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)

Addition of 0.5% (w/v) lactose to a glucose-mineral mdeium (SM) induced formation of sclerotia and beta-D-galactosidase (beta-D-galactoside galactohydrolase)(EC 3.2.1.23) synthesis in Sclerotium rolfsii types A and R; These effects as well as lactose uptake were inversely related to glucose concentration within the tested range of 0.5 to 2.5% (w/v). Transfer of lactose-grown colonies to a glucose-supplemented medium nullified the inducible effect of lactose on formation of sclerotia, whereas transfer to water agar did not. It is concluded that glucose nullifies the effect of lactose on S. rolfsii by interfering with its active uptake.
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PMID:The effect of glucose and lactose on beta-D-galactosidase activity and formation of sclerotia in Sclerotium rolfsii. 117 Sep 31

Studies have been carried out on activities of lysosomal beta-N-acetylhexosaminidase (hex), beta-galactosidase (beta-gal), alpha-glucosidase (alpha-glu), and acid phosphatase (AP) in serum and urine from patients with juvenile diabetes and matched controls. There is a large increase in blood and urinary hex activity (the former presenting three distinct patterns of abnormality), a moderate increase in urinary beta-gal, and a small increase in urinary alpha-glu activity, but no elevation of blood or urinary AP in the diabetics. Urinary alpha-glu activity in the diabetics shows striking inhibition by glucose, and this may reflect a similar phenomenon in vivo. Although glycohydrolase activities are elevated in patients with no detectable microangiopathy, more striking changes may be observed in patients with severe small-vessel disease. These alterations may be associated with increased glycoprotein catabolism in the diabetic, an area in need of further studies in the human and experimental diabetic animal.
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PMID:Altered lysosomal glycohydrolase activities in juvenile diabetes mellitus. 126 40

The LPD1 gene of Saccharomyces cerevisiae, encoding lipoamide dehydrogenase (LPDH), is subject to catabolite repression. The promoter of this gene contains a number of motifs for DNA-binding transcriptional activators, including three which show strong sequence homology to the core HAP2/HAP3/HAP4 binding motif. Here we report that transcription of LPD1 requires HAP2, HAP3 and HAP4 for release from glucose repression. In the wild-type strain, specific activity of LPDH was increased 12-fold by growth on lactate, 10-fold on glycerol and four- to five-fold on galactose or raffinose, compared to growth on glucose. In hap2, hap3 and hap4 null mutants, the specific activities of LPDH in cultures grown on galactose and raffinose showed only slight induction above the basal level on glucose medium. Similar results were obtained upon assaying for beta-galactosidase production in wild-type, or hap2, hap3 or hap4 mutant strains carrying a single copy of the LPD1 promoter fused in frame to the lacZ gene of Escherichia coli and integrated at the URA3 locus. Transcript analysis in wild-type and hap2 mutants confirmed that the HAP2 protein regulates LPD1 expression at the level of transcription in the same way as it does for the CYC1 gene. Site-directed mutagenesis of the putative HAP2/HAP3/HAP4 binding site at -204 relative to the ATG start codon showed that this element was required for full derepression of the LPD1 gene on non-fermentable substrates.
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PMID:Positive regulation of the LPD1 gene of Saccharomyces cerevisiae by the HAP2/HAP3/HAP4 activation system. 131 May 23

Expression of the Vibrio fischeri luminescence genes (luxR and luxICDABEG) in Escherichia coli requires autoinducer (N-3-oxohexanoyl homoserine lactone) and LuxR protein, which activate transcription of luxICDABEG (genes for autoinducer synthase and the luminescence enzymes), and cyclic AMP (cAMP) and cAMP receptor protein (CRP), which activate transcription of the divergently expressed luxR gene. In E. coli and in V. fischeri, the autoinducer-LuxR protein-dependent induction of luxICDABEG transcription (called autoinduction) is delayed by glucose, whereas it is promoted by iron restriction, but the mechanisms for these effects are not clear. To examine in V. fischeri control of lux gene expression by autoinducer, cAMP, glucose, and iron, lux::Mu dI(lacZ) and lux deletion mutants of V. fischeri were constructed by conjugation and gene replacement procedures. beta-Galactosidase synthesis in a luxC::lacZ mutant exhibited autoinduction. In a luxR::lacZ mutant, complementation by the luxR gene was necessary for luminescence, and addition of cAMP increased beta-galactosidase activity four- to sixfold. Furthermore, a luxI::lacZ mutant produced no detectable autoinducer but responded to its addition with induced synthesis of beta-galactosidase. These results confirm in V. fischeri key features of lux gene regulation derived from studies with E. coli. However, beta-galactosidase specific activity in the luxI::lacZ mutant, without added autoinducer, exhibited an eight- to tenfold decrease and rise back during growth, as did beta-galactosidase and luciferase specific activities in the luxR::lacZ mutant and luciferase specific activity in a delta(luxR luxICD) mutant. The presence of glucose delayed the rise back in beta-galactosidase and luciferase specific activities in these strains, whereas iron restriction promoted it. Thus, in addition to transcriptional control by autoinducer and LuxR protein, the V. fischeri lux system exhibits a cell density-dependent modulation of expression that does not require autoinducer, LuxR protein, or known lux regulatory sites. The response of autoinducer-LuxR protein-independent modulation to glucose and iron may account for how these environmental factors control lux gene expressions.
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PMID:Cell density-dependent modulation of the Vibrio fischeri luminescence system in the absence of autoinducer and LuxR protein. 131 12

