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)

We characterized catabolite repression of the genes encoding xylose utilization in Bacillus megaterium. A transcriptional fusion of xylA encoding xylose isomerase to the spoVG-lacZ indicator gene on a plasmid with a temperature-sensitive origin of replication was constructed and efficiently used for single-copy replacement cloning in the B. megaterium chromosome starting from a single transformant. In the resulting strain, beta-galactosidase expression is 150-fold inducible by xylose and 14-fold repressed by glucose, showing that both regulatory effects occur at the level of transcription. Insertion of a kanamycin resistance gene into xylR encoding the xylose-dependent repressor leads to the loss of xylose-dependent regulation and to a small drop in the efficiency of glucose repression to eightfold. Deletion of 184 bp from the 5' part of the xylA reading frame reduces glucose repression to only twofold. A potential glucose-responsive element in this region is discussed on the basis of sequence similarities to other glucose-repressed genes in Bacillus subtilis. The sequence including the glucose-responsive element is also necessary for repression exerted by the carbon sources fructose and mannitol. Their efficiencies of repression correlate to the growth rate of B. megaterium, as is typical for catabolite repression. Glycerol, ribose, and arabinose exert only a basal twofold repression of the xyl operon, which is independent of the presence of the cis-active glucose-responsive element within the xylA reading frame.
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PMID:Catabolite repression of the xyl operon in Bacillus megaterium. 156 31

A number of bacterial isolates which could not be identified as either Salmonella or Citrobacter by conventional biochemical tests and could not be typed as Salmonella with available antisera, were further examined biochemically and by lysis with phage Felix 0.1. Glycerol-positive salmonellae and lysine-positive citrobacters were encountered, which could be confused with the other genus, but when the reactions of such strains were examined in the other tests, accurate identifications could be done. Of the tests examined, glycerol fermentation, the beta-galactosidase test, lysine decarboxylation, sorbose fermentation, galacturonate fermentation and lysis by the phage could be used in the differentiation. These tests in combination, rather than 1 or 2 single tests gave reliable and conclusive differentiation.
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PMID:The biochemical differentiation between Salmonella and Citrobacter. 269 17

When cells of Escherichia coli ML30 were suspended in 2% gelatin and frozen at -40 C, no appreciable metabolic damage or death occurred. After freeze-drying for 8 hr at a platen temperature of 49 C and rehydration with a mineral salts medium, survival of the cells was 0.6%. Metabolic damage of the survivors was found to be 23%. Permeability alterations were detected by several criteria. Freeze-dried cells were susceptible to antibiotics normally ineffective against E. coli and leakage of ribonucleic acid (RNA) occurred. Analysis of ribosomal extracts of rehydrated freeze-dried cells demonstrated the presence of appreciable degradation products. Permeability alterations were shown to be reversible by the observation that antibiotic susceptibility was a time-dependent process and that the gratuitous inducer of beta-galactosidase was not concentrated by freeze-dried cells until the injured cells had been incubated in a nutrient medium for 300 min or more. At approximately the same time, metabolic damage was repaired. RNA synthesis preceded protein synthesis by about 150 min, and deoxyribonucleic acid synthesis occurred with the resumption of normal growth. This was interpreted to be the result of repair of RNA taking place before protein synthesis and growth could resume. A pronounced increase in the lag time of freeze-dried cells was also observed. Peptides and Casamino Acids shortened the lag time for freeze-dried cells but not for the controls. Glycerol and glucose were found to be better carbon sources for growth of freeze-dried cells than sodium lactate or sodium succinate.
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PMID:Characterization of injury incurred by Escherichia coli upon freeze-drying. 490 8

