just been determined as a complex with 17 beta-estradiol, thereby illustrating the conformation of the substrate-binding site. Type 2 17 beta-HSD degrades 17 beta-estradiol into estrone and testosterone into androstenedione, and type 4 17 beta-HSD mainly degrades 17 beta-estradiol into estrone and androst-5-ene-3 beta, 17 beta-diol into dehydroepiandrosterone. Types 3 and 5 17 beta-HSD, on the other hand, catalyze the formation of testosterone from androstenedione in the testis and peripheral tissues, respectively. The various types of human 17 beta-HSD, because of their tissue-specific expression and substrate specificity, provide each peripheral cell with the necessary mechanisms to control the level of intracellular androgens and/or estrogens, a new area of hormonal control that we call intracrinology.
Steroids 1997 Jan
PMID:The key role of 17 beta-hydroxysteroid dehydrogenases in sex steroid biology. 902 30

Meiotic maturation of fish oocytes is induced by the action of maturation-inducing hormone (MIH). 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one (17 alpha,20 beta-DP) was identified as the MIH of several fish species, including salmonid fishes. The interaction of two ovarian follicle cell layers, the thecal and granulosa cell layers, is required for the synthesis of 17 alpha,20 beta-DP; the thecal layer produces 17 alpha-hydroxyprogesterone that is converted to 17 alpha,20 beta-DP in granulosa cells by the action of 20 beta-hydroxysteroid dehydrogenase (20 beta-HSD). The preovulatory surge of LH-like gonadotropin (GTH II) is responsible for rapid expression of 20 beta-HSD mRNA transcripts in granulosa cells. 17 alpha,20 beta-DP acts via a receptor on the plasma membrane of oocytes. A specific 17 alpha,20 beta-DP receptor has been identified and characterized from defolliculated oocytes of several fish species. The concentrations of 17 alpha,20 beta-DP membrane receptor increase immediately prior to oocyte maturation. The pertussis toxin-sensitive inhibitory G protein is involved in the signal transduction pathway of 17 alpha,20 beta-DP. The early steps following 17 alpha,20 beta-DP action involve the formation of the major mediator of this steroid, maturation-promoting factor, which consists of cdc2 kinase (34 kDa) and cyclin B (46-48 kDa). Immature oocytes contain only monomeric 35 kDa cdc2 and do not stockpile cyclin B, although immature oocytes contain mRNA for cyclin B. 17 alpha,20 beta-DP induces oocytes to synthesize cyclin B, which in turn activates preexisting 35 kDa cdc2 through its threonine 161 phosphorylation by a threonine kinase (M015), producing the 34-kDa active cdc2. 17 alpha,20 beta-DP-induced oocyte maturation is blocked by cordycepin, a polyadenylation inhibitor. Furthermore, cyclin B mRNA was polyadenylated during 17 alpha,20 beta-DP-induced oocyte maturation. These findings suggest that 17 alpha,20 beta-DP initiates translation of cyclin B mRNA through cytoplasmic 3' poly(A) elongation.
Steroids 1997 Jan
PMID:17 alpha,20 beta-dihydroxy-4-pregnen-3-one, a maturation-inducing hormone in fish oocytes: mechanisms of synthesis and action. 902 36

We have previously reported that 5 alpha and 5 beta pathways of steroid metabolism are controlled in vivo by dietary Na+ and glycyrrhetinic acid, see Gorsline et al. 1988; Latif et al. 1990. The present investigations provide evidence supporting the suggestion that endogenous substances may regulate the glucocorticoid inactivating isoenzymes, 11 beta-HSD (hydroxysteroid dehydrogenase) 1 (liver) and 11 beta-HSD2 (kidney). The activity of 11 beta-HSD is impaired in essential hypertension, following licorice ingestion, and in patients with apparent mineralocorticoid excess where 11 beta-HSD2 is particularly affected. In all three conditions, excretion of the less common 5 alpha metabolites is elevated in urine. We now report on the differential abilities of a series of Ring A reduced (5 alpha and 5 beta) adrenocorticosteroid and progesterone metabolites to inhibit these isoenzymes. Using liver microsomes with NADP+ as co-factor (11 beta-HSD1), and sheep kidney microsomes with NAD+ as co-factor (11 beta-HSD2), we have systematically investigated the abilities of a number of adrenocorticosteroids and their derivatives to inhibit the individual isoforms of 11 beta-HSD. A striking feature is the differential sensitivity of the two isoenzymes to inhibition by 5 alpha and 5 beta derivatives. 11 beta-HSD1 is inhibited by both 5 alpha and certain 5 beta derivatives. 11 beta-HSD-2 was selectively inhibited only by 5 alpha derivatives: 5 beta derivatives were without inhibitory activity toward this isoform of 11 beta-HSD. These results indicate the importance of the structural conformation of the A and B Rings in conferring specific inhibitory properties on these compounds. In addition, we discuss the effects of additions or substitutions of other functional groups on the inhibitory potency of these steroid molecules against 11 beta-HSD1 and 11 beta-HSD2.
Steroids 1997 Feb
PMID:Selective inhibition of sheep kidney 11 beta-hydroxysteroid dehydrogenase isoform 2 activity by 5 alpha-reduced (but not 5 beta) derivatives of adrenocorticosteroids. 905 82

11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the enzyme that catalyzes the conversion of biologically active glucocorticoids to their inactive metabolites, was shown to be located exclusively in Leydig cells of the rat testis, and its appearance was associated with the developmental rise in testosterone. Thus, 11 beta-HSD was suggested to play an important role in maintaining steroidogenesis by inactivating excess cortisol that inhibits testosterone production. Whether equivalent protection from glucocorticoids excess is necessary for spermatogenesis is not known, and we have, accordingly, investigated the 11 beta-HSD activity in ejaculated human semen. Both 11 beta-dehydrogenase (11 beta-DH) and 11 beta-oxoreductase (11-OR) activities of 11 beta-HSD were measurable in semen, although seminal plasma was devoid of 11 beta-HSD activity. Azoospermic specimens were associated with low 11 beta-dehydrogenase activity, indicating the presence of enzyme activity in cells other than spermatozoa. Pure spermatozoa separated on percoll gradient could oxidize corticosterone in the presence of NAD or NADP. Significantly higher 11 beta-DH activity is associated with semen specimens with low sperm count (p < .05) and higher level of morphologically abnormal spermatozoa (p < .05). The presence of 11 beta-HSD in human semen and its association with sperm characteristics thus suggests functional role for glucocorticoid exclusion in the sperm maturation process.
Steroids 1997 Mar
PMID:Presence of 11 beta-hydroxysteroid dehydrogenase in human semen: evidence of correlation with semen characteristics. 907 40


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