Northern-blot analysis was used to demonstrate that an increase in extracellular glucose concentration increased the content of preproinsulin mRNA 2.3-fold in the beta-cell line HIT T15. A probe for the constitutively expressed glyceraldehyde-3-phosphate dehydrogenase was used as a control. Mannoheptulose blocked this effect of glucose. A stimulatory effect on preproinsulin mRNA levels was also observed in response to mannose and to 4-methyl-2-oxopentanoate. However, galactose and arginine were ineffective. Glucagon, forskolin and dibutyryl cyclic AMP also elicited an increase in HIT-cell preproinsulin mRNA. The ability of the 5' upstream region of the preproinsulin gene to mediate the effect of glucose and other metabolites on transcription was studied by using a bacterial reporter gene technique. HIT cells were transfected with a plasmid, pOK1, containing the upstream region of the rat insulin-1 gene (-345 to +1) linked to chloramphenicol acetyltransferase (CAT). Co-transfection with a plasmid pRSV beta-gal containing beta-galactosidase driven by the Rous sarcoma virus promoter was used as a control for the efficiency of transfection; expression of CAT activity in transfected HIT cells was normalized by reference to expression of beta-galactosidase. Glucose caused a dose-dependent increase in expression of CAT activity, with a half-maximal effect at 5.5 mM and a maximum response of 4-fold. Mannoheptulose blocked this effect of glucose. Other metabolites (mannose, 4-methyl-2-oxopentanoate and leucine plus glutamine) were also able to increase insulin promoter-driven CAT expression, but galactose and arginine were ineffective. The stimulatory effect of glucose on CAT expression was not blocked by verapamil and was inhibited by increasing extracellular Ca2+ from 0.4 to 5 mM. Both dibutyryl cyclic AMP and forskolin caused an increase in insulin promoter-driven gene expression in the presence of 1 mM-glucose, but neither agent further increased the level of expression occurring in the presence of a maximally stimulating glucose concentration. The phorbol ester phorbol 12-myristate 13-acetate (PMA) also increased insulin promoter-driven CAT expression in the presence of 1 mM-, but not 11 mM-glucose. Staurosporine blocked the stimulatory effect not only of PMA but also of glucose and of dibutyryl cyclic AMP. We conclude that the 5' upstream region of the insulin gene contains sequences responsible for mediating the stimulatory effect of glucose on insulin-gene transcription.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Control of insulin gene expression by glucose. 132 37

The regulation of expression of the porin genes of Escherichia coli by acid pH was investigated using reporter gene fusions. The ompC-lacZ gene fusion was expressed in response to acidification of the external medium. The kinetics of beta-galactosidase synthesis under acid-induction differed significantly from those obtained under conditions of osmotic stress. The latter led to rapid induction without a lag, followed by establishment of a rate that was equal to the growth rate; acid-induction was frequently preceded by a short lag period, was relatively slow and did not achieve a rate that was in balance with the growth rate. Further, induction of the ompC gene at acid external pH was dependent upon the presence of glucose as sole carbon source; growth with either glycerol or succinate as sole carbon source reduced induction of ompC at acid pH. Osmotic induction was independent of carbon source. The induction of the ompC gene at acid pH was also reduced by addition of cAMP to the growth medium. The porins are known to be subject to catabolite repression and our data are consistent with the exposure to acidic pH resulting in progressive changes in the state of catabolite repression. Acidification of the cytoplasm also provoked a rapid induction of the ompC-lacZ gene fusion. The kinetics of induction resembled the response to osmotic upshock. This response was independent of the identity of the carbon source supplied for growth. The contribution of changes in cytoplasmic pH to the induction of ompC at acid pH is discussed.
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PMID:The regulation of expression of the porin gene ompC by acid pH. 132 70