In order to relate the biogenesis of the lactose transport system to lipid synthesis, a glycerol-requiring mutant of Escherichia coli K-12 with a specific defect in l-glycerol-3-phosphate synthesis was isolated and characterized. The defective enzyme is the biosynthetic l-glycerol-3-phosphate dehydrogenase [l-glycerol-3-phosphate: NAD (P) oxidoreductase, EC 1.1.1.8] which functions as a dihydroxyacetone phosphate reductase to provide l-glycerol-3-phosphate for lipid synthesis. In this mutant, removal of glycerol from the growth medium results in inhibition of the synthesis of protein, deoxyribonucleic acid, and phospholipid. Inhibition of phospholipid synthesis immediately follows glycerol removal, whereas the inhibition of deoxyribonucleic acid and protein synthesis is preceded by a short lag period. Glycerol starvation does not change the turnover pattern of previously synthesized phospholipids. The blocking of lipid synthesis by glycerol starvation causes a drastic decrease in inducibility of beta-galactoside transport activity relative to beta-galactosidase, indicating that induction of lactose transport requires de novo lipid synthesis.
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PMID:Induction of the lactose transport system in a lipid-synthesis-defective mutant of Escherichia coli. 491 67

In order to study transcriptional regulation of hepatic genes during development, a method for transfer of fusion genes to primary cultures of fetal hepatocytes was required. The aim of this study was to assess currently available transfection methods and optimize the best method for use with cultured fetal hepatocytes. The Rous sarcoma virus 5' long terminal repeat controlling transcription of the beta-galactosidase reporter gene (pRSV lac Z II) was used to assess electroporation, lipofection, DEAE-dextran and calcium phosphate transfection in cultured primary fetal hepatocytes. The success of transfection was determined by histochemical detection and quantitation of beta-galactosidase activity. Results showed that calcium phosphate transfection was optimal for fetal hepatocytes with respect to beta-galactosidase activity and cell survival. For maximum transfection of cells, 10 micrograms/ml DNA, HEPES buffered saline transfection buffer at pH 7.05 and a 24 hr expression period for the reporter gene were employed. Glycerol shock did not increase transfection efficiency significantly. The method was simplified by adding calcium chloride solution to DNA diluted in transfection buffer and the resulting co-precipitate added directly to the medium covering the cells. Transfection 24 hr after initial culture and a precipitate incubation time of 20 hr were optimal. The suitability of this method was confirmed with a liver-specific promoter controlling beta-galactosidase and chloramphenicol acetyltransferase expression. In conclusion this study shows that a modified calcium phosphate transfection method is most effective for transferring DNA to primary cultured fetal hepatocytes. It is concluded that this method is appropriate for use with fetal hepatocytes and will facilitate studies of gene regulation during liver development.
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PMID:Calcium phosphate transfection and cell-specific expression of heterologous genes in primary fetal rat hepatocytes. 867 28

The glycerol phosphate shuttle consists of FAD-linked mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) and its cytosolic NAD-linked isoform (cGPDH). Impaired mGPDH activity has recently been suggested to be one of the primary causes of insulin secretory defects in beta-cells. We found that mGPDH and cGPDH activities in MIN6 cells are comparable to those of isolated islets and higher than those in HIT cells by eightfold and threefold, respectively. Therefore, we selected the MIN6 cell line as a beta-cell model with normally regulated insulin secretion and normal shuttle enzyme activities and the HIT cell line as a beta-cell model with impaired insulin secretion and lower activities of these enzymes. The role of these dehydrogenases in glucose-stimulated insulin secretion was addressed by examining the effects of overexpression of mGPDH and/or cGPDH via recombinant adenoviruses in these cells. Infection with recombinant adenovirus with a cDNA encoding the Escherichia coli beta-galactosidase gene resulted in expression of its gene in 90% of MIN6 and HIT cells. Infection with a recombinant adenovirus with mGPDH cDNA (Adex1CAmGPDH) caused 2.1-fold and 5.7-fold increases in dehydrogenase activity as compared with those of control MIN6 and HIT cells, respectively. Infection with a recombinant adenovirus with cGPDH cDNA (Adex1CAcGPDH) caused a more than 50-fold increase in activity in both cell lines. Glycerol phosphate shuttle flux, as estimated by [2-3H]glycerol conversion to [3H]H2O, was increased to 120-130% by infection with Adex1CAmGPDH, but not with Adex1CAcGPDH infection, in both MIN6 and HIT cells. No further increase in flux through the glycerol phosphate shuttle was detected when the cells were infected with Adex1CAmGPDH together with Adex1CAcGPDH. Furthermore, neither [U-14C]glucose oxidation nor the insulin secretory response to glucose was affected in either cell line. Thus, mGPDH abundance in MIN6 and HIT cells is not directly related to their insulin secretory capacity in response to glucose, and reduced expression of mGPDH is not the primary cause of abnormal insulin secretory responses in HIT cells. The present data indicate that the emerging hypothesis pointing to mGPDH deficiency as a possible cause of NIDDM needs to be carefully evaluated.
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PMID:Effect of mitochondrial and/or cytosolic glycerol 3-phosphate dehydrogenase overexpression on glucose-stimulated insulin secretion from MIN6 and HIT cells. 877 29

