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)

Beggs, William H. (University of Minnesota, Minneapolis), and Palmer Rogers. Galactose repression of beta-galactosidase induction in Escherichia coli. J. Bacteriol. 91:1869-1874. 1966.-Galactose repression of beta-galactosidase induction in Escherichia coli was investigated to determine whether the galactose molecule itself is the catabolite repressor of this enzyme system. Without exception, beta-galactosidase induction by cells grown in a synthetic salts medium with lactate or glycerol as the carbon source was more strongly repressed by glucose than by galactose. This relationship existed even when the organism was previously grown in the synthetic medium containing galactose as the source of carbon. Two observations suggested that the ability of galactose to repress beta-galactosidase formation by Escherichia coli depends directly upon the cells' capacity to catabolize galactose. First, galactose repression of beta-galactosidase synthesis was markedly enhanced in bacteria tested subsequent to gratuitous induction of the galactose-degrading enzymes with d-fucose. Second, galactose failed to exert a repressive effect on beta-galactosidase in a galactose-negative mutant lacking the first two enzymes involved in galactose catabolism. Glucose completely repressed enzyme formation in this mutant. This same mutant, into which the genes for inducible galactose utilization had been introduced previously by transduction, again exhibited galactose repression. Pyruvate was found to be at least as effective as galactose in repressing beta-galactosidase induction by cells grown in synthetic salts medium plus glycerol. It is concluded that the galactose molecule itself is not the catabolite repressor of beta-galactosidase, but that repression is exerted through some intermediate in galactose catabolism.
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PMID:Galactose repression of beta-galactosidase induction in Escherichia coli. 532 10

Paigen, Kenneth (Roswell Park Memorial Institute, Buffalo, N.Y.). Role of the galactose pathway in the regulation of beta-galactosidase. J. Bacteriol. 92:1394-1403. 1966.-Galactose and its metabolites, galactose-1-phosphate, uridine diphosphogalactose, and uridine diphosphoglucose, as well as metabolites derived from uridine diphosphoglucose, were tested for their role in the regulation of beta-galactosidase. In cultures of wild-type Escherichia coli strains K-12 and B, exogenous galactose was no more effective as a repressor than were other carbon sources. Exogenous galactose also did not repress beta-galactosidase when added to mutants which can accumulate intracellular galactose or galactose-1-phosphate, indicating that these compounds do not repress. In such strains, repression of beta-galactosidase formation did occur if galactose was added in the presence of another metabolizable carbon source. This repression is presumably a consequence of the growth inhibition which follows the accumulation of these compounds, and the general catabolite repression which develops during growth inhibition. Exogenous galactose did repress beta-galactosidase in a mutant which accumulates uridine diphosphogalactose. This appears to result from a combination of several factors. These include a general inhibition of protein synthesis through depletion of the uridine triphosphate pool, catabolite inhibition as a consequence of growth inhibition, as well as a specific inhibition of beta-galactosidase formation. Glucose repression of beta-galactosidase was normal in a mutant strain blocked in the formation of uridine diphosphoglucose from uridine triphosphate and glucose-1-phosphate, indicating that neither uridine diphosphoglucose nor any compound uniquely derived from it functions as the hypothetical catabolite repressor. It is concluded that at least two separate mechanisms exist for the endogenous repression of beta-galactosidase in E. coli. One is exerted by uridine diphosphogalactose or its metabolic product; the other, by the generalized catabolite repressor which is still formed in strains unable to make uridine diphosphogalactose or uridine diphosphoglucose.
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PMID:Role of the galactose pathway in the regulation of beta-galactosidase. 533 1

THE METABOLISM OF LACTOSE WAS FOUND TO BE CONTROLLED BY THREE GENES: a gene for the synthesis of a beta-galactosidase attacking only phosphorylated galactosides; a gene for a protein permitting concentration of phosphorylated galactosides which probably acts by transferring phosphates to them; and a gene regulating the first two structural genes. The three genes are closely linked and may have the same order as in Escherichia coli. Galactose-6-phosphate was found to be a better inducer of lactose utilization than is galactose or any other inducer. The inhibition of induction by isopropylthiogalactoside was found to occur at the level of the protein permitting the concentration of galactoside phosphates.
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PMID:Metabolism of lactose by Staphylococcus aureus and its genetic basis. 566 99

