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)

The transposon Tn951 (lac) was introduced into the photosynthetic bacterium Rhodopseudomonas sphaeroides 2.4.1, which is normally Lac-, via the P-group plasmid RP1. beta-Galactosidase was produced constitutively in both chemotrophically and phototrophically grown cells, and the levels were found to be the same but low. Mutants were isolated, however, that were able to grow on lactose minimal medium and which expressed different levels of beta-galactosidase when grown chemotrophically or phototrophically. The beta-galactosidase levels found in all R. sphaeroides strains were much less than those found in Escherichia coli.
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PMID:Expression of the transposable lac operon Tn951 in Rhodopseudomonas sphaeroides. 629 Apr 58

Mu d1(Ap lac) was introduced into the photosynthetic bacterium Rhodopseudomonas sphaeroides 2.4.1. via the R-plasmid R751 in an attempt to isolate fusion derivatives involving photosynthetic operons. The selection system is potentially very powerful since R. sphaeroides is normally Lac negative. Among the exconjugants, photosynthesis-deficient mutants were recovered, some of which had elevated beta-galactosidase levels. Among the mutants examined, beta-galactosidase expression was linked exclusively to R751 . Many of the photosynthesis-deficient mutants were found to have alterations in their indigenous plasmids which apparently involved the exchange of DNA from one plasmid to another. Southern blot analysis revealed that there are extensive DNA sequences which are shared by the two plasmids that are involved in the rearrangements and that no exogenous DNA sequences appear to be involved. It was further discovered that plasmid rearrangement is a general phenomenon which can occur spontaneously in R. sphaeroides 2.4.1 and shows a high correlation with a photosynthesis minus phenotype.
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PMID:Plasmid rearrangements in the photosynthetic bacterium Rhodopseudomonas sphaeroides. 632 28

The product of the uvrD gene of Escherichia coli is involved in the repair of DNA damage, mismatch repair, and recombination. Phage Mud(Amp, Lac) was used to form a uvrD-lacZ fusion allowing uvrD expression to be followed by measuring the activity of beta-galactosidase, the product of the lacZ gene. uvrD expression was inducible by DNA damage and was under the control of lexA-recA regulatory system. Mutations in the uvrD gene that result in different phenotypes in respect to DNA repair and spontaneous mutation have been previously found. The phenotype of the uvrD::Mud(Amp, Lac) mutant was mutator and UV-sensitive but not as deficient in host cell reactivation or repair of methyl methanesulfonate damage as the previously described uvrD3 mutant.
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PMID:The Escherichia coli uvrD gene is inducible by DNA damage. 635 63

Under experimental conditions optimal for the assay of D-galactosyl-N-acylsphingosine galactohydrolase (EC 3.2.1.46) activity, homogenates of neurologically normal human brain tissue could transfer galactose from galactosyl ceramide (gal-cer), lactosyl ceramide (lac-cer), 4-methylumbelliferyl-beta-galactoside (4-MU-gal), or p-nitrophenyl-beta-galactoside (PNP-gal) to [1-14C]oleoyl sphingosine, but homogenates of brain tissue from patients with Krabbe's disease lacked this ability. The rate of hydrolysis of ganglioside GM1 and, to a lesser extent, of PNP-gal by homogenates of Krabbe's brain tissue was also decreased. Activity of PNP-beta-galactosidase in normal brain tissue, like that of cerebroside beta-galactosidase from the same source, was considerably more heat-stable than the activity of either 4-MU-beta-galactosidase or the predominant GM1 beta-D-galactosidase (EC 3.2.1.23). Lac-cer and GM1, as well as 4-MU-gal and PNP-gal, were competitive inhibitors of human-brain cerebroside beta-galactosidase. These findings confirm the ability of mammalian cerebroside beta-galactosidase to catalyze a transgalactosylation reaction and provide additional information on the substrate specificity of human brain cerebroside beta-galactosidase.
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PMID:Human brain cerebroside beta-galactosidase: deficiency of transgalactosidic activity in Krabbe's disease. 677 58

