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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The estrogenic activities of 17beta-estradiol, biphenyl, chlorinated biphenyls, and Aroclor mixtures 1221, 1242, and 1248 were measured with a modified recombinant yeast estrogen assay (i.e., a Saccharomyces cerevisiae-based lac-Z (beta-galactosidase) reporter assay). Modifications of the assay included the use of glass vials instead of plastic microtiter plates and the addition of the medium and yeast before the test substrate. 14C-labeled compounds were used to follow improvements in the assay procedures. 14C-17beta-estradiol recovery from plastic microtiter plates and glass vials using the standard or the modified procedure was approximately 89%. However, 14C-4-CB (4-chlorobiphenyl) recovery was considerably less, ranging from 3% in plastic microtiter plates using the standard procedure to 26% in vials using the modified procedure. These results suggest that the toxicity of strongly hydrophobic chemicals may be underestimated. Using the modified yeast estrogen assay, full agonist activity was observed for 4-CB, 2,4,6-CB, and 2,5-CB while each of the Aroclor mixtures were only partial agonists. The equivalent EC50 values in ppm were in environmentally relevant concentrations for biphenyl (19 ppm), 4-CB (4.5 ppm), 2,5-CB (21 ppm), 2,4,6-CB (0.8 ppm), Aroclor 1221 (2.9 ppm), Aroclor 1242 (0.65 ppm), and Aroclor 1248 (2.3 ppm). Estrogen receptor binding for the individual PCB congeners was 25- to 650-fold less than the reported estrogen binding for the corresponding hydroxylated PCB metabolite. Gas chromatographic/mass spectrometric analysis of yeast extracts indicated that S. cerevisiae hydroxylated the individual PCB congeners in the ppb range. With the exception of biphenyl, the concentration of hydroxylated metabolites obtained from incubation of S. cerevisiae with PCB congeners was consistent with the concentration necessary to elicit a positive estrogen receptor-binding response. This work provides evidence that S. cerevisiae are capable of metabolic transformation of PCBs and that estrogen receptor binding of PCBs is mediated through the hydroxylated metabolite rather than through the direct interaction of the PCB congeners with the estrogen receptor.
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PMID:In vitro estrogen receptor binding of PCBs: measured activity and detection of hydroxylated metabolites in a recombinant yeast assay. 1200 55

Seven reaction products (2-chloro-4-nonylphenol [NP], 2,6-dichloro-4-NP, trichlorophenol, 4-propyl-2'-hydroxyphenol, 4-isobutyl-2'-hydroxyphenol, 4-isoamyl-2'-hydroxyphenol, and 4-isopentyl-2'-hydroxyphenol) were identified by gas chromatography/mass spectrometry (GC/MS) in order to assess the estrogenic activity originated from 4-nonylphenol (4-NP) in drinking water. The estrogenic activities of the aqueous chlorinated 4-NP solution at 10, 60, and 120 min chlorination time were assessed by a yeast two-hybrid system based on the ligand-dependent interaction of two proteins, a human estrogen receptor (ER), and a coactivator. It was found that all three solutions inhibited transcriptional activation induction by 4-NP. Further experiments showed that these solutions also inhibited beta-galactosidase induction by 17beta-estradiol. For the solution at 10 min, the inhibition was found to be due to its toxicity, with an inhibition concentration (IC50) of about 10-fold of concentration of chlorinated 4-NP solution, suggesting the existence of some products with higher yeast toxicity than that of the parent 4-NP. Similar inhibition trends were also found in the dose response of the two solutions at 60 and 120 min, with an IC50 of 10-fold concentration. In these cases, the effects were considered to result from their antagonist action because the two solutions show lower yeast toxicity of which IC50 is 45-fold concentration. This suggests that some products in the chlorinated 4-NP solution elicit the antiestrogenic activities.
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PMID:Products of aqueous chlorination of 4-nonylphenol and their estrogenic activity. 1237 78

