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)

In order to establish alternatives to the frequently used uterotropic assay with mice, defined estrogen-sensitive cell lines (MCF-7 cells and LeC-9 cells) were used to determine the estrogenic activities of purified compounds of vegetable origin (myco- and phytoestrogens) and zearalenone-contaminated forage cereals (wheat, barley and oats). In MCF-7 cells, a human breast cancer cell line, the induction of an estrogen-specific exoprotein served as a parameter of estrogenic activities. LeC-9 cells represent a genetically transformed cell clone derived from mouse L-cells. Here, hormone-like activities were measured by the expression of the bacterial chloramphenicol acetyltransferase (CAT) gene under the control of an estrogen-responsive element. Toxic effects affecting cell viability were monitored in this system by the expression of a second reporter gene (the bacterial beta-galactosidase gene controlled by the constitutive human beta-actin promoter). Relative estrogenic activities of myco- and phytoestrogens determined with both systems are concomitant, but higher as compared to the uterotropic assay with mice.
Toxicology 1992 Sep
PMID:Validation of two in vitro test systems for estrogenic activities with zearalenone, phytoestrogens and cereal extracts. 138 42

Tammar wallaby (Macropus eugenii) mammary glands contain a UDP-GlcNAc:Gal beta 1----3Gal beta 1----4Glc beta 1----6-N-acetylglucosaminyltransferase (GlcNAcT) whose activity has been characterized with respect to the effect of pH, apparent Km for acceptor, effects of bivalent metal ions, acceptor specificity and identity of products. The enzyme did not show an absolute requirement for any bivalent metal ion but its activity was increased markedly by Mg2+, Ca2+ and Ba2+ and, to a lesser extent, by Mn2+. When Gal beta 1----3Gal beta 1----4Glc was used as acceptor, the product was Gal beta 1----3[GlcNAc beta 1----6]Gal beta 1----4Glc. With Gal beta 1----3Gal beta 1----3Gal beta 1----4Glc as acceptor, the product was shown, by 1H-NMR spectroscopy and exo-beta-galactosidase digestion, to be a novel pentasaccharide with the structure Gal beta 1----3[GlcNAc beta 1----6]Gal beta 1----3Gal beta 1----4Glc, suggesting that the enzyme recognises the non-reducing end of the acceptor substrate, rather than the reducing end.
Biochim Biophys Acta 1992 Sep 15
PMID:Biosynthesis of marsupial milk oligosaccharides. II: Characterization of a beta 6-N-acetylglucosaminyltransferase in lactating mammary glands of the tammar wallaby, Macropus eugenii. 138 55

We have developed a set of three cloning vectors for the expression of polypeptides on the surface of the M13 viral coat. The M13mp8 genome has been engineered for expression of foreign protein sequences near the NH2-terminus of the mature pIII protein, which is present in five copies on the outside of each M13 viral particle. All three of the vectors carry the same two useful restriction sites for directed cloning of inserts in the pIII coding region; in addition, one vector carries the bacterial gene conferring resistance to the antibiotic tetracycline, and another expresses the lacZ' polypeptide that allows functional complementation of beta-galactosidase activity within the host bacterial cell. All of these vectors propagate well in E. coli DH5 alpha F' cells and do not require helper phage. We demonstrate that a bacteriophage, expressing an eleven amino acid epitope (from human c-myc) at the NH2-terminus of pIII in one of our vectors, can be purified from a vast mixture of other M13 phage through panning techniques. In particular, we find that the c-myc-expressing viral particles can be easily recovered from phage mixtures with the biotinylated form of the monoclonal antibody, 9E10, and streptavidin-coated MagneSphere beads.
Biotechniques 1992 Sep
PMID:Multipurpose vectors for peptide expression on the M13 viral surface. 138 74

Although some protein folding theories sustain that the peptides (loops) that connect elements of more compact secondary structure may be important in the folding process, most of the data accumulated until now seems to contradict this notion. To approach this problem we have isolated and characterized a number of mutants in which the amino acid sequence of the peptide that connects helix D and helix E in the H-chain of human ferritin has been randomized. Our results indicate that, though no single loop residue is absolutely required for ferritin to attain the native conformation, most of the mutants that we have obtained by random regional mutagenesis, affect its folding/assembly process. This conclusion was reached utilizing a sensitive test that associates the color formed by a colony synthesizing a hybrid ferritin-beta-galactosidase protein to the ability of the ferritin domain to fold and assemble as the native protein. The characterization of the folding/assembly properties of our collection of mutants and the comparison of the mutant loop sequences, have allowed us to draw the following conclusions. Mutants that have positively charged residues at position 159, 160 or 161 fail to assemble into the native protein shell and form an insoluble aggregate. Interestingly some loop amino acid sequences cause the E-helix to reverse direction and to expose its COOH group, normally hidden inside the protein cavity, to the solvent. The propensity of a given ferritin mutant to fold into this "non-native" conformation can be attenuated by the introduction of Gly at position 159 and 164, as in the natural ferritin.
J Mol Biol 1992 Sep 20
PMID:Loop mutations can cause a substantial conformational change in the carboxy terminus of the ferritin protein. 140 67

