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

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enzymatic sulfation has been implicated to play a key role in a number of essential biological pathways including xenobiotic detoxication, carcinogen activation, and the regulation of intra-tissue hormone activity. In order to increase our understanding of the critical determinants governing the regulation of sulfotransferase gene expression, we investigated age-, gender-, and xenobiotic-related alterations in hydroxysteroid sulfotransferase-a or aryl sulfotransferase-IV gene expression. Northern blot and slot blot analyses showed that rat hepatic hydroxysteroid sulfotransferase-a mRNA expression was responsive to age- and gender-related signals. The results also suggested that the rat hepatic aryl sulfotransferase-IV and hydroxysteroid sulfotransferase-a genes are differentially regulated. Northern blot and reverse transcriptase polymerase chain reaction analyses demonstrated that hydroxysteroid sulfotransferase-a mRNA was expressed to a greater extent in female rat liver than in lung or kidney tissue. In addition, rat hepatic hydroxysteroid sulfotransferase-a gene expression in mature female rats, although not substantially altered in response to short-term fasting or high-dose dexamethasone treatment, was suppressed after treatment with the polycyclic aromatic hydrocarbon, 3-methylcholanthrene.
...
PMID:Sulfotransferase gene expression in rat hepatic and extrahepatic tissues. 803 71

Heparan-sulfate 2-sulfotransferase (HS2ST), which catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to L-iduronic acid at position 2 in heparan sulfate, was purified from cultured Chinese hamster ovary (CHO) cells to apparent homogeneity (Kobayashi, M., Habuchi, H., Habuchi, O., Saito, M., and Kimata, K. (1996) J. Biol. Chem. 271, 7645-7653). The internal amino acid sequences were obtained from the peptides after digestion of the purified protein with a combination of endoproteinases. Mixed oligonucleotides based on the peptide sequences were used as primers to obtain a probe fragment by reverse transcriptase-polymerase chain reaction using CHO cell poly(A)+ RNA as template. The clone obtained from a CHO cDNA library by screening with the probe is 2.2 kilobases in size and contains an open reading frame of 1068 bases encoding a new protein composed of 356 amino acid residues. The protein predicts a type II transmembrane topology similar to other Golgi membrane proteins. Messages of 5.0 and 3.0 kilobases were observed in Northern analysis. Evidence that the cDNA clone corresponds to the purified HS2ST protein is as follows. (a) The predicted amino acid sequence contains all five peptides obtained after endoproteinase digestion of the purified protein; (b) the characteristics of the predicted protein fit those of the purified protein in terms of molecular mass, membrane localization, and N-glycosylation; and (c) when the cDNA containing the entire coding sequence of the enzyme in a eukaryotic expression vector was transfected into COS-7 cells, the HS2ST activity increased 2.6-fold over controls, and the FLAG-HS2ST fusion protein purified by affinity chromatography showed the HS2ST activity alone.
...
PMID:Molecular cloning and expression of Chinese hamster ovary cell heparan-sulfate 2-sulfotransferase. 915 62

Heparan-sulfate 6-sulfotransferase (HS6ST) catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 6 of the N-sulfoglucosamine residue of heparan sulfate. The enzyme was purified to apparent homogeneity from the serum-free culture medium of Chinese hamster ovary (CHO) cells (Habuchi, H., Habuchi, O., and Kimata, K. (1995) J. Biol Chem. 270, 4172-4179). From the amino acid sequence data of the purified enzyme, degenerate oligonucleotides were designed and used as primers for the reverse transcriptase-polymerase chain reaction using poly(A)+ RNA from CHO cells as a template. The amplified cDNA fragment was then used as a probe to screen a cDNA library of CHO cells. The cDNA clone thus obtained encoded a partial peptide sequence composed of 236 amino acid residues that included the sequences of six peptides obtained after endoproteinase digestion of the purified enzyme. This cDNA clone was applied to the screening of a human fetal brain cDNA library by cross-hybridization. The isolated cDNA clones contained a whole open reading frame that predicts a type II transmembrane protein composed of 401 amino acid residues. No significant amino acid sequence identity to any other proteins, including heparan-sulfate 2-sulfotransferases, was observed. When the cDNA for the entire coding sequence of the protein was inserted into a eukaryotic expression vector and transfected into COS-7 cells, the HS6ST activity increased 7-fold over the control. The FLAG fusion protein purified by anti-FLAG affinity chromatography showed the HS6ST activity alone. Northern blot analysis revealed the occurrence of a single transcript of 3.9 kilobases in both human fetal brain and CHO cells. The results, together with the ones from our recent cDNA analysis of heparan-sulfate 2-sulfotransferase (Kobayashi, M., Habuchi, H., Yoneda, M., Habuchi, O., and Kimata, K. (1997) J. Biol. Chem. 272, 13980-13985), suggest that at least two different gene products are responsible for 6- and 2-O-sulfations of heparan sulfate.
...
PMID:Molecular characterization and expression of heparan-sulfate 6-sulfotransferase. Complete cDNA cloning in human and partial cloning in Chinese hamster ovary cells. 953 12

