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)

7 beta-Hydroxysteroid dehydrogenase (7 beta-HSD) was produced by Ruminococcus sp. PO1-3 obtained from among human intestinal bacteria. The enzyme was purified from a crude extract by ammonium sulfate fractionation, and Butyl-Toyopearl 650M, Sephadex G-150, Matrex Red A and Octyl-Sepharose chromatographies. The purified enzyme was obtained as a single band on polyacrylamide gel electrophoresis with enzyme activity staining and as one band corresponding to a molecular weight of 30,000 on SDS-polyacrylamide gel electrophoresis. On gel filtration, its apparent molecular weight was estimated to be 60,000. The enzyme had a sulfhydryl group(s) in its active site. Substrate specificity studies revealed that the enzyme showed absolute specificity for the beta-configuration of a hydroxyl group at the 7 position of bile acids, and required NADP+ and NADPH as cosubstrates. The Km values for ursodeoxycholic acid, 7-k etolithocholic acid, NADP+, and NADPH were 5.0, 8.5, 7.7, and 24 microM, respectively.
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PMID:Purification and characterization of 7 beta-hydroxysteroid dehydrogenase from Ruminococcus sp. of human intestine. 348 Aug 90

Improved purification schemes are reported for the enzymes L-aspartase and aspartokinase-homoserine dehydrogenase I from Escherichia coli. Dye-ligand chromatography on commercially available dye matrices are incorporated as key steps in these purifications. Red A-agarose has a high affinity for L-aspartase, which is then eluted as a homogeneous protein fraction with 1 mM L-aspartic acid. Green A-agarose shows a high binding affinity for the bifunctional enzyme aspartokinase-homoserine dehydrogenase I. Purification is accomplished by elution with NADP+, followed by formation of a ternary complex with NADP and cysteine, a good competitive inhibitor of the homoserine dehydrogenase activity, and rechromatography on Green A-agarose. The final specific activity of each purified enzyme equaled or exceeded previously reported values, the overall yield of enzymes obtained was significantly higher, and these improved purification schemes were found to be more amenable to being scaled up for the production of large quantities of purified enzyme.
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PMID:Purification of aspartase and aspartokinase-homoserine dehydrogenase I from Escherichia coli by dye-ligand chromatography. 389 16

The five enzymes responsible for the conversion of L-aspartate to L-threonine in Escherichia coli were purified to homogeneity and subsequently reconstituted in vitro in ratios approximating those found in vivo. 31P NMR was used to conveniently monitor the rates of consumption of the substrates ATP and NADPH, the accumulation of the intermediates beta-aspartyl phosphate and homoserine phosphate, and the formation of the products ADP, NADP+, and Pi in a single experiment. By this method, the flux of aspartic acid through the enzymes of the pathway was monitored in the absence and in the presence of several alternative substrates and inhibitors. Several known antimetabolites were found to be alternative substrates that ultimately became inhibitors of pathway flux. L-threo-3-Hydroxyaspartic acid was converted to 3-hydroxyhomoserine phosphate by the first four enzymes of the pathway. The antimetabolite L-threo-3-hydroxyhomoserine was found to bind to and inhibit aspartokinase-homoserine dehydrogenase I in a cooperative fashion (I 0.5 = 3 mM, nH = 2.5), similar to the action of the allosteric end product inhibitor L-threonine (I 0.5 = 0.36 mM, nH = 2.4). In the presence of the remaining enzymes of the pathway, however, L-threo-3-hydroxyhomoserine was phosphorylated to the apparent ultimate antimetabolite L-threo-3-hydroxyhomoserine phosphate that was a potent inhibitor of threonine synthase and consequently of L-threonine biosynthesis. When aspartic acid alone was examined as a substrate of the enzymes of the pathway, no accumulation of the beta-aspartyl phosphate and homoserine phosphate intermediates was observed. However, in the presence of either 5 mM L-threo-3-hydroxyhomoserine or 5 mM L-threo-3-hydroxyhomoserine phosphate, homoserine phosphate was found to accumulate. In contrast to the homoserine phosphate and 3-hydroxyhomoserine phosphate intermediates, both of which were very stable, the acylphosphate intermediates beta-aspartyl phosphate and beta-3-hydroxyaspartyl phosphate were highly susceptible to hydrolysis, with first-order rate constants of 4.6 X 10(-3) min-1 and 4.5 X 10(-2) min-1 (pH 7.8, 25 degrees C), respectively.
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PMID:Interaction of aspartate and aspartate-derived antimetabolites with the enzymes of the threonine biosynthetic pathway of Escherichia coli. 615 Sep 34