This article presents new concepts in affinity chromatography/mass spectrometry for the study of molecular interactions. Chromatographic assays involving estrogen receptor-beta, sorbitol dehydrogenase, human alpha-thrombin, cholera toxin B subunit, beta-galactosidase, and Griffonia simplicifolia isolectin B(4) were established in microaffinity columns and operated in frontal analysis mode. Methods and formalism are presented for the measurement of dissociation constants, using direct methods in which the mass spectrometric signature of the ligand is used to measure breakthrough time and, hence, binding strength. The direct approach is capable of measuring sub-micromolar K(d) and higher, on sub-pmol amounts of immobilized protein, as shown in the cholera toxin assay. Indirect assays that demonstrate the advantage of routine, rugged performance were developed. By tracking the effect of a test ligand on a selected probe, or indicator ligand, dissociation constants in the low nanomolar range could be reliably determined for ligands to estrogen receptor-beta. Mass spectrometry supports the resolution of complex ligand mixtures, and it is demonstrated in the sorbitol dehydrogenase assay that ligands can be rank ordered across approximately three orders of magnitude in K(d), in a single run. A new concept for rapid mixture prescreening is presented, in which an indicator ligand can be used to discriminate between mixtures that contain high levels of weak ligands and those that contain single strong ligands.
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PMID:Frontal affinity chromatography-mass spectrometry assay technology for multiple stages of drug discovery: applications of a chromatographic biosensor. 1284 1

The hypothesis that cross-talk between membrane-active beta-adrenergic agonists and estrogens includes beta-adrenergic modulation of estrogen receptor (ER)-regulated gene expression was investigated. Vascular smooth muscle-derived A7r5 cells were transfected with an ERalpha expression plasmid (pCR3.1-hERalpha), the estrogen response element (ERE)-linked reporter pERE-E1b-luciferase (ERE-Luc), and pCMV-beta-galactosidase using a lysine-conjugated adenovirus transfection method. Hormone or agonist treatment and harvest followed 6 hours and 24 hours later, respectively. Treatment with 17beta-estradiol (E(2), 1 nmol/L) significantly stimulated ERE-Luc activity. Isoproterenol (10-9 to 10-6 mol/L) treatment alone did not stimulate ERE-Luc activity. Cotreatment with both E(2) and isoproterenol resulted in complete inhibition of E(2)-stimulated ERE-Luc activity. This isoproterenol effect was prevented by the beta-adrenergic antagonist propanolol (10-6 mol/L). Adrenomedullin treatment in these cells (1-50 nmol/L) did not inhibit ER/ERE-Luc activity, whether in the presence or absence of E(2). Moreover, isoproterenol did not affect vitamin D-stimulated VDRE-Luc expression, indicating that the inhibitory effect of isoproterenol on E(2)-directed ERE-Luc expression is specific among nuclear transcription factor receptors. Moreover, in MCF-7 breast cancer cells, there was no effect of isoproterenol on ER/ERE-directed transcription in the absence or presence of E(2), demonstrating tissue specificity of this isoproterenol effect. These studies demonstrate cross-talk between the beta-adrenergic agonist isoproterenol and ER-directed reporter gene expression in A7r5 cells. Furthermore, this cross-talk is specific with respect to agonist, nuclear receptor species, and cell type. These observations may have important implications both for the use of beta-adrenergic agents to treat hypertension and for possible gender-related differences in cardiovascular regulation.
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PMID:Cross-talk between beta-adrenergic stimulation and estrogen receptors: isoproterenol inhibits 17beta-estradiol-induced gene transcription in A7r5 cells. 1288 32

