Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adrenodoxin reductase (AR; ferridoxin: NADP+ oxidoreductase, EC 1.18.1.2) is a flavoprotein that mediates electron transport from NADPH to all known mitochondrial forms of cytochrome P450. AR mRNA was found in all human adult and fetal tissues examined; however, it was vastly more abundant in tissues that synthesize steroid hormones. The ratio of the 18- form of mRNA lacking 18 alternately spliced bases to the 18+ form was approximately 100:1 and remained constant irrespective of the tissue or hormonal manipulation, indicating that the alternate splicing is a passive nonregulated event. AR protein was unchanged by forskolin treatment of human JEG-3 cytotrophoblast cells for 24 h, but the mRNA diminished. Phorbol 12-myristate 13-acetate and cycloheximide had no effect, even though these agents had the expected effects on P450scc and adrenodoxin mRNAs. cAMP decreased the abundance of AR mRNA expressed from both transfected plasmids and the endogenous gene, indicating the effect was post-transcriptional. AR gene transcription in JEG-3 cells and promoter-chloramphenicol acetyltransferase constructs transfected into JEG-3 cells were unresponsive to forskolin. Powerful basal transcription elements were identified between -46 and -214 bases from the principal transcriptional initiation site, a region containing six elements closely resembling the binding site for transcription factor SP1.
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PMID:cAMP post-transcriptionally diminishes the abundance of adrenodoxin reductase mRNA. 131 50

The human 11 beta-hydroxysteroid dehydrogenase (h11 beta-HSD) inactivates the active corticosteroid cortisol to its inactive metabolite cortisone. We have developed transactivation analyses of the reporter chimeric gene mouse mammary tumor virus-chloramphenicol acetyltransferase (MMTV-CAT) to study the catalytic activity of h11 beta-HSD introduced by cotransfection into receptor and 11 beta-HSD deficient CV-1 cells. Assay of 11 beta-HSD expressed in CV-1 cells by cotransfection showed that the catalyzed dehydrogenation of cortisol to cortisone was 2-fold higher in the presence of NADP. The reductase activity was dependent on the coenzyme NADPH. The addition of increasing concentrations of the inhibitor carbenoxolone (CBX) in the incubates blocked the enzyme activity in a dose dependent fashion. In CV-1 cells cotransfected with expression vectors of either human glucocorticoid (hGR1-777) or mineralocorticoid (hMR1-984) and the reporter plasmid MMTV-CAT, dexamethasone (DEX), aldosterone (ALDO), cortisol, and corticosterone induction of CAT activity was dose dependent. Cotransfection of CV-1 cells transfected with 10 micrograms of 11 beta-HSD expression vector reduced the transactivation of MMTV-CAT by hGR or hMR in the presence of either cortisol or corticosterone to basal values. The concomitant addition of 100 nM cortisone and 1 microM NADPH to these transfectants elevated CAT activity. These data show that transactivation analyses can be used to study the 11 beta-HSD-catalyzed regulation of corticosteroid levels, which triggers physiological processes and in certain cases provides an alternative to animal experimentation.
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PMID:Transcription activation of mouse mammary tumor virus-chloramphenicol acetyltransferase: a model to study the metabolism of cortisol. 794 89

We have identified a cell surface ferric reductase activity in the fission yeast Schizosaccharomyces pombe. A mutant strain deficient in this activity was also deficient in ferric iron uptake, while ferrous iron uptake was not impaired. Therefore, reduction is a required step in cellular ferric iron acquisition. We have cloned frp1+, the wild-type allele of the mutant gene. frp1+ mRNA levels were repressed by iron addition to the growth medium. Fusion of 138 nucleotides of frp1+ promoter sequences to a reporter gene, the bacterial chloramphenicol acetyltransferase gene, conferred iron-dependent regulation upon the latter when introduced into S. pombe. The predicted amino acid sequence of the frp1+ gene exhibits hydrophobic regions compatible with transmembrane domains. It shows similarity to the Saccharomyces cerevisiae FRE1 gene product and the gp91-phox protein, a component of the human NADPH phagocyte oxidoreductase that is deficient in X-linked chronic granulomatous disease.
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PMID:The fission yeast ferric reductase gene frp1+ is required for ferric iron uptake and encodes a protein that is homologous to the gp91-phox subunit of the human NADPH phagocyte oxidoreductase. 832 Dec 36

Aldose reductase (EC 1.1.1.21) catalyzes the NADPH-mediated conversion of glucose to sorbitol. The hyperglycemia of diabetes increases sorbitol production primarily through substrate availability and is thought to contribute to the pathogenesis of many diabetic complications. Increased sorbitol production can also occur at normoglycemic levels via rapid increases in aldose reductase transcription and expression, which have been shown to occur upon exposure of many cell types to hyperosmotic conditions. The induction of aldose reductase transcription and the accumulation of sorbitol, an organic osmolyte, have been shown to be part of the physiological osmoregulatory mechanism whereby renal tubular cells adjust to the intraluminal hyperosmolality during urinary concentration. Previously, to explore the mechanism regulating aldose reductase levels, we partially characterized the human aldose reductase gene promoter present in a 4.2-kb fragment upstream of the transcription initiation start site. A fragment (-192 to +31 bp) was shown to contain several elements that control the basal expression of the enzyme. In this study, we examined the entire 4.2-kb human AR gene promoter fragment by deletion mutagenesis and transfection studies for the presence of osmotic response enhancer elements. An 11-bp nucleotide sequence (TGGAAAATTAC) was located 3.7 kb upstream of the transcription initiation site that mediates hypertonicity-responsive enhancer activity. This osmotic response element (ORE) increased the expression of the chloramphenicol acetyltransferase reporter gene product 2-fold in transfected HepG2 cells exposed to hypertonic NaCl media as compared with isoosmotic media. A more distal homologous sequence is also described; however, this sequence has no osmotic enhancer activity in transfected cells. Specific ORE mutant constructs, gel shift, and DNA fragment competition studies confirm the nature of the element and identify specific nucleotides essential for enhancer activity. A plasmid construct containing three repeat OREs and a heterologous promoter increased expression 8-fold in isoosmotic media and an additional 4-fold when the transfected cells are subjected to hyperosmotic stress (total approximately 30-fold). These findings will permit future studies to identify the transcription factors involved in the normal regulatory response mechanism to hypertonicity and to identify whether and how this response is altered in a variety of pathologic states, including diabetes.
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PMID:Characterization of the osmotic response element of the human aldose reductase gene promoter. 871 Sep 21