Detailed histochemical localization of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and 17 beta-HSD was made in the goat testis using both NAD and NADP coenzymes. The substrates used for 3 beta-HSD were dehydroepiandrosterone (DHA) and pregnenolone whereas 17 beta-HSD was localized with testosterone and oestradiol. In general, the activity of the enzymes varied with the cell type, substrate and coenzyme. In seminiferous tubules, DHA and NAD were the preferred substrate and coenzyme respectively for 3 beta-HSD. In addition, in interstitial tissue, NAD was the preferred coenzyme with DHA whereas no such preference existed with pregnenolone. 17 beta-Hydroxysteroid dehydrogenase showed a similar pattern in the two main compartments of the testis, as testosterone and oestradiol were equally utilized and NAD was the preferred coenzyme in both these compartments. The activities of the enzymes increased during the process of spermiogenesis and were higher in seminiferous tubules than in interstitial tissue, especially in elongated spermatids and spermatozoa.
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PMID:Histochemical studies on steroid dehydrogenases in the testis of the goat (Capra hircus). 632 73

Homoserine dehydrogenase in dialyzed cell extracts of Bacillus subtilis 168 was studied, particularly with regard to inhibition, repression, and level of activity as a function of stage of development (growth and sporulation). It was assayed in the "forward direction" using L-aspartic semialdehyde and NADPH as substrates. Of the potentials inhibitors tested, only cysteine and NADP were found to be effective. Both L- and D-cysteine were equally effective. Therefore, the physiological significance of cysteine as an inhibitor is somewhat questionable. Amino acids involved in repression of homoserine dehydrogenase included methionine, isoleucine, possibly threonine, and one or more unidentified components of Casamino acids. The specific activity of homoserine dehydrogenase was highest during the exponential phase of growth and declined steadily during the stationary phase of growth. The low specific activity during late sporulation may favor preferential funnelling of L-aspartic semialdehyde into the lysine pathway, where it is needed for synthesis of large amounts of dipicolinic acid and diaminopimelic acid.
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PMID:Sporulation and regulation of homoserine dehydrogenase in Bacillus subtilis. 678 15

Cortisol:cortisone interconversion was studied in human decidua obtained from three groups of patients at term (37-42 weeks): before the onset of labour (at elective Caesarean section), after labour of spontaneous onset, and after labour of induced onset. When intact tissue was incubated with [3H]cortisol or [3H]cortisone in phosphate buffer without added substrate or cofactors, cortisone to cortisol was the dominant conversion. However, when damaged cells or tissue homogenates were used in the same conditions, the dominant direction of the reaction was reversed, with a large increase in oxidative (cortisol to cortisone) activity. Cortisol:cortisone interconversion was similar in the three groups of samples using either intact tissue or homogenates, as was the total 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) activity measured in tissue homogenates in the presence of added substrate (cortisol or cortisone) and cofactors (NADP+ or NADPH). Endogenous cortisol concentrations in decidua were higher than those of cortisone, and the ratio of cortisol to cortisone was similar in the three groups. These findings suggest that there are no changes in human decidual 11 beta-HSD activity in relation to parturition. Specific activity of 11 beta-HSD decreased at high protein concentrations, suggesting the presence of some enzyme inhibitor(s) in homogenized decidual tissue.
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PMID:Cortisol:cortisone interconversion by human decidua in relation to parturition: effect of tissue manipulation on 11 beta-hydroxysteroid dehydrogenase activity. 695 60

A quantitative cytochemical method for the demonstration of 20 alpha-hydroxysteroid dehydrogenase activity (20 alpha-HSD) in the regressing corpora lutea of the adult rat ovary is described. The method employs unfixed tissue sections and relies upon the oxidation of 20 alpha-hydroxy-4-pregnen-3-one (20 alpha-OH-P) with nitro blue tetrazolium as the hydrogen acceptor. The enzyme was dependent upon NADP+ for its activity and was inactive when 20 beta-hydroxy-4-pregnen-3-one (20 beta-OH-P) was used as a substrate. The apparent Km values for 20 alpha-OH-P and NADP+ were 3 x 10(-4) M and 2.5 x 10(-5) M respectively. Inhibition of 20 alpha-HSD activity by steroids was demonstrable at pH 8. Androstenedione was by far the most potent inhibitor, followed by progesterone (the product of the enzyme activity) 17 alpha-hydroxyprogesterone, Compound S and 20 beta-OH-P. At pH 6.8, a pH more favourable to the progesterone leads to 20 alpha-OH-P reaction, only progesterone and 17 alpha-hydroxyprogesterone were inhibitory. Testosterone was without demonstrable effect at either pH.
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PMID:20 alpha-Hydroxysteroid dehydrogenase activity in the rat corpus luteum; a quantitative cytochemical study. 695 73