Fifty-one mutants of Kluyveromyces lactis that cannot grow on lactose (Lac-) were isolated and characterized. All the mutations are in nuclear genes, are recessive in their wild-type allele and define seven complementation groups, which we designate lac3 through lac9. Strains bearing mutations in lac3, lac5, lac7, lac8 and lac9 are also unable to grow on galactose (Gal-). Since the Gal- and Lac- phenotype co-segregate, they are probably due to a single mutation. Strains bearing mutations in any of the seven complementation groups grow normally on glucose. However, strains bearing mutations in lac3, lac5 and lac6 do not grow on glucose if lactose is also present in the medium. Likewise, strains bearing mutations in lac3 and lac5 do not grow on glucose in the presence of galactose. Complementation groups lac4 and lac5 are loosely linked and map within a cluster of auxotrophic mutations on a chromosome that we designate chromosome 2. The remaining five groups are unlinked. Thus, there is no evidence for clustering of Lac genes into an operon-like regulatory unit.--To further characterize the nature of the Lac- phenotype, the basal and inducible level of beta-galactosidase activity were measured. All mutants had nearly normal basal enzyme levels, except those in lac4, which had barely detectable levels. Inducible enzyme levels varied from barely detectable levels in mutants bearing lac4 mutations up to four-fold inducible levels in strains bearing mutations in other complementation groups. In all cases, however, induction levels were below the 30-fold level obtained in wild-type cells. Three strains bearing lac5 mutations contain increased enzyme activity in the absence of inducer, indicating constitutive synthesis of beta-galactosidase. In summary, these data indicate that several genes are necessary for synthesis of beta-galactosidase activity.
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PMID:Mutations affecting synthesis of beta-galactosidase activity in the yeast Kluyveromyces lactis. 678 84

A hybrid beta-galactosidase molecule containing a substantial portion of the amino-terminal sequence of the maltose-binding protein is inserted in the cytoplasmic membrane of E. coli; in this location, the protein has very low enzymatic activity. The strain producing it is, therefore, Lac-. Selection for derivatives of the fusion strain that are able to grow on lactose yields mutants in which the hybrid protein has become cytoplasmic, and thus has higher enzymatic activity. Among such derivatives, we have isolated a temperature-sensitive conditional lethal mutant that accumulates the precursor of the maltose-binding protein in the cytoplasm, and also accumulates precursors of alkaline phosphatase, lambda receptor protein and the ompF gene gene product. A number of periplasmic proteins are, however, properly localized at the nonpermissive temperature. The temperature-sensitive lesion has been genetically mapped to 2.5 min on the E. coli map, within or near a cluster of genes responsible for cell division and septation. The principle behind the genetic selection employed here should be useful in obtaining other secretion mutants to characterize the cell's secretion machinery.
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PMID:E. coli mutant pleiotropically defective in the export of secreted proteins. 702 50

Somite-derived skeletal myoblasts are supposed to be the sole source of muscle fibre nuclei during pre- and postnatal development, but evidence is accumulating for unorthodox contributions to muscle fibre nuclei from other cell types. For example, in tissue culture, fibroblasts can fuse with dysgenic myoblasts and restore correct membrane function. We report here the results of a series of experiments investigating this phenomenon and its possible mechanism. 10T1/2 cells, infected with a replication defective retrovirus encoding the bacterial enzyme beta-galactosidase, fused to form beta-galactosidase positive, differentiated myotubes when cocultured with differentiating uninfected C2C12 or primary myogenic cells, but this did not occur when they were cocultured with other cells such as 3T3 fibroblasts or PC12 pheochromocytoma cells. Myogenic conversion ranged from 1 to 10% of the 10T1/2 cell population and required close cell interaction between the different cells types: it was not induced by conditioned medium or extracellular matrix deposited by C2C12 cells. Myogenic conversion was also observed in vivo, after injection of similarly infected 10T1/2 cells into regenerating muscle. Conversion was seen also after coculture of uninfected 10T1/2 cells with primary chick myoblasts, thus demonstrating that it was not dependent upon viral infection and that there is no species or class barrier in this phenomenon. Primary fibroblasts, isolated from different organs of transgenic mice carrying a Lac Z marker under the control of a muscle-specific promoter, restricting beta-galactosidase expression to striated muscle cells, also underwent myogenic conversion, when cocultured with C2C12 myoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Myogenic conversion of mammalian fibroblasts induced by differentiating muscle cells. 759 14