The syntheses and characterization of bisphenol A mono- and di-beta-D-glucopyranosides were undertaken to confirm that these compounds are major plant metabolities of bisphenol A (BPA) and to allow an assessment of their estrogenicity. Synthesis involved the glucosidation of unprotected BPA with glucose penta-acetate with phosphorus oxychloride as catalyst. The estrogenic activity of BPA and its mono- and di-beta-D-glucopyranosides were measured with an enzyme-linked immunosorbent assay (ELISA)-based estrogen receptor competitive binding assay and with a yeast two-hybrid assay adapted to a chemiluminescent reporter gene (for beta-galactosidase). Both methods showed that the estrogenicity of BPA was eliminated by formation of the di-glucoside, but whereas the ELISA-based method indicated that reduced activity remained in the monoglucoside, the yeast two-hybrid method showed the monoglucoside to be inactive. Presumably these results reflect the more complex interactions of test compound and cellular components required to demonstrate estrogenicity in the yeast two-hybrid assay. As these processes parallel those in mammalian cells, the yeast two-hybrid method is likely to be the more realistic assay. The uptake and metabolism of BPA by plants offers the possibility of phytoremediation of contaminated water, but also provides an additional route for the compound to enter the human food chain.
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PMID:Synthesis and estrogenic activity of bisphenol a mono- and di-beta-D-glucopyranosides, plant metabolites of bisphenol A. 1455 89

Tamoxifen has contributed to a dramatic reduction in breast cancer mortality and recent results indicate that aromatase inhibitors may further improve survival in some patients. Nevertheless, a substantial proportion of patients become resistant to treatment. To date, with the exception of estrogen receptor (ER) determination by ligand binding or immunohistochemical techniques, there has been no way of predicting which of several therapies is indicated in particular patients. We describe a novel assay using the adenoviral gene delivery system to assess ER function in breast cancer cells derived directly from patients. The purification and short-term culture of these cells has been recently described by our laboratory. Adenovirus containing an estrogen-regulated beta-galactosidase reporter gene (ERE-lacZ) was constructed and used to test ER activity in breast cancer cells derived from 18 patients with primary and 16 patients with metastatic cancer, under varying treatment schedules. The adenoviral assay enabled ER activity to be readily determined in purified cells from primary breast cancers and secondary sites. Breast cancers cells could be categorized on the basis of ER activity in the absence of ligand, the presence of estrogen or anti-estrogens. In primary breast cancers, our results correlated with ER determination by immunohistochemistry in 78% of cases. In patients who had become resistant to tamoxifen, however, we found some in whom reporter activity was stimulated by tamoxifen and others whose tumors were either still estrogen responsive or completely unresponsive, irrespective of the original ER content. Our findings indicate that this reporter assay could be useful in decisions regarding use of adjuvant endocrine therapies in breast cancer.
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PMID:Reporter gene assay demonstrates functional differences in estrogen receptor activity in purified breast cancer cells: a pilot study. 1456 18

An application of gas sensors for rapid bioanalysis is presented. An array of temperature-modulated semiconductor sensors was used to characterize the headspace above a cell culture. Recombinant Saccharomyces cerevisiae yeast cells, able to respond to 17 beta-estradiol by producing a reporter protein, were used as a model system. Yeast cells had the DNA sequence of the human estrogen receptor stably integrated into the genome, and contained expression plasmids carrying estrogen-responsive sequences and the reporter gene lac-Z, encoding the enzyme beta-galactosidase. The sensor-response profiles showed small but noticeable discrimination between cell samples induced with 17 beta-estradiol and non-induced cell samples. The sensor array was capable of detecting changes in the volatile organic compound composition of the headspace above the cultured cells, which can be associated with metabolic changes induced by a chemical compound. This finding suggests the possibility of using cross-selective gas-sensor arrays for analysis of drugs or bioactive molecules through their interaction with cell systems, with the advantage of providing information on their bioavailability.
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PMID:Use of a gas-sensor array for detecting volatile organic compounds (VOC) in chemically induced cells. 1461 63