A partial characterization of human term placental 3 beta-HSDH in mitochondria is reported. Apparent KM of pregnenolone: 70 nM. A dose-dependent stimulation of 3 beta-HSDH by NAD+ or NADP+ was observed in the range from 10(-6) to 10(-3) M (KM value of NAD+: 20 microM). At equimolar concentrations NAD+ is more than 10-fold as effective a cofactor of the 3 beta-HSDH than NADP+. pH optimum: 9.5 (glycine-NaOH buffer). Temperature optimum 40-45 degrees C. A rapid loss of 3 beta-HSDH activity was found after preincubation of the enzyme at 37 degrees C after 30 min; less than 50% of initial enzyme activity is present. No inhibition was obtained by Mg2+, Ca2+ Sr2+ and Ba2+ (1-100 mM). A strong inhibition was achieved with 1 mM Zn2+, Cd2+, Cu2+ and 10 mM and 100 mM Fe2+, Mn2+, Co2+ and Ni2+.
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PMID:Partial characterization of placental 3 beta-hydroxysteroid dehydrogenase (EC 1.1.1.145), delta 4-5isomerase (EC 5.3.3.1) in human term placental mitochondria. 695 97

The formation of spironolactone (S) bodies, eosinophilic laminated cytoplasmic inclusions, is induced in the aldosterone-producing cells of the human adrenal cortex after the administration of spironolactone. The aim of this study was to define the enzyme histochemical characteristics of S bodies, S-body-containing cells, and the apparently hyperplastic zona glomerulosa (zG) of adrenal tissues attached to aldosteronomas. S bodies were found in 14 of 19 aldosteronomas, in 10 of 19 adrenal tissues attached to aldosteronomas, and in the adrenal tissues in a patient with aldosteronism due to bilateral diffuse zG hyperplasia. The S bodies themselves exhibited most intense 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) activity but did not exhibit glucose-6-phosphate dehydrogenase (G6PD), NADP-dependent isocitrate dehydrogenase (NADP-ICDH), or succinate dehydrogenase (SDH) activity, confirming histochemically the origin of S bodies in the smooth endoplasmic reticulum. In two adenomas, S bodies were found to be surrounded by reaction products of acid hydrolase but were not found in the other adenomas and the remaining adrenal tissues. S-body-containing cells, irrespective of being neoplastic or not, showed enhanced 3 beta HSD, G6PD, and NADP-ICDH activity and weak SDH activity (Type I pattern of enzyme activity). Though zG was hyperplastic in most of the adrenal tissues attached to the adenomas, zG cells that did not contain S bodies showed the opposite pattern (Type II pattern) of enzyme activity (ie, weak 3 beta HSD, G6PD, and NADP-ICDH activity and intense SDH activity), in contrast to those in the adrenal tissues in a patient with aldosteronism due to bilateral diffuse zG hyperplasia (which showed the Type I pattern). The results are consistent with the view that hyperplastic zG cells, except S-body-containing cells, in the case of aldosteronoma are not hyperfunctioning. The latter cells may have enhanced but possibly abortive steroidogenic activity.
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PMID:Spironolactone bodies in aldosteronomas and in the attached adrenals. Enzyme histochemical study of 19 cases of primary aldosteronism and a case of aldosteronism due to bilateral diffuse hyperplasia of the zona glomerulosa. 719 52

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) is a microsomal enzyme complex responsible for the interconversion of active 11-hydroxy glucocorticoids to inactive 11-oxo metabolites. It has long been controversially discussed whether 11-dehydrogenation and 11-oxoreduction are catalysed by a single bidirectional enzyme or if the 11 beta-HSD system comprises 2 kinetically distinct microsomal enzyme activities, 11-dehydrogenase and 11-oxoreductase. However, 11-oxoreduction of homogeneously purified 11 beta-HSD could not be demonstrated under in vitro conditions until today. We have purified 11 beta-HSD from mouse liver microsomes to homogeneity by a purification method which affords a gentle membrane protein solubilization as well as providing a favourable detergent surrounding during the various chromatographic steps. Following 11-dehydrogenation of corticosterone and 11-oxoreduction of dehydrocorticosterone simultaneously throughout the entire purification procedure we could demonstrate that 11 beta-HSD retains both oxidative and reductive activities in almost the same ratio, which is also true for the homogeneously purified enzyme. Deducing from the coincidentally increasing specific activities of 11-dehydrogenation and 11-oxoreduction the conclusion can be drawn that both activities reside within the same protein. Furthermore, in addition to NADP(H) also NAD(H) can serve as cosubstrate, which is mainly true for the oxidative direction. In conclusion, our results provide evidence that the oxidative and reductive behaviour of 11 beta-HSD can be explained by the concept of a unique, reversible oxidoreductase thus disproving the two enzyme theory.
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PMID:The purification of 11 beta-hydroxysteroid dehydrogenase from mouse liver microsomes. 751 8


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