The GAL1 and GAL10 genes, separated by 680 base pairs and divergently transcribed on chromosome 2 of Saccharomyces cerevisiae, were separately fused to the lacZ gene of Escherichia coli so that beta-galactosidase synthesis in S. cerevisiae reflected GAL1 and GAL10 promoter function. Analysis of two sets of deletions defined a 75-base-pair sequence, located ca. midway between the transcription initiation regions of GAL1 and GAL10, that mediates GAL4-dependent induction of both genes. Deletion of various parts of this sequence (called the GAL upstream activating sequence or UASG) reduced GAL1 and GAL10 induction about equally. Sequences in the GAL10-proximal half of UASG in some sequence contexts functioned independently of sequences in the GAL1-proximal half of UASG. A 33-base-pair deletion of the GAL10-proximal half of UASG drastically reduced induction. Deletions between UASG and the GAL1 TATA box caused beta-galactosidase to be synthesized at an unexpectedly high basal level, that is, in the absence of galactose and GAL4 product. Some of these mutations also reduced the repression caused by glucose.
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PMID:Saccharomyces cerevisiae GAL1-GAL10 divergent promoter region: location and function of the upstream activating sequence UASG. 639 52

beta-Galactosidase from Alternaria tenius was purified to homogeneity from the cultural fluid using acetone precipitation, ion-exchange chromatography on DEAE-cellulose, adsorption on hydroxylapatite and affinity chromatography on N-(beta-D-galactopyranosyl-thiocarbamoyl)-beta-aminocaproyl-AN-Sepharose 4B. The enzyme homogeneity was demonstrated by ultracentrifugation and polyacrylamide gel electrophoresis with SDS or without it. The specific activity of the homogeneous enzyme is 160 u. per mg of protein; mol. weight as determined by various methods is 142 000-176 000, pI = 4.6, temperature optimum is 60-65 degrees, pH optima for o-nitrophenyl-beta-D-galactopyranoside (o-NPG) and lactose are 3.8--4.4 and 3.6--4.8, respectively. The Km values for o-NPG and lactose are 0.21 . 10(-3) and 6.57 . 10-3 M, respectively. The enzyme is a glycoprotein and contains up to 30% of carbohydrates. EDTA and pCMB have no effect on the beta-galactosidase activity. Galactose acts as a competitive inhibitor, while glucose has no inhibiting effect on the enzyme activity.
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PMID:[Purification and properties of beta-galactosidase from Alternaria tenius]. 679 53

ebg enzyme, the second beta-galactosidase of Escherichia coli, does not normally convert lactose into an inducer of the lac operon. We previously reported the existence of a mutant ebg enzyme that does make such an inducer in vivo (Rolseth et al., J. Bacteriol. 142:1036-1039, 1980). Here I report that the mutant enzyme makes inducer from lactose in vitro and that the inducer is allolactose. Allolactose is made from lactose by direct transgalactosylation at a rate that is 8 to 10% of the rate of lactose hydrolysis. Galactose is also transferred to glucose free in solution, but the resulting indirect transgalactosylation products are not allolactose or lactose. The ability to efficiently synthesize allolactose is a general property of class IV mutant ebg enzymes, whereas other classes of ebg mutant enzymes are unable to synthesize allolactose efficiently. The evolutionary implications of this new function are discussed.
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PMID:Transgalactosylation activity of ebg beta-galactosidase synthesizes allolactose from lactose. 680 Oct 19

1. myo-Inositol was galactosylated by UDP-galactose in the presence of alpha-lactalbumin plus rat mammary Golgi membranes enriched in galactosyltransferase (EC 2.4.1.22). 2. The isolated product migrated on GLC as two peaks of material, apparently identical to galactinol (galactosylinositol) isolated from rat milk. 3. These findings make it likely that in vivo lactose synthetase is responsible for converting inositol into galactinol within the Golgi lumen. 4. This is consistent with the ability of inositol to penetrate the Golgi membrane in vitro, and renders less likely a previously proposed role of beta-galactosidase (EC 3.2.1.23) in mammary galactinol synthesis.
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PMID:Biosynthesis of galactinol by lactose synthetase. 680 5