The synergistic effects of dexamethasone (DEX) and thyroxine (T4) on the postnatal maturation of the 13-d-old rodent small intestine has been studied. Previous studies have shown that hydrocortisone and T4 produced a synergistic response in enzyme maturation. However, T4 elevates corticosteroid-binding globulin, which reduces the clearance of hydrocortisone. Thus, the apparent synergy between T4 and hydrocortisone may have been due to increased glucocorticoid availability. DEX, which does not bind to corticosteroid-binding globulin, was given (d8-12) at 25 pmol (i.e. 0.01 micrograms)/g body wt/d as established by a dose-response study in which this dose of DEX induced one third the maximum response in sucrase activity. In this way, synergy with T4 (130 pmol/g body wt/d, i.e. 0.1 micrograms/g body wt/d, d 5-12) could still be observed. Glucoamylase, lactase, acid beta-galactosidase, alkaline phosphatase, and sucrase activities were determined in two regions of the small intestine. Overall, the results for the two hormones administered alone showed intestinal maturation to be not significantly affected in the T4 group and partially stimulated in the DEX group. When combined, DEX + T4 synergistically increased jejunal sucrase, ileal glucoamylase, and duodenal alkaline phosphatase, and lowered ileal acid beta-galactosidase. The striking exceptions to the general pattern were two brush border enzymes that normally decline during intestinal maturation, namely ileal alkaline phosphatase and jejunal and ileal lactase. For these enzymes, DEX alone did not elicit precocious maturation, and there was no evidence for a synergistic interaction of these two hormones. Serum corticosterone concentrations also were measured. When corticosterone concentrations were compared with enzyme activity, no correlation was found.(ABSTRACT TRUNCATED AT 250 WORDS)
Pediatr Res 1992 Sep
PMID:Synergistic effects of thyroxine and dexamethasone on enzyme ontogeny in rat small intestine. 140 67

Expression of the rpoBC genes encoding the beta and beta' RNA polymerase subunits of Escherichia coli is autogenously regulated. Although previous studies have demonstrated a post-transcriptional feedback mechanism, complex transcriptional controls of rpoBC expression may also contribute. We show that an attenuator (rpoBa) separating the ribosomal protein (rpl) genes from the rpoBC genes in the rplKAJLrpoBC gene cluster is modulated in its efficiency in response to changes in the frequency of transcription initiated by promoters located upstream. A series of rplJLrpoBalacZ transcriptional fusions was constructed on lambda vectors in which transcription into the rpoBa attenuator was varied by using a variety of promoters with different strengths. beta-galactosidase assays performed on monolysogens of the recombinant phage show that with transcription increasing over a 40-fold range, readthrough of rpoBa decreases from 61% to 19%. In contrast, two other well-characterized terminators show nearly constant efficiencies over a similar range of transcription frequencies. Using a set of phage P22 ant promoter variants with single-nucleotide changes in the promoter consensus sequences also demonstrates that the modulation of rpoBa function appears to be unrelated to the phenomenon of 'factor-independent antitermination' reported by others. The implications for autogenous control of RNA polymerase synthesis are discussed.
Nucleic Acids Res 1992 Sep 25
PMID:Transcription frequency modulates the efficiency of an attenuator preceding the rpoBC RNA polymerase genes of Escherichia coli: possible autogenous control. 140 90