The liver is an attractive target tissue for gene therapy. Current approaches for hepatic gene delivery include retroviral and adenoviral vectors, liposome/DNA, and peptide/DNA complexes. This study describes a technique for direct injection of DNA into liver that led to significant gene expression. Gene expression was characterized in both rats and cats following injection of plasmid DNA encoding several different proteins. Luciferase activity was measured after injection of plasmid DNA encoding the luciferase gene (pCMVL), beta-galactosidase (beta-Gal) activity was evaluated in situ using plasmid DNA encoding Lac Z (pCMV beta), and serum concentration of secreted human alpha-1-antitrypsin was measured following injection of plasmid DNA encoding this protein (pRC/CMV-sHAT). Several variables, including injection technique, DNA dose, and DNA diluent, were investigated. Direct injection of pCMVL resulted in maximal luciferase expression at 24-48 hr. beta-Gal staining demonstrated that the majority of transfected hepatocytes were located near the injection site. Significant concentrations of human alpha-1-antitrypsin were detected in the serum of animals injected with pRC/CMV-sHAT. These findings demonstrate the general principle that direct injection of plasmid DNA into liver can lead to significant gene expression.
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PMID:Gene expression following direct injection of DNA into liver. 771 Nov 40

Lactococcus lactis subsp. lactis CNRZ 1123, a Lac- derivative of CNRZ 1122 was transformed by electroporation with the Lactobacillus casei ATCC 393 plasmid pLZ15, which bears a beta-galactosidase gene. The transformants expressed a constitutive beta-galactosidase activity at a higher level than in Lact. casei, and in the cell-free extract two additional protein bands were detected by SDS-PAGE which could correspond to lactose metabolism enzymes. Both plasmid and beta-gal activity were stable in Lactococcus after 100 generations in glucose-containing medium.
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PMID:Expression of Lactobacillus casei ATCC 393 beta-galactosidase encoded by plasmid pLZ15 in Lactococcus lactis CNRZ 1123. 776 47

The binding of Escherichia coli heat-labile enterotoxin (LT) type I to glycosylated proteins with lactose (Gal beta 1-4Glc) by amino carbonyl reaction was studied by the Western blot assay and by the microtiter well binding assay. LT bound to a lactose-alpha-lactalbumin amino carbonyl product (Lac-LA), whereas cholera toxin did not. The binding ability of Lac-LA was abolished by beta-galactosidase treatment, indicating that the terminal galactose is essential for the binding of LT. The binding of LT to Lac-LA was inhibited by galactose and lactose, and most effectively inhibited by lactulose (Gal beta 1-4Fru), which is a structural analog of the Amadori rearrangement product of the amino carbonyl reaction between lactose and an epsilon-amino group of a lysine residue (lactuloselysine). The results suggest that LT recognizes the portion of lactuloselysine in Lac-LA. LT also bound to a melibiose (Gal alpha 1-6Glc)-alpha-lactalbumin amino carbonyl product (Mel-LA), but the binding ability of Mel-LA was weaker than that of Lac-LA, suggesting that the beta 1-4 linked terminal galactose is dispensable but preferable for the binding. Furthermore, LT bound to the amino carbonyl products of lactose with beta-lactoglobulin, caseins, bovine serum albumin, and ovalbumin. These results indicate that LT binds to the amino carbonyl products between proteins and sugars containing the terminal galactose, such as lactose.
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PMID:Escherichia coli heat-labile enterotoxin binds to glycosylated proteins with lactose by amino carbonyl reaction. 793 45


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