A mouse liver homogenate was shown to contain enzymatic activities catalyzing the sulfation of 3,4-dihydroxyphenylalanine (Dopa) and tyrosine isomers with a pH optimum of 8.25. Western blot analysis revealed a 34 kDa protein exhibiting immunologic cross-reactivity to antiserum against rat liver SULT1B1 sulfotransferase. By employing the reverse transcriptase-polymerase chain reaction (RT-PCR) technique, a 910-base pair product encoding the putative mouse liver SULT1B1 sulfotransferase was obtained. Using this PCR product as a probe, a cDNA containing the entire open reading frame of the mouse liver SULT1B1 sulfotransferase was cloned from a mouse liver Lambda ZAP cDNA library. The nucleotide sequence indicated it is a new enzyme. The deduced amino acid sequence exhibited 87.6, 72.3, 55.9, 54.2, 52.8, 51.1, and 49.4% identity to the amino acid sequences of the rat liver SULT1B1 sulfotransferase, human thyroid hormone sulfotransferase, mouse phenol sulfotransferase, rat liver phenol sulfotransferase, rat liver hydroxyarylamine sulfotransferase, mouse estrogen sulfotransferase, and rat estrogen sulfotransferase. Upon transfection of COS-7 cells with an expression vector (pcDNA3) harboring the cDNA encoding this new enzyme, a 34 kDa protein exhibiting immunologic cross-reactivity to antiserum against the rat liver SULT1B1 sulfotransferase was expressed. The recombinant sulfotransferase exhibited enzymatic activities toward Dopa and tyrosine isomers, as well as dopamine and 3,3',5-triiodo-L-thyronine. Northern blot analyses indicated the SULT1B1 sulfotransferase was predominantly expressed in liver, but not in the other ten mouse organs examined. Furthermore, the enzyme was found to be expressed in a developmental stage-dependent manner, being at a very low level in liver samples from 1-day-old mice and then gradually increasing to the maximum level in liver samples from 4-week-old mice.
...
PMID:Molecular cloning, expression, and characterization of a novel mouse liver SULT1B1 sulfotransferase. 964 46

Using reverse transcriptase-polymerase chain reaction amplification it was possible to detect the presence of type 1 human estrogen sulfotransferase (hEST1) mRNA in the hormone-dependent: MCF-7 and T-47D, and hormone-independent: MDA-MB-231 and MDA-MB-468, human breast cancer cells. The expression of this mRNA is significantly higher in the MDA-MB-468 cells and a correlation of this mRNA expression with the enzymatic activity was observed. The progestin promegestone (R-5020) at a low concentration (5 x 10(-7) M) can significantly increase the estrogen sulfotransferase activity and its mRNA in the hormone-dependent MCF-7 and T-47D cells. As estrogen sulfates are biologically inactive, the stimulatory effect on sulfotransferase by promegestone may open attractive possibilities in the control of estradiol in human breast cancer.
...
PMID:Human estrogen sulfotransferase (hEST1) activities and its mRNA in various breast cancer cell lines. Effect of the progestin, promegestone (R-5020). 974 35