Aldose reductase (AR; EC 1.1.1.21) is an oxidoreductase that catalyzes the NADPH-dependent conversion of glucose to sorbitol, the first step of the polyol pathway. AR is of great interest due to its implication in the etiology of diabetic complications. In renal medullary cells, AR also plays an osmoregulatory role by accumulating sorbitol to maintain the intracellular osmotic balance during antidiuresis. We have previously cloned the AR cDNA from mouse kidney, and we report here the isolation of the mouse AR gene promoter. Transient transfection of chloramphenicol acetyltransferase reporter constructs containing various 5'-flanking regions of the mouse AR gene in CV1 cells led to the identification of a sequence spanning base pairs -1053 to -1040, required for an enhancer activity in hypertonic compared with isotonic cell culture conditions. This sequence is similar to the tonicity-responsive element first characterized in the betaine-gamma-aminobutyric acid transporter promoter.
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PMID:Isolation of the mouse aldose reductase promoter and identification of a tonicity-responsive element. 900 94

Glyoxylate is an important intermediate of the central microbial metabolism formed from acetate, allantoin or glycolate. Depending on the physiological conditions, glyoxylate is incorporated into the central metabolism by the combined actions of the activity of malate synthase and the D-glycerate pathway, or alternatively it can be reduced to glycolate by constitutive glyoxylate reductase activity. At present no information is available on this latter enzyme in Escherichia coli, although similar enzymes, classified as 2-hydroxyacid dehydrogenases, have been characterized in other organisms. A BLAST search using as the query sequence the hydroxypyruvate/glyoxylate reductase from Cucumis sativus identified as an orthologue the yiaE gene of E. coli encoding a ketoaldonate reductase. Use of this sequence in a subsequent BLAST search yielded the ycdW gene as a good candidate to encode glyoxylate reductase in this bacterium. Cloning and overexpression of the ycdW gene showed that its product displayed a high NADPH-linked glyoxylate reductase activity, and also catalysed the reduction of hydroxypyruvate with a lower efficiency. Disruption of the ycdW gene by a chloramphenicol acetyltransferase ('CAT') cassette did not totally abolish the glyoxylate reductase activity, indicating that another enzyme accomplished this function. The similarity with YiaE led us to test whether this protein was responsible for the remaining glyoxylate reductase activity. Purification of YcdW and YiaE proteins permitted their kinetic characterization and comparison. Analysis of the catalytic power (k(cat)/K(m)) disclosed a higher ratio of YcdW for glyoxylate and of YiaE for hydroxypyruvate.
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PMID:Biochemical characterization of the 2-ketoacid reductases encoded by ycdW and yiaE genes in Escherichia coli. 1123 76

Transaldolase regulates redox-dependent apoptosis through controlling NADPH and ribose 5-phosphate production via the pentose phosphate pathway. The minimal promoter sufficient to drive chloramphenicol acetyltransferase reporter gene activity was mapped to nucleotides -49 to -1 relative to the transcription start site of the human transaldolase gene. DNase I footprinting with nuclear extracts of transaldolase-expressing cell lines unveiled protection of nucleotides -29 to -16. Electrophoretic mobility shift assays identified a single dominant DNA-protein complex that was abolished by consensus sequence for transcription factor ZNF143/76 or mutation of the ZNF76/143 motif within the transaldolase promoter. Mutation of an AP-2alpha recognition sequence, partially overlapping the ZNF143 motif, increased TAL-H promoter activity in HeLa cells, without significant impact on HepG2 cells, which do not express AP-2alpha. Cooperativity of ZNF143 with AP-2alpha was supported by supershift analysis of HeLa cells where AP-2 may act as cell type-specific repressor of TAL promoter activity. However, overexpression of full-length ZNF143, ZNF76, or dominant-negative DNA-binding domain of ZNF143 enhanced, maintained, or abolished transaldolase promoter activity, respectively, in HepG2 and HeLa cells, suggesting that ZNF143 initiates transcription from the transaldolase core promoter. ZNF143 overexpression also increased transaldolase enzyme activity. ZNF143 and transaldolase expression correlated in 21 different human tissues and were coordinately upregulated 14- and 34-fold, respectively, in lactating mammary glands compared with nonlactating ones. Chromatin immunoprecipitation studies confirm that ZNF143/73 associates with the transaldolase promoter in vivo. Thus, ZNF143 plays a key role in basal and tissue-specific expression of transaldolase and regulation of the metabolic network controlling cell survival and differentiation.
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PMID:ZNF143 mediates basal and tissue-specific expression of human transaldolase. 1470 49