Kinetic parameters for the hydrolysis of a series of deoxy and deoxyfluoro analogues of 2',4'-dinitrophenyl beta-D-galactopyranoside by Escherichia coli (lacZ) beta-galactosidase have been determined and rates found to be two to nine orders of magnitude lower than that for the parent compound. These large rate reductions result primarily from the loss of transition-state binding interactions due to the replacement of sugar hydroxy groups, and such interactions are estimated to contribute at least 16.7 kJ (4 kcal).mol-1 to binding at the 3, 4 and 6 positions and more than 33.5 kJ (8 kcal).mol-1 at the 2 position. The existence of a linear free-energy relationship between log(kcat./Km) for these compounds and the logarithm of the first-order rate constant for their spontaneous hydrolysis demonstrates that electronic effects are also important and provides direct evidence for oxocarbonium ion character in the enzymic transition state. A covalent intermediate which turns over only extremely slowly (t1/2 = 45 h) accumulates during hydrolysis of the 2-deoxyfluorogalactoside, and kinetic parameters for its formation have been determined. This intermediate is nonetheless catalytically competent, since it re-activates much more rapidly in the presence of the transglycosylation acceptors methanol or glucose, thereby providing support for the notion of a covalent intermediate during hydrolysis of the parent substrates.
Biochem J 1992 Sep 15
PMID:Binding energy and catalysis. Fluorinated and deoxygenated glycosides as mechanistic probes of Escherichia coli (lacZ) beta-galactosidase. 141 31

The regulation of Shiga toxin expression in a clinical isolate of S. dysenteriae 1 by the Fe-Fur (Iron-ferric uptake regulatory protein) repressor complex was investigated. The presence of an endogenous Fur repressor protein capable of binding to either a Fur binding consensus sequence or the regulatory region of SLT-1A was determined in toxinogenic strains of S. dysenteriae. Plasmid constructs bearing Fur binding sites fused to readily assayable reporter genes were used. Plasmid pSC27.1 contains a 21 bp synthetic oligonucleotide Fur protein binding consensus sequence located upstream to the gene for beta-galactosidase. Plasmid pSC105 contains the regulatory sequences of Shiga-like toxin-1A located upstream to the gene for alkaline phosphatase. In an analogous fashion to Shiga toxin regulation in S. dysenteriae 1, transformants bearing either pSC27.1 or pSC105 plasmid DNA were repressed in gene product expression when grown in minimal medium supplemented with iron. Conversely, transformants were de-repressed when grown under iron limiting conditions. These data suggest the presence of Fe-Fur mediated regulation of toxinogenesis in clinical isolates of S. dysenteriae.
J Diarrhoeal Dis Res 1992 Sep
PMID:Regulation of the SLT-1A toxin operon by a ferric uptake regulatory protein in toxinogenic strains of Shigella dysenteriae type 1. 143 Sep 67

A fusion gene containing 3 kilobases of human proenkephalin 5'-flanking sequences and 1 kilobase of human proenkephalin 3'-flanking sequence and the easily visualized histochemical marker, Escherichia coli beta-galactosidase, was used to study the function of cis-regulatory elements within the human proenkephalin gene in transgenic mice. Here data are presented on expression and regulation of this fusion gene in the reproductive system of three independent lines of transgenic mice. Within the male reproductive system, the fusion gene is expressed in the proximal epididymis and in developing germinal cells but not in mature or elongating spermatids. In the female reproductive system, the transgene was expressed at low basal levels, but expression was dramatically stimulated in the ovary and oviduct by hormonal stimulation and pregnancy; additionally, expression was induced at the uteroplacental junction in pregnant mice. Taken together these observations suggest that critical sequences for expression and regulation of the proenkephalin gene within the reproductive system are contained within sequences of the construct.
Mol Endocrinol 1992 Sep
PMID:Expression and regulation of a proenkephalin beta-galactosidase fusion gene in the reproductive system of transgenic mice. 143 91

Crude extracts of Babesia bovis parasites were shown to induce levels of protection in susceptible cattle equivalent to that resulting from natural infection. The crude material was systematically fractionated and tested in numerous sequential vaccination/challenge experiments in adult cattle. Antigens in protective fractions were then purified by affinity chromatography with monoclonal antibodies. Three highly protective (more than 95% reduction in parasitaemias) antigens were thus identified. None of these antigens was immunodominant; a number of immunodominant antigens were identified and all were immunosuppressive and/or non-protective. The three protective antigens were cloned and expressed as either beta-galactosidase or glutathione-S-transferase (GST) fusion proteins. Two of these, GST-12D3 and GST-11C5, when used in combination were almost as protective as has been previously shown for the commercially available live attenuated vaccine. A short fragment of a third antigen (21B4) has also been shown to be protective. In two of the antigens, repetitive segments have been shown to be non-protective while the third antigen (12D3) does not contain repetitive domains. Homologues of these antigens exist in other Babesia species and it is anticipated that these may be candidate antigens for protective vaccines against those species.
Vet Parasitol 1992 Sep
PMID:The development of a recombinant Babesia vaccine. 144 Nov 89


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