The induction of cytochrome P450 (CYP450) and Phase II conjugating enzymes by prototypical hepatic enzyme inducers was studied in adult male rat hepatocytes. Hepatocytes were suspended and cultured in diluted Matrigel in a basal serum-free Dulbecco's modified Eagle medium and exposed to the prototypical liver enzyme inducers, 3-methylcholanthrene, phenobarbital, hydrocortisone, and clofibrate for 48 h. Total RNA and microsomes were isolated and prepared, respectively, at 72 h. The expression of CYP1A1, CYP1A2, CYP2B1, CYP2C11, CYP2E1, CYP3A1, CYP3A2, CYP4A1, fatty acyl-CoA oxidase, uridine diphosphate-glucuronosyltransferase, glutathione-S-transferase, and sulfotransferase was determined at the mRNA level with reverse transcriptase polymerase chain reaction (RT-PCR). The expression of CYP1A1, CYP2B1, CYP2C11, CYP2E1, and CYP4A1 was also measured at the apoprotein level by Western immunoblotting. Using these culture and expression analysis techniques, we have found that the expression of these metabolic enzymes can be maintained in culture for up to 7 d at the mRNA and apoprotein levels. In addition, hepatocytes were found to respond to chemical enzyme inducers with marked increases in enzyme expression at either the mRNA or protein level and in a concentration-related fashion. Cells were responsive to enzyme induction as early as 24 h after initial plating. The results obtained from this investigation indicate that the presence of diluted Matrigel (at a concentration of 0.35 mg/ml), the use of low concentrations of insulin (1 microM), hydrocortisone (0.1 microM), and serum-free culture medium can maintain the differentiated phenotype and responsiveness of cultured hepatocytes to chemical-induced metabolic enzyme expression. Under the conditions used in this study, enzyme induction in adult male rat hepatocytes shows close agreement with enzyme induction observed in the livers of rats exposed to these or similar prototypical enzyme inducers. Rat hepatocytes cultured in the presence of diluted Matrigel coupled with enzyme mRNA expression analysis with RT-PCR are proven to be a valuable and important in vitro toxicological approach to assess the chemical-induced changes in expression of liver CYP450 and Phase II conjugating enzymes.
...
PMID:Analysis of cytochrome P450 and phase II conjugating enzyme expression in adult male rat hepatocytes. 1047 7

We examined the pharmacokinetics and metabolism of the experimental nucleoside reverse transcriptase inhibitor compound stampidine in mice, dogs, and cats. Also reported is the identification of p-bromophenyl sulfate (p-Br-Ph-S) as a major in vivo phase II metabolite of stampidine. Liver cytosol was shown to take part in the hydrolysis of stampidine to form alaninyl-STV-monophosphate (Ala-STV-MP), 2',3'-didehydro-3'-deoxythymidine (STV), and p-bromophenol; p-bromophenol was further sulfonated by sulfotransferase to form p-Br-Ph-S. Notably, plasma concentrations of stampidine >4 logs higher than its IC(50) value can be achieved in both dogs and cats after its p.o administration at a 100-mg/kg dose level. In dogs as well as cats, stampidine was metabolized to yield micromolar concentrations of the active metabolites ala-STV-MP and STV, which is similar to the metabolism of stampidine in mice. These findings encourage the further development of this new antiviral agent for possible clinical use in human immunodeficiency virus-infected patients.
...
PMID:Metabolism of stavudine-5'-[p-bromophenyl methoxyalaninyl phosphate], stampidine, in mice, dogs, and cats. 1243 28

Using the reverse transcriptase-polymerase chain reaction technique, a full-length cDNA encoding a novel zebrafish sulfotransferase was cloned and sequenced. Sequence analysis indicated that this zebrafish sulfotransferase belongs to the SULT1 cytosolic sulfotransferase gene family. The recombinant form of the zebrafish sulfotransferase, purified from Escherichia coli cells, displayed sulfating activities toward a number of endogenous compounds, in particular dopamine and thyroid hormones, in addition to xenobiotics including some flavonoids, isoflavonoids, and other phenolic compounds. The zebrafish sulfotransferase exhibited substrate dependence in pH optimum. In comparison with those determined with dopamine as substrate, the zebrafish sulfotransferase displayed much lower K(m) and higher V(max) with n-propyl gallate as substrate. A thermostability experiment revealed the enzyme to be relatively stable over a temperature range between 20 and 43 degrees C. Among 10 divalent metal cations tested, Hg(2+), Co(2+), Zn(2+), Cd(2+), Cu(2+), and Pb(2+) exhibited dramatic inhibitory effects on the activity of the zebrafish sulfotransferase.
...
PMID:cDNA cloning, expression, and functional characterization of a zebrafish SULT1 cytosolic sulfotransferase. 1274 56

