Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Enzyme Repression”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
PubMed1982

Regulation of the phosphatidylethanolamine methylation pathway in Saccharomyces cerevisiae.

1. Phosphatidyl-N-methylethanolamine methyltransferase mutants of Saccharomyces cerevisiae were isolated. Genetic analysis showed that phosphatidylethanolamine methyltransferase and phosphatidyl-N-methylethanolamine methyltransferase are coded for by separate genes. Phosphatidyl-N-methylethanolamine methyltransferase activity and phosphatidyl-N,N-dimethylethanolamine methyltransferase activity appeared to be catalyzed by the same enzyme. 2. Phosphatidyl-N-methylethanolamine methyltransferase was found to be repressed by myo-inositol and choline. Both myo-inositol and choline at concentrations of 10 micrograms/ml were required for repression. The decreased enzyme level was restored by the removal of myo-inositol or choline or both. 3. Both myo-inositol and choline were required for the maximum repression of phosphatidylethanolamine methyltransferase in wild-type cells. In contrast, choline was not required for the repression of the enzyme in mutant strain 172. This was due to a single nuclear gene mutation in the genome of strain 172. 4. The activity of the phosphatidylethanolamine methylation pathway in cells decreased with time on incubation of cells with myo-inositol and choline, myo-Inositol could not be replaced by other structurally related compounds, such as scyllo-inositol or mannitol. 5. The physiological significance of the repression of the phosphatidylethanolamine methylation pathway is discussed with respect to the mechanism for maintaining the contents of phosphatidylethanolamine and phosphatidylcholine at normal levels.

Choline↗
PubMed1977

An evaluation of D-glucosamine as a gratuitous catabolite repressor of Saccharomyces carlsbergensis.

Glucose represses mitochondrial biogenesis and the fermentation of maltose, galactose and sucrose in yeast. We have analyzed the effect of D-glucosamine on these functions in order to determine if it can produce a similar repression. It was found that glucosamine represses the respiration rate (QO2) but more rapidly than glucose and to a final level slightly higher than in glucose-treated cells. Derepression of the respiration rate following either glucose or glucosamine repression was similar. A two hour lag was followed by a linear increase in QO2 to the derepressed level. Both glucose and glucosamine repressed the level of cytochrome oxidase to the same level. Glucosamine was also found to repress maltose and galactose fermentation but not sucrose fermentation. The derepression of maltase synthesis was inhibited by glucosamine. The constitutive synthesis of maltase was repressed by the addition of glucosamine. Glucosamine was judged to produce a repressed state similar to glucose repression in many respects.

Electron Transport Complex IV↗
PubMed1992

Glucose repression in the yeast Saccharomyces cerevisiae.

Understanding the mechanism of glucose repression in yeast has proved to be a difficult and challenging problem. A multitude of genes in different pathways are repressed by glucose at the level of transcription. The SUC2 gene, which encodes invertase, is an excellent reporter gene for glucose repression, since its expression is controlled exclusively by this pathway. Genetic analysis has identified numerous regulatory mutations which can either prevent derepression of SUC2 or render its expression insensitive to glucose repression. These mutations allow us to sketch the outlines of a pathway for general glucose repression, which has several key elements: hexokinase PII, encoded by HXK2, which seems to play a role in the sensing of glucose levels; the protein kinase encoded by SNF1, whose activity is required for derepression of many glucose-repressible genes; and the MIG1 repressor protein, which binds to the upstream regions of SUC2 and other glucose-repressible genes. Repression by MIG1 requires the activity of the CYC8 and TUP1 proteins. Glucose repression of other sets of genes seems to be controlled by the general glucose repression pathway acting in concert with other mechanisms. In the cases of the GAL genes and possibly CYC1, regulation is mediated by a cascade in which the general pathway represses expression of a positive transcriptional activator.

Cytochrome c Group↗
PubMed1967

Pyrimidine nucleotide synthesis: regulatory control during transformation of lymphocytes in vitro.

