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)

Beta-galactosidase is an enzyme administered as a digestive supplement to treat lactose intolerance, a genetic condition prevalent in most world regions. The gene encoding an acid-stable beta-galactosidase potentially suited for use as a digestive supplement was cloned from Aspergillus niger van Tiegh, sequenced and expressed in Pichia pastoris. The purified recombinant protein exhibited kinetic properties similar to those of the native enzyme and thus was also competitively inhibited by its product, galactose, at application-relevant concentrations. In order to alleviate this product inhibition, a model of the enzyme structure was generated based on a Penicillium sp. beta-galactosidase crystal structure with bound beta-galactose. This led to targeted mutagenesis of an Asp(258)-Ser-Tyr-Pro-Leu-Gly-Phe amino acid motif in the A. niger van Tiegh enzyme and isolation from the resultant library of a mutant beta-galactosidase enzyme with reduced sensitivity to inhibition by galactose (K (i) of 6.46 mM galactose, compared with 0.76 mM for the wildtype recombinant enzyme). The mutated enzyme also exhibited an increased K (m) (3.76 mM compared to 2.21 mM) and reduced V (max) (110.8 micromol min(-1) mg(-1) compared to 172.6 micromol min(-1) mg(-1)) relative to the wild-type enzyme, however, and its stability under simulated fasting gastric conditions was significantly reduced. The study nevertheless demonstrates the potential to rationally engineer the A. niger van Tiegh enzyme to relieve product inhibition and create mutants with improved, application-relevant kinetic properties for treatment of lactose intolerance.
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PMID:Engineering of a fungal beta-galactosidase to remove product inhibition by galactose. 2049 47

Throughout the reproductive lifespan of most male mammals, sperm production is constant because of the regulated differentiation of spermatogonia. Retinoic acid (RA) and a downstream target, Stra8, are required for complete spermatogenesis. To examine the role of RA in initiating spermatogonial differentiation, a transgenic mouse model expressing beta-galactosidase under the control of an RA response element was used. Cells in the neonatal testis undergoing active RA signaling were visualized by beta-galactosidase activity, the relationship between RA and differentiation determined, and the role of RA-degrading enzymes in regulating RA demonstrated. Beta-galactosidase activity was found to be predominantly associated with differentiating, premeiotic germ cells and to be distributed nonuniformly throughout the seminiferous tubules. Additionally, beta-galactosidase activity in premeiotic germ cells colocalized with STRA8 protein and was induced in germ cells with exogenous RA treatment. The RA-degrading enzyme, CYP26B1, was found to have germ cell localization and nonuniform distribution between tubules via immunohistochemistry. Treatment with a CYP26 enzyme inhibitor resulted in an increased number of germ cells with both beta-galactosidase activity and STRA8 protein and an increase in the expression of genes associated with differentiation and reduced expression of a gene associated with undifferentiated germ cells. These results show the action of RA in a subset of spermatogonia leads to nonuniform initiation of differentiation throughout the neonatal testis, potentially mediated through the action of CYP26 enzymes. Thus, the presence of RA is a likely driving factor in the initiation of spermatogonial differentiation and may result in asynchronous spermatogenesis.
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PMID:Retinoic acid availability drives the asynchronous initiation of spermatogonial differentiation in the mouse. 2084 80

Beta-galactosidase activity reflects the rate of cellular aging in vitro. Such activity was quantified at pH 6 in ovarian epithelial cells from 28 donors without a history of cancer, by the chemoluminiscent method. The cells were serially cultured until they achieved the state of permanent growth arrest. During the exponential growth phase, all cultures showed a similar pattern of growth and low beta-galactosidase activity. However, both in the onset of decrease replicative activity, as well as in the onset of the stationary phase, there was a significant rise in the enzyme activity. Our results showed that beta-galactosidase activity can be considered as a replicative senescence marker of the ovarian surface epithelium at pH 6.
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PMID:[Beta-galactosidase activity as a marker of senescence in primary cultures of the ovarian surface epithelium]. 2130 72

Beta-galactosidase, encoded by the lacZ gene in E. coli, can cleave lactose and structurally related compounds to galactose and glucose or structurally related products. Its activity can be measured using an artificial substrate, o-nitrophenyl-beta-D-galactopyranoside (ONPG). Miller firstly described the standard quantitative assay of beta-galactosidase activity in the cells of bacterial cultures by disrupting the cell membrane with the permeabilization solution instead of preparing cell extracts. Therefore, beta-galactosidase became one of the most widely used reporters of gene expression in molecular biology to reflect intracellular gene expression difference. But the Miller assay procedure could not monitor the beta-galactosidase reaction in real time and its results were greatly influenced by some operations in the Miller procedure, such as permeabilization time, reaction time and concentration of the cell suspension. A scanning method based on the Miller method to determine the intracellular beta-galactosidase activity in E. coli Tuner (DE3) expressing -galactosidase in real time was developed and the permeabilization time of cells was optimized for that. The comparison of 3 assays of beta-galactosidase activity (Miller, colorimetric and scanning) was made. The results proved that scanning method for the determination of enzyme activity with using ONPG as substrate is simple, fast and reproducible.
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PMID:Scanning assay of beta-galactosidase activity. 2333 Mar 95

The transgalactosilating ability of beta-galactosidase preparations obtained from Kluyveromyces fragilis, Penicillium canescens, and Escherichia coli was investigated. In samples of hydrolysates of 20% lactose solutions without or with a 2% addition of glucose, the galactose or fructose obtained with the use of the investigated preparations and the content of saccharides was determined with the HPLC method. Under experimental conditions, the highest quantity (56.0-64.1%) of galactooligosaccharides was synthesised by beta-galactosidase obtained from E. coli, while the lowest number (11.25-25.2%) was obtained by beta-galactosidase obtained from P. canescens. Beta-galactosidase from E. coli also synthesised considerable amounts of lactulose.
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PMID:A comparative study on galactoologosaccharide synthesis by selected beta-galactosidase preparations. 2475 91

Endothelial progenitor cells (EPCs) represent a heterogeneous cell population that is believed to be involved in vasculogenesis after ischemic diseases. EPCs could have a potential for future therapies with the purpose of enhancing endothelial repair. However, due to the low amount of these cells in circulation they have to be expanded in vitro before administration into recipients. The purpose of this study was to analyse and evaluate possible changes in morphology and functionality as a result of in vitro ageing of a subtype of EPCs called endothelial outgrowth cells (EOCs), since such changes might compromise the cells' ability to participate in vasculogenesis. EOCs were isolated and grown from human umbilical cord blood using two methodologies with varying degree of cell purification. The changes between the two culture setups and the changes occurring in EOCs over time were traced by flow cytometry and assays for growth, tube formation, and beta-galactosidase production. The cells showed to be indistinguishable from each other during the first weeks of culture. The cells showed a changed morphology with bigger and more granular cells and the growth rate decreased with time. The cells also showed an increased Beta-galactosidase expression and decreased tube formation ability in late passage EOCs. Our data indicates that EOCs undergo senescence during long-term expansion and therefore time for cell harvest has to be validated in order to achieve functional cells still maintaining a therapeutic potential. A possible application in large animal or humans could be local injection of EOCs into affected areas and thereby reducing the need for long-term expansion of the cells.
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PMID:Are endothelial outgrowth cells a potential source for future re-vascularization therapy? 2508 25


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