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)

Expression of the Escherichia coli lactose operon in Rhizobium meliloti 104A14 made the cells sensitive to the addition of the beta-galactosides lactose, phenyl-beta-D-galactoside, and lactobionic acid. Growth stopped when the beta-galactoside was added and viability decreased modestly during the next few hours, but little cell lysis was observed and the cells appeared normal. Protein synthesis was not inhibited. Growth was inhibited only when beta-galactosidase expression was greater than 160 U. Lactose-resistant mutants had defects in the plasmid-carried E. coli beta-galactosidase or beta-galactoside permease and in the R. meliloti genome. We speculate that uncontrolled production of galactose by the action of the lactose operon proteins was responsible for growth inhibition.
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PMID:Lactose inhibits the growth of Rhizobium meliloti cells that contain an actively expressed Escherichia coli lactose operon. 642 92

The nucleotide sequence of the lacY gene coding for lactose permease (M protein) in Escherichia coli has been determined. The sequence includes the intergenic regions between the lacZ (beta-galactosidase) and lacY genes as well as the region between the lacY and lacA (transacetylase) genes. Lactose permease is predicted to consist of 417 residues (71% nonpolar), resulting in a protein with a molecular weight of 46,504. The reading frame was confirmed by the sequence of a nonsense mutation changing codon 33 from UGG to UAG.
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PMID:Sequence of the lactose permease gene. 644 53

Several different strains of Escherichia coli were grown on a variety of carbon sources under various growth conditions. Lactose was added (usually at mid-log phase), and the concentrations of the products of beta-galactosidase action on this sugar (galactose, glucose, and allolactose) were determined at various times thereafter in the total culture and in the medium. It was found that with each strain, with all carbon sources, and under all of the conditions studied, a very large proportion of the products were found in the medium. Control studies were carried out which showed that these results were not artifacts of the method of separating the cells from the medium. The results also did not arise from the secretion of beta-galactosidase into the medium, from the diffusion of substrates and products into and out of the cells due to leaks in the membrane, or from faults in the method of sugar analysis. In addition, the results showed that there were very high levels of products inside the cells under the conditions used and that the efflux of the products was rapid. The efflux might be energetically advantageous to the cell as well as being a means of storing excess products until needed.
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PMID:Efflux of beta-galactosidase products from Escherichia coli. 676 83

Lactose is not itself an inducer of the lac operon, nor is it converted to an inducer by ebg+ beta-galactosidase of Escherichia coli. We report here the isolation of a mutant Ebg beta-galactosidase which is capable of converting lactose into an inducer of the lac operon.
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PMID:A mutant Ebg enzyme that converts lactose into an inducer of the lac operon. 676 7

We studied yogurts and industrialized curdled milk in three different storage times, as well as homemade and Syrian curdled milk and cheeses. Lactose content (gm%) and beta-galactosidase activity were determined in these products. Lactose content was elevated in yogurts and curdled milk with a lactose reduction of about 22% compared to the lactose of cow milk, with a mean and standard desviation (M +/- SD) of 3.81 +/- 0.47 gm%. In the cheeses lactose content was low, between 1.91 and 0.03 g%. beta-galactosidase activity was present in yogurts and curdled milk, with values between 0.58 and 3.61 U in time I and M +/- SD of 0.15 +/- 0.23 U. A significant decrease of beta-galactasidase activity was observed during the storage time. By analyzing and comparing these findings with the literature, we conclude that the products studied, by their low content of lactose (cheeses and yakult) or by the presence of beta-galactasidase activity (yogurts and curdled milk at time I) probably would be tolerated by most hipolactasic persons.
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PMID:[Lactose content and beta-galactosidase activity in yogurt, cheeses and curdled milk made in Brazil]. 757 85

A study of the beta-galactosidase produced by the psychrotrophic bacterium Buttiauxella agrestis has been carried out. This micro-organism was isolated from raw milk and the enzyme isolated using standard methods. Molecular mass was estimated to be 515 kDa. The isoelectric point was close to 4.45. Optimum pH was 7.25. Maximal activity was observed at 50 degrees C and activation energy was estimated to be 39.1 kJ mol-1. Lactose enhanced thermal stability. Using p-nitrophenyl-beta-D-galactopyranoside as the substrate, the Km was 11 mumol l-1 and Vmax was 85 U mg-1 protein. beta-Mercaptoethanol and ethanol were inhibitors; glycerol acted as a complex effector. The enzyme required divalent cations for activity while it was inhibited by EDTA. When the enzyme was immobilized in diethyl aminoethylcellulose the optimum pH of activity was 8. Km was 47 mumol l-1 and Vmax was 96 U mg-1 protein.
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PMID:Isolation and properties of free and immobilized beta-galactosidase from the psychorotrophic enterobacterium Buttiauxella agrestis (strain NC4). 761 19

Lactose in yogurt is better absorbed by lactase-deficient subjects than is an equivalent quantity of lactose in milk, presumably because of the microbial activity of the beta-galactosidase present in yogurt. In this study, we describe a process that increases the beta-galactosidase of yogurt 5- to 6-fold and the ability of this high lactase yogurt to enhance lactose absorption in lactase-deficient subjects. These subjects ingested the yogurt meals after a 12-h fast, and lactose malabsorption was determined by measuring breath hydrogen. Breath hydrogen was reduced 39% following ingestion of high lactase yogurt from that after consumption of conventional yogurt, indicating that the high lactase yogurt enhanced lactose absorption. However, the reduction after high lactase yogurt was less than expected, given the 5- to 6-fold increment in beta-galactosidase measured in vitro. In vivo activity of beta-galactosidase requires that the enzyme resist acid denaturation in the stomach. The beta-galactosidase in high lactase yogurt was much less acid resistant than was the beta-galactosidase in conventional yogurt, and the relative inability of high lactase yogurt to enhance lactose absorption was likely due to the destruction of the beta-galactosidase in the stomach.
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PMID:Factors affecting the ability of a high beta-galactosidase yogurt to enhance lactose absorption. 769 33