Previous studies using in vitro procedures have not clearly established whether the estrogen receptor (ER) acts as a monomer or dimer in the cell. We have used the yeast two-hybrid system as an in vivo approach to investigate the dimerization of the estrogen receptor in the absence and presence of estrogen and anti-estrogens. This system is independent of ER binding to the estrogen response element. Two vectors, expressing GAL4 DNA binding domain-human ER and GAL4 transactivation domain-human ER, were constructed. Control experiments showed that each fusion protein had a high affinity binding site for estradiol-17 beta and could transactivate an ERE-LacZ reporter gene in yeast similar to the wild type ER. The two fusion proteins, GAL4 DB-hER and GAL 4 TA-hER, were expressed in the yeast strain, PCY2, which carries a GAL1 promoter-lacZ reporter. ER dimerization was measured via reconstitution of GAL4 through interaction of the fusion proteins, which transactivates LacZ through the GAL1 promoter. When both ER fusion proteins were expressed, beta-galactosidase activity was estradiol-17 beta-inducible. Furthermore, we showed that both tamoxifen and ICI 182,780 also induced beta-galactosidase activity, albeit lower than that induced by estradiol-17 beta. These results strongly argue that ER dimerization is ligand-dependent and the dimer can be induced by estradiol-17 beta, tamoxifen, or ICI 182,780. We also treated the yeast containing the two fusion proteins with estradiol-17 beta and tamoxifen or ICI 182,780 simultaneously to determine the effects on ER dimerization. beta-Galactosidase activity was lower when the yeast was treated with a higher ratio of tamoxifen or ICI 182,780 to estrogen than estradiol-17 beta alone. Taken together, we conclude that ER dimerization is ligand (estradiol-17 beta, tamoxifen, or ICI 182, 780)-dependent, and we suggest that estradiol-17 beta-induced dimers are destabilized when estradiol-17 beta is used with tamoxifen or ICI 182,780 simultaneously.
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PMID:Yeast two-hybrid system demonstrates that estrogen receptor dimerization is ligand-dependent in vivo. 755 88

In vivo gene transfer by lipofection was studied in the mouse lung to develop a gene therapy protocol for disorders in which the lung is affected, such as cystic fibrosis. The bacterial lacZ gene encoding beta-galactosidase was used as a reporter, and the X-GAL staining procedure was optimized for cryostat sections of mouse lung. Three to five days after intratracheal instillation of a lacZ DNA-liposome mixture, lacZ expression was shown in a high percentage of airway epithelium cells. The staining proved to be restricted mainly to the epithelium of the bronchi.
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PMID:In vivo transfer and expression of the lacZ gene in the mouse lung. 768 73

The advantages of gratuitous induction for GAL-regulated cloned gene (lacZ) product synthesis were evaluated for the yeast Saccharomyces cerevisiae. The growth, yield, and productivity of a gratuitous (gal1) strain were compared with those of an otherwise isogenic, nongratuitous (GAL1) strain. Batch studies clearly demonstrated the improvements possible in product synthesis when the inducer is not metabolized by the yeast cells; both beta-galactosidase specific and volumetric activities were superior for the gal1 strain. At equivalent metabolizable sugar concentrations, the productivity of the gratuitous strain exceeded that of the nongratuitous strain by 180%. The effects of initial inducer concentration and induction time were also examined. For the gratuitous strain, galactose:glucose ratios as low as 0.1 still gave maximum beta-galactosidase volumetric activity. A 5-fold higher ratio was necessary for full induction with the nongratuitous strain, and productivity was substantially lower relative to the gal1 strain. A comparison of various times for galactose addition indicated that productivity is highest when the gratuitous culture is induced for the entire batch fermentation.
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PMID:Enhanced productivity through gratuitous induction in recombinant yeast fermentations. 776 24


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