gamma-Glutamyl transpeptidase (GGT, EC 2.3.2.2.) catalyzes the transfer of the gamma-glutamyl moiety from gamma-glutamylcontaining compounds, notably glutathione (GSH), to acceptor amino acids and peptides. A second gene (GGTII) encoding GGT was previously isolated and characterized from the fission yeast Schizosaccharomyces pombe. In the present work, the GGTII-lacZ fusion gene was constructed and used to study the transcriptional regulation of the S. pombe GGTII gene. The synthesis of beta-galactosidase from the GGTII-lacZ fusion gene was significantly enhanced by NO-generating SNP and hydrogen peroxide in the wildtype yeast cells. The GGTII mRNA level was increased in the wild-type S. pombe cells treated with SNP. However, the induction by SNP was abolished in the Pap1-negative S. pombe cells, implying that the induction by SNP of GGTII is mediated by Pap1. Fermentable carbon sources, such as glucose (at low concentrations), lactose and sucrose, as a sole carbon source, enhanced the synthesis of beta-galactosidase from the GGTII-lacZ fusion gene in wildtype KP1 cells but not in Pap1-negative cells. Glycerol, a non-fermentable carbon source, was also able to induce the synthesis of beta-galactosidase from the fusion gene, but other non-fermentable carbon sources such as acetate and ethanol were not. Transcriptional induction of the GGTII gene by fermentable carbon sources was also confirmed by increased GGTII mRNA levels in the yeast cells grown with them. Nitrogen starvation was also able to induce the synthesis of beta-galactosidase from the GGTII-lacZ fusiongene in a Pap1-dependent manner. On the basis of the results, it is concluded that the S. pombe GGTII gene is regulated by oxidative and metabolic stress.
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PMID:The gene encoding gamma-glutamyl transpeptidase II in the fission yeast is regulated by oxidative and metabolic stress. 1620 43

Glycerol auxotrophs of S. aureus were isolated and shown to cease phospholipid synthesis immediately when deprived of glycerol. Second-step mutants with temperature-sensitive inducibility of the lac system were also isolated. When cells were induced by temperature shift to produce the products of the lac system in the absence of glycerol, the permease activity, relative to 6-phospho-beta-galactosidase activity, was between 30 and 50% that of glycerol-supplemented cultures. However, the phosphotransferase activity for beta-galactosides in isolated membranes was found to be normal when compared to the level of beta-galactosidase. This indicated that the permeation system was induced and integrated into the membrane, but did not function efficiently for transport. Readdition of glycerol in the presence of chloramphenicol resulted in a slow increase in efficiency of the transport activity. Glycerol deprivation after induction led to a small loss of permease efficiency.
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PMID:Induction of Staphylococcus aureus Lactose Permease in the Absence of Glycerolipid Synthesis. 1659 7