Expression analysis by reverse transcriptase (RT)-PCR indicates that human adipose tissue is not likely to perform de novo synthesis of steroid hormones from cholesterol because the mRNAs of cytochromes P450scc and P450c17, and of the steroidogenic-related proteins, steroidogenic acute regulatory protein and steroidogenic factor 1, were not detected. Instead, our data support an intracrine role of adipose tissue, in which adrenal dehydroepiandrosterone sulfate (DHEA-S), the most abundant circulating androgen in man, is selectively uptaken, desulfated, and converted into bioactive androgens and estrogens. Three organic anion-transporting polypeptides-B, -D, and -E, presumably involved in DHEA-S transmembrane transport, were demonstrated at the mRNA level. While sulfotransferase expression was not found, the occurrence of steroid sulfatase (STS), converting DHEA-S to DHEA, was established at the mRNA, protein and catalytic activity levels. The 5'-rapid amplification of cDNA ends analysis showed that STS transcription in adipose tissue is regulated by the use of two promoters which differ from the prevalent placental one. The adipose transcripts contain a distinct untranslated first exon, 0a or 0b, followed by a common partially translated exon 1b, and nine other exons that are also shared by the main placental transcript. The presence of an upstream open reading frame in the new transcript variants could lead to an N-terminal divergence restricted to the cleavable signal peptide and thus not interfering with the catalytic activity of the mature STS protein. The adipose transcripts are also present in the placenta as minor isoforms. Western blotting revealed the characteristic approximately 64 kDa band of STS in both the placenta and adipose tissue. The specific enzymatic activity of STS in adipocytes was 118 pmol/10(6) cells per hour, about 50-100 times lower than in the placenta. A similar rate of [3H] DHEA-S uptake plus desulfation was measured in preadipocytes and adipocytes, equivalent to 40-45 pmol/10(6) cells per hour. Thus, an excessive accumulation of fat may out-compete other peripheral organs that are also dependent on intracrine DHEA-S utilization, especially when the adrenal production is low or declining with aging.
...
PMID:Tissue-specific transcriptional initiation and activity of steroid sulfatase complementing dehydroepiandrosterone sulfate uptake and intracrine steroid activations in human adipose tissue. 1683 17

trans-Resveratrol is a polyphenol present in several plant species. Its chemopreventive properties against several diseases have been largely documented. To validate a model for the study of the factors influencing its biological fate at the hepatic level, the metabolism and the efflux of resveratrol were studied in the human hepatoblastoma cell line, HepG2. Comparative high-performance liquid chromatography analysis of cell culture media before and after deconjugation showed that resveratrol was rapidly conjugated; at the concentration of 10 microM, it was entirely metabolized at 8 h of incubation. Two main resveratrol metabolites, monosulfate and disulfate, were identified by atmospheric pressure chemical ionization-mass spectrometry, thanks to their quasi-molecular ion and their characteristic fragmentation. To correlate with the auto-induction of resveratrol metabolism evidenced in HepG2 cells after a pretreatment for 48 h with 10 microM resveratrol, the inducibility of phase II enzymes by resveratrol was studied by real-time quantitative reverse transcriptase-polymerase chain reaction and flow cytometry. Observed, in particular, were an increase in mRNA expression levels of three metabolizing enzymes, two isoforms of UDP-glucuronosyltransferases, UGT1A1 and UGT2B7 (5-fold increased), and a sulfotransferase, ST1E1, in cells pretreated for 24 h with 10 microM resveratrol. These results were correlated with an increase in protein expression, especially after 48 h of treatment. On the other hand, the intracellular resveratrol retention in cells treated with MK571 (3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid), a multidrug resistance-associated protein inhibitor, strongly suggests the involvement of this ABC transporter family in the efflux of resveratrol conjugates from human liver.
...
PMID:Resveratrol in human hepatoma HepG2 cells: metabolism and inducibility of detoxifying enzymes. 1728 90


1 2 Next >>

---