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)

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

The nifHDKY operon of Klebsiella pneumoniae encodes for structural polypeptides of nitrogenase and requires the nifA gene product for transcription. Mutations that allow transcription of the nifHDKY operon in absence of the nifA gene product were characterized in plasmids containing the regulatory region of nifHDKY and nifH fused in phase to lacZ. beta-Galactosidase activity served as a measure for nifH expression. Most mutations were located in the nif regulatory region and included insertion sequence 2 (IS2) insertions, a sequence duplication, and a base substitution. In Escherichia coli, beta-galactosidase activity expressed from the mutant plasmids in the absence of nifA was 6-30% of the nifA-activated, parental level. Expression from most mutant plasmids was further increased by nifA. In K. pneumoniae, IS2-containing plasmids expressed low levels of beta-galactosidase and responded poorly, if at all, to activation by nifA, whereas expression from other mutant types was similar to that observed in E. coli. Nucleotide sequence analysis of two mutants indicated that sequences within 41 base pairs upstream to the nifH coding sequence were involved in nif-specific regulation. The results suggest that an inverted repeat element in this region, which could theoretically form a cruciform structure in the DNA, is involved in the transcriptional control of the nifHDKY operon.
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PMID:Promoter mutations that allow nifA-independent expression of the nitrogen fixation nifHDKY operon. 631 May 92

beta-Galactosidase has been purified from rabbit brain by a procedure which gives substantially greater purification and yield than the previously reported method. The enzyme was solubilized in 4% aqueous butanol and purified by a procedure which included affinity chromatography on columns of concanavalin A - Sepharose (ConA-Sepharose) and aminophenylthiogalactoside Sepharose (APT galactoside-Sepharose). The activity was resolved by DEAE-Sepharose chromatography into two fractions; the first did not bind to the column and was eluted in the unbound fraction, while the second bound to the column and could be eluted with a salt gradient. The unbound and bound fractions were purified 7600-fold and 4900-fold, respectively, by the newly developed procedure. Both gave two closely migrating protein bands on polyacrylamide gel electrophoresis and the major contaminating protein was beta-hexosaminidase in each case. The enzyme in the unbound fraction had an isoelectric point (pI) of 6.7 and an apparent molecular weight by gel filtration of 114 000 +/- 10 000. The enzyme that bound to DEAE-Sepharose at pH 8.0 and comprised about 60% of the total acid beta-galactosidase activity of rabbit brain eluted from Sephacryl S-200 as a single peak with apparent molecular weight 140 000 +/- 10 000. The two fractions displayed similar relative specific activities towards the synthetic substrates and ganglioside GM1 and lactosyl ceramide. Neither enzyme hydrolyzed galactosyl ceramide. We have immunological evidence which suggests that the two fractions of beta-galactosidase are also structurally related.
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PMID:Improved purification of beta-galactosidase from rabbit brain: two separable fractions share kinetic and structural properties. 641 4

beta-Galactosidase from T. cornutus was resolved into two activity peaks by gel filtration column chromatography. The pH optima of the two peaks designated P1 and P2, were 5.5 and 3.0, respectively, when p-nitrophenyl-beta-D-galactopyranoside was used as the substrate. The molecular weights of P1 and P2 were 700,000 +/- 70,000 and 78,000 +/- 7800, respectively, when estimated by gel filtration chromatography. The activities of both forms of the enzymes are stimulated by anions such as Cl-, Br- and NO-3. While the activity of P1 was stimulated by low anion concentrations, P2 requires 700 times higher anion concentration for similar enhancement of activity. P1, the high molecular weight form hydrolyzes mainly galactose from small molecular weight beta-galactosides, such as p-nitrophenyl-beta-D-galactopyranoside, 4-methylumbelliferyl-beta-D-galactopyranoside, lactose, lactosylceramide and 3-O-beta-D-galactopyranosyl-D-arabinose, whereas P2, the low molecular weight form cleaves, in addition, all the beta-galactosides tested, including 2-hexadecanoylamino-4-nitrophenyl-beta-D-galactopyranoside, GM1-ganglioside, asialo-GM1-ganglioside, asialo fetuin, alpha 1-acid glycoproteins and the tryptic peptides of the glycoproteins. The optimal conditions for the hydrolysis of the terminal galactose from GM1-ganglioside which does not occur in gastropods, such as T. cornutus, was found to require 40 mM NaCl and 1 mM sodium taurodeoxycholate at pH 3.0 in 50 mM sodium citrate buffer, conditions similar to those by mammalian beta-galactosidase.
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PMID:A beta-galactosidase isoenzyme from Turbo cornutus with substrate specificity toward GM1-ganglioside and glycoproteins. 641 42