Deletions which removed rfa genes involved in lipopolysaccharide (LPS) core synthesis were constructed in vitro and inserted into the chromosome by linear transformation. The deletion delta rfa1, which removed rfaGPBI, resulted in a truncated LPS core containing two heptose residues but no hexose and a deep rought phenotype including decreased expression of major outer membrane proteins, hypersensitivity to novobiocin, and resistance to phage U3. In addition, delta rfa1 resulted in the loss of flagella and pili and a mucoid colony morphology. Measurement of the synthesis of beta-galactosidase from a cps-lacZ fusion showed that the mucoid phenotype was due to rcsC-dependent induction of colanic acid capsular polysaccharide synthesis. Complementation of delta rfa1 with rfaG+ DNA fragments resulted in a larger core and restored the synthesis of flagella and pili but did not reverse the deep rough phenotype or the induction of cps-lacZ, while complementation with a fragment carrying only rfaP+ reversed the deep rough phenotype but not the loss of flagella and pili. A longer deletion which removed rfaQGPBIJ was also constructed, and complementation studies with this deletion showed that the product of rfaQ was not required for the functions of rfaG and rfaP. Thus, the function of rfaQ remains unknown. Tandem mass spectrometric analysis of LPS core oligosaccharides from complemented delta rfa1 strains indicated that rfaP+ was necessary for the addition of either phosphoryl (P) or pyrophosphorylethanolamine (PPEA) substituents to the heptose I residue, as well as for the partial branch substitution of heptose II by heptose III. The substitution of heptose II is independent of the type of P substituent present on heptose I, and this results in four different core structures. A model is presented which relates the deep rough phenotype to the loss of heptose-linked P and PPEA.
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PMID:Role of the rfaG and rfaP genes in determining the lipopolysaccharide core structure and cell surface properties of Escherichia coli K-12. 134 43

The oxygen-dependent promoter of the Vitreoscilla hemoglobin (VHb) gene has been shown to be functional in E. coli. Earlier studies established that the promoter is maximally induced under microaerobic conditions and that its activity is also influenced by the cAMP-CAP complex. We demonstrate here that the promoter can be used for regulated, high-level expression of recombinant proteins in two-stage fed-batch fermentations. The promoter is maximally induced at dissolved oxygen levels lower than 5% air saturation. Despite the influence of catabolite repression, glucose and glycerol-containing media give comparable product levels under carbon-limited conditions such as those encountered in typical fed-batch fermentations. The possibility of a third level of control of promoter activity is also indicated. This mode of induction can be repressed by addition of a complex nitrogen source such as yeast extract to the medium. The observed promoter activity can be modulated at least 30-fold over the course of high-cell density fermentations producing either cloned beta-galactosidase or cloned chloramphenicol acetyltransferase (CAT). Densitometer scanning of SDS-polyacrylamide gels revealed that beta-galactosidase was expressed to a level of approximately 10% of total cellular protein.
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PMID:Expression of recombinant proteins in Escherichia coli using an oxygen-responsive promoter. 136 36

A reaction-diffusion model was used to simulate a co-immobilized system utilizing the numerical method of orthogonal collocation. The production of ethanol from deproteinized whey using beta-galactosidase co-immobilized with Saccharomyces cerevisiae in calcium alginate gel beads was chosen as a model system. Calculated concentrations of lactose, glucose, galactose and ethanol were compared with experimental data for a batch reactor and a continuous horizontal packed-bed reactor. The mathematical model has been used to analyse the influence of internal and external mass transfer for the continuous reactor. The external mass transfer was shown to be of minor importance. The introduction of baffles decreased the backmixing in the horizontal packed-bed reactor. Internal mass transfer was found to be the main cause of the reduction in the apparent reaction rate. Thus, much of the expected increase in reaction rate is diminished by mass transfer hindrance when the cell concentration is increased.
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PMID:Simulation of batch and continuous reactors with co-immobilized yeast and beta-galactosidase. 136 20

We report the effects of a strong overexpression of the GAL4 activator protein on the expression of UASGAL regulated genes, obtained by cloning the GAL4 gene and the GAL1-10 upstream activating sequence (UASGAL)-lacZ fusion in the same high copy number plasmid. Comparable amounts of active enzyme were obtained by host strains usually producing different levels of cloned proteins due to their different genetic background. The transformed cells constitutively produced low levels of beta-galactosidase (1-2% of total proteins) both in glucose and in raffinose minimal media. Nevertheless, expression was still inducible and a tenfold induction could be rapidly obtained by the addition of 0.5% (w/v) galactose to the culture, even when glucose was still present in the medium.
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PMID:Enhanced expression of heterologous proteins by the use of a superinducible vector in budding yeast. 136 69


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