The main polysaccharide component of the thickened cell walls in the storage parenchyma of Lupinus angustifolius L. cotyledons is a linear (1-->4)-beta-linked D-galactan, which is mobilised after germination (L. A. Crawshaw and J.S.G Reid, 1984, Planta 160, 449-454). The isolation from the germinated cotyledons of a beta-D-galactosidase or exo-(1-->4)-beta-D-galactanase with a high specificity for the lupin galactan is described. The enzyme, purified using diethylaminoethyl-cellulose, carboxymethyl-cellulose and affinity chromatography on lactose-agarose, gave two bands (major 60 kDa, minor 45 kDa) on sodium dodecyl sulphate-gel electrophoresis, and two similar bands on isoelectric focusing (major, pI 7.0, minor pI 6.7, both apparently possessing enzyme activity). The minor component cross-reacted with an antiserum raised against, and affinity-purified on, the major band. Both components had a common N-terminal sequence. The minor component was probably a degradation product of the major one. The enzyme had limited beta-galactosidase action, catalysing the hydrolysis of p-nitrophenyl-beta-D-galactopyranoside and (1-->4)- and (1-->6)-beta-linked galactobioses. Lactose [beta-D-galactopyranosyl-(1-->4)-D-glucose] was hydrolysed only very slowly and methyl-beta-D-galactopyranoside not at all. Lupin galactan was hydrolysed rapidly and extensively to galactose, whereas other cell-wall polysaccharides (xyloglucan and arabinogalactan) with terminal non-reducing beta-D-galactopyranosyl residues were not substrates. A linear (1-->4)-beta-linked galactopentaose was hydrolysed efficiently to the tetraose plus galactose, but further sequential removals of galactose to give the tetraose and lower homologues occurred more slowly. Galactose, gamma-galactonolactone and Cu+2 were inhibitory. No endo-beta-D-galactanase activity was detected in lupin cotyledonary extracts, whereas exo-galactanase activity varied pari passu with galactan mobilisation. Exo-galactanase protein was detected, by Western immunoblotting of cotyledon extracts, just before the activity could be assayed and then increased and decreased in step with the enzyme activity. The exo-galactanase is clearly a key enzyme in galactan mobilisation and may be the sole activity involved in depolymerising the dominant (1-->4)-beta-galactan component of the cell wall.
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PMID:Purification and properties of a novel beta-galactosidase or exo-(1-->4)-beta-D-galactanase from the cotyledons of germinated Lupinus angustifolius L. seeds. 776 18

Strains of Saccharomyces cerevisiae transformed with a yeast multicopy expression vector carrying the cDNA for Aspergillus niger secretory beta-galactosidase under the control of ADH1 promoter and terminator were studied for their fermentation properties on lactose (V. Kumar, S. Ramakrishnan, T. T. Teeri, J. K. C. Knowles, and B. S. Hartley, Biotechnology 10:82-85, 1992). Lactose was hydrolyzed extracellularly into glucose and galactose, and both sugars were utilized simultaneously. Diauxic growth patterns were not observed. However, a typical biphasic growth was observed on a mixture of glucose and galactose under aerobic and anaerobic conditions with transformants of a haploid S. cerevisiae strain, GRF167. Polyploid distiller's yeast (Mauri) transformants were selected simply on the basis of the cloned gene expression on X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) plates. Rapid and complete lactose hydrolysis and higher ethanol (0.31 g/g of sugar) and biomass (0.24 g/g of sugar) production were observed with distiller's yeast grown under aerobic conditions. A constant proportion (10%) of the population retained the plasmid throughout the fermentation period (48 h). Nearly theoretical yields of ethanol were obtained under anaerobic conditions on lactose, glucose, galactose, and whey permeate media. However, the rate and the amount of lactose hydrolysis were lower under anaerobic than aerobic conditions. All lactose-grown cells expressed partial galactokinase activity.
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PMID:Fermentation of lactose by yeast cells secreting recombinant fungal lactase. 828 14

A sandwich-type flow-injection binding assay for quantitation of various IgG's was developed. The assay is based on the pseudoimmunological reaction between protein A from Staphylococcus aureus and immunoglobulin G from different species. Protein A immobilized on a solid support and a fusion protein of protein A and beta-galactosidase from Escherichia coli are used for detection. The fusion protein is produced with a temperature-inducible recombinant E. coli strain. A sandwich is formed by subsequent injection of IgG and fusion protein into the buffer stream flowing through the immobilized protein A column. The amount of enzyme activity bound is proportional to the amount of IgG bound and is measured by pumping a lactose solution as substrate for beta-galactosidase through the protein A column. Lactose is converted to glucose and galactose. The detector is an enzyme thermistor that measures the heat evolved in the enzymatic conversion of glucose by coimmobilized glucose oxidase and catalase. The assay takes 16 min at a flow rate of 0.6 mL min-1 with a lower detection limit of 33 pmol per injection of rabbit IgG. The precision of replicate measurements has a standard deviation of 4-5%, and the column can be used for more than 50 cycles.
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PMID:Specific flow injection sandwich binding assay for IgG using protein A and a fusion protein. 829 25


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