To assess the estrogenic activity potentially stemming from 17beta-estradiol (E2) in drinking water, ESI-LC-MS was used to identifythe products of its aqueous chlorination under the following conditions: 50 microg/L E2, 1.46 mg/L sodium hypochlorite, pH 7.5, 25 degrees C. Seven products, including 2,4-dichloro-17beta-estradiol, monochloroestrone, 2,4-dichloroestrone, and the four byproducts such as 4-[2-(2,6-dichloro-3-hydroxyphenyl)ethyl]-7alpha-methyloctahydroinden-5-one (product C in the text) were identified in chlorinated E2 solution. The estrogenic activities of the aqueous chlorinated E2 solution at 10, 30, 60, 120, and 180 min contact time were assessed by a yeast two-hybrid system based on the ligand-dependent interaction of two proteins, a human estrogen receptor (ER) and a coactivator. All five solutions elicited transcriptional activation induction. The maximal beta-galactosidase activities induced by the chlorinated solution at 10, 30, and 60 min were similar and slightly lower than those before chlorination, while the activities of the chlorinated solution at 120 and 180 min were about 40% of those before chlorination. Finally, 4-chloro-17beta-estradiol (4-chloro-E2) (we failed to synthesize the 2-chloroestrone (2-chloro-E1)), 2,4-dichloro-17beta-estradiol (2,4-dichloro-E2), and 2,4-dichloroestrone (2,4-dichloro-E1) were synthesized, and product C was fractionated by HPLC. It was found that 4-chloro-E2 elicited strong estrogenic activity, at almost the same level as that of estrone (EC50 = 10(2) nM), while 2,4-dichloro-E2 elicited weaker beta-galactosidase activity compared with that of 4-chloro-E2. The EC50 was ca. 10(3) nM. The maximal beta-galactosidase activity for 2,4-dichloro-E1 was lower than that of 2,4-dichloro-E2, while its EC50 was similar to that of 2,4-dichloro-E2. In addition, product C, 4-[2-(2,6-dichloro-3-hydroxyphenyl)ethyl]-7alpha-methyloctahydroinden-5-one, induced high beta-galactosidase activity at the relatively higher concentration of 3.5 x 10(5) nM. On the basis of the dose-response curve of a single byproduct of chlorinated E2, the estrogenic activity at 120 and 180 min appears to be induced mainly by 2,4-dichloro-E2 and 2,4-dichloro-E1.
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PMID:Products of aqueous chlorination of 17beta-estradiol and their estrogenic activities. 1471 78

The skeleton supports body structures in vertebrates and helps maintain calcium homeostasis throughout life. Disruption of genes involved in mammalian bone formation has often led to embryonic lethality, hence preventing study of these genes' role in adult animals. To develop a usable tool for such study, we generated transgenic mice in which a 2.3-kb mouse Col1a1 proximal promoter, which is active in all osteoblasts, drives a transgene coding for a polypeptide consisting of Cre recombinase fused to a mutated ligand-binding domain of the estrogen receptor. In this Col1a1-CreERT2 mouse line, expression patterns of the transgene and of the resulting Cre-mediated DNA recombination are analyzed by crossing with ROSA26 reporter mice and by measurement of beta-galactosidase activity and X-gal staining. Exposure to 4-hydroxytamoxifen induced Cre-mediated recombination in osteoblasts in virtually all bones and in odontoblasts in teeth of both embryos and postnatal mice. The generation of these transgenic mice provides a new and important tool with which to study the function of specific genes in bone and tooth physiology and diseases in intact animals after birth.
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PMID:Transgenic mice expressing a ligand-inducible cre recombinase in osteoblasts and odontoblasts: a new tool to examine physiology and disease of postnatal bone and tooth. 1557 32

Using a fluorescein di-beta-D-galactopyranoside (FDG) substrate we show that in live cells of an estrogen-sensitive yeast strain RMY/ER-ERE with human estrogen receptor (ERalpha) gene and the lacZ gene which encodes beta-galactosidase, the uptake of 17beta-estradiol (E2) and the subsequent production of beta-galactosidase enzyme occur quite rapidly, with maximal enzyme-catalyzed product formation evident after about 30 min of exposure to E2. This finding which agrees with the well-known rates of enzyme-catalyzed reactions could have implications for shortening the duration of environmental sample screening and monitoring regimes using yeast-based estrogen assays, and the development of biosensors for environmental estrogens to complement quantification methods.
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PMID:Developing a biosensor for estrogens in water samples: study of the real-time response of live cells of the estrogen-sensitive yeast strain RMY/ER-ERE using fluorescence microscopy. 1614 3


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