The incorporation of uridine into RNA in lymphocytes undergoing transformation induced by phytohemagglutinin parallels its incorporation into the intratcellular pool of acid-soluble nucleotides and coincides with a 20-fold increase in the specific activity of uridine kinase. This increase is dependent upon synthesis of both RNA and protein and is subject to both repression and end-product inhibition by cytidine.

Cell Differentiation↗
PubMed1983

Cyclic AMP may not be involved in catabolite repression in Saccharomyces cerevisiae: evidence from mutants unable to synthesize it.

Yeast cells with a nonsense adenylate cyclase mutation, cyr1-3, required cyclic AMP for growth. This phenotype was suppressed by the byc1 mutation; however, cyr1-3 bcy1 cells produced no detectable level of adenylate cyclase or cyclic AMP. On induction, the bcy1 and cyr1-3 bcy1 mutant cells produced the same levels of galactokinase and alpha-D-glucosidase as did the wild-type cells and fourfold-higher levels of invertase. Since galactokinase synthesis was severely repressed by glucose in the constitutive GAL81 mutants, irrespective of the cyr1-3 bcy1 genotype, cyclic AMP may not be involved in catabolite repression.

Adenylyl Cyclases↗
PubMed1966

Regulation of synthesis of alkaline phosphatase by deoxyribonucleic acid synthesis in a constitutive mutant of Bacillus subtilis.

Hiraga, Sota (Osaka University, Osaka, Japan). Regulation of synthesis of alkaline phosphatase by deoxyribonucleic acid synthesis in a constitutive mutant of Bacillus subtilis. J. Bacteriol. 91:2192-2199. 1966.-It was found that synthesis of alkaline phosphatase (APase) correlated with deoxyribonucleic acid (DNA) synthesis in a partially constitutive mutant of Bacillus subtilis. When cultures of the mutant were made to undergo synchronous growth by germination of spores in an excess-phosphate medium, synthesis of APase was repressed at the beginning of DNA synthesis. If the initiation of DNA synthesis was inhibited by thymine starvation, the repression of APase was not observed. When DNA synthesis, previously initiated, was inhibited by thymine or uracil starvation, or by addition of mitomycin C, the repression was partially released at a later stage. In contrast, this correlation between repression and DNA synthesis was not observed in a repressible strain.

Alkaline Phosphatase↗
PubMed2005

Hierarchical control of anaerobic gene expression in Escherichia coli K-12: the nitrate-responsive NarX-NarL regulatory system represses synthesis of the fumarate-responsive DcuS-DcuR regulatory system.

Hierarchical control ensures that facultative bacteria preferentially use the available respiratory electron acceptor with the most positive standard redox potential. Thus, nitrate is used before other electron acceptors such as fumarate for anaerobic respiration. Nitrate regulation is mediated by the NarX-NarL two-component system, which activates the transcription of operons encoding nitrate respiration enzymes and represses the transcription of operons for other anaerobic respiratory enzymes, including enzymes involved in fumarate respiration. These are fumarate reductase (encoded by the frdABCD operon), fumarase B, which generates fumarate from malate, and the DcuB permease for fumarate, malate, and aspartate. The transcription of the corresponding structural genes is activated by the DcuS-DcuR two-component system in response to fumarate or its dicarboxylate precursors. We report results from preliminary transcription microarray experiments that revealed two previously unknown members of the NarL regulon: the aspA gene encoding aspartate-ammonia lyase, which generates fumarate; and the dcuSR operon encoding the dicarboxylate-responsive regulatory system. We measured beta-galactosidase expression from monocopy aspA-lacZ, frdA-lacZ, and dcuS-lacZ operon fusions in response to added nitrate and fumarate and with respect to the dcuR and narL genotypes. Nitrate, acting through the NarX-NarL regulatory system, repressed the transcription of all three operons. Only frdA-lacZ expression, however, was responsive to added fumarate or a dcuR(+) genotype. Phospho-NarL protein protected operator sites in the aspA and dcuS promoter regions from DNase I cleavage in vitro. The overall results are consistent with the hypothesis that nitrate represses frdA operon transcription not only directly, by repressing frdA promoter activity, but also indirectly, by repressing dcuS promoter activity.

Amino Acid Sequence↗