beta-Galactosidase was isolated from different organs of the wormwood (Artemisia annua L.). The enzyme activity was found to change during the growth and development of the plant. The maximal activity was revealed in reproductive organs at flowering and fruiting stages. Using ion-exchange chromatography, isoelectric focusing and disc electrophoresis in PAAG, two molecular isoforms of beta-galactosidase were detected. Some physicochemical properties of the enzyme were investigated.
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PMID:[Several properties of beta-galactosidase from Artemisia annua L]. 641 87

beta-Galactosidase was normalized by a serine-thiol protease inhibitor, leupeptin with concentration of 10 micrograms/ml in cultured skin fibroblasts from patients with beta-galactosidase-alpha-neuraminidase deficiency (beta-Gal-/Neu-). The induction of this enzyme was not observed in normal cells. Because the enzymic activity of cathepsin B1 increased significantly both in beta-Gal-/Neu- and normal cells by leupeptin loading, the restoration of beta-galactosidase in beta-Gal-/Neu- cells can not be explained by the theory that leupeptin inhibited intracellular degradation of beta-galactosidase molecules. The effects of leupeptin and sucrose on lysosomal hydrolase induction were compared.
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PMID:Induction of beta-galactosidase in beta-galactosidase-alpha-neuraminidase deficiency: effects of leupeptin and sucrose. 643 25

beta-Galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) purified from Aspergillus oryzae was modified with 2,4,6-trichloro-s-triazine derivatives of polyethylene glycol (activated BPEG) having molecular weights of 600, 1500, 2000, and 4000. Polyethylene glycol derivatives were attached to 6 of the 12 amino groups exposed on the surface of the enzyme. Upon modification, the enzymatic activity for a water-soluble substrate, o-nitrophenyl beta-D-galactopyranoside, was reduced with increasing molecular weight of the activated BPEG. On the contrary, the enzymatic activity for another substrate, 4-methylumbelliferyl beta-D-galactopyranoside, was increased upon modification. The Michaelis constants of native and modified enzymes for these two substrates were virtually the same. The effect of the modification was more marked in the enzymatic hydrolysis of the beta-galactosidic bond of amphipathic substrates. A fluorescent analog of naturally occurring galactocerebroside, 1-O-galactosyl-2-N-(1-dimethylaminonaphthalene-5-sulfonyl)-sphingosine, was hydrolyzed more rapidly by the modified enzyme than by the native one. The enzyme modified with activated BPEG of 1500 Da had the highest activity for this substrate. The beta-galactosidic bond of the terminal galactose of GM1-ganglioside (II3NeuAcGgOse4Cer, galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminosyl)-galactosyl -glucosylceramide) was cleaved by the modified but not by the native enzyme.
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PMID:Alteration of the substrate specificity of Aspergillus oryzae beta-galactosidase by modification with polyethylene glycol. 643 28

The yeast SUC2 gene codes for the secreted enzyme invertase. A series of 16 different-sized gene fusions have been constructed between this yeast gene and the Escherichia coli lacZ gene, which codes for the cytoplasmic enzyme beta-galactosidase. Various amounts of SUC2 NH2-terminal coding sequence have been fused in frame to a constant COOH-terminal coding segment of the lacZ gene, resulting in the synthesis of hybrid invertase-beta-galactosidase proteins in Saccharomyces cerevisiae. The hybrid proteins exhibit beta-galactosidase activity, and they are recognized specifically by antisera directed against either invertase or beta-galactosidase. Expression of beta-galactosidase activity is regulated in a manner similar to that observed for invertase activity expressed from a wild-type SUC2 gene: repressed in high-glucose medium and derepressed in low-glucose medium. Unlike wild-type invertase, however, the invertase-beta-galactosidase hybrid proteins are not secreted. Rather, they appear to remain trapped at a very early stage of secretory protein transit: insertion into the endoplasmic reticulum (ER). The hybrid proteins appear only to have undergone core glycosylation, an ER process, and do not receive the additional glycosyl modifications that take place in the Golgi complex. Even those hybrid proteins containing only a short segment of invertase sequences at the NH2 terminus are glycosylated, suggesting that no extensive folding of the invertase polypeptide is required before initiation of transmembrane transfer. beta-Galactosidase activity expressed by the SUC2-lacZ gene fusions cofractionates on Percoll density gradients with ER marker enzymes and not with other organelles. In addition, the hybrid proteins are not accessible to cell-surface labeling by 125I. Accumulation of the invertase-beta-galactosidase hybrid proteins within the ER does not appear to confer a growth-defective phenotype to yeast cells. In this location, however, the hybrid proteins and the beta-galactosidase activity they exhibit could provide a useful biochemical tag for yeast ER membranes.
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PMID:Invertase beta-galactosidase hybrid proteins fail to be transported from the endoplasmic reticulum in Saccharomyces cerevisiae. 644 5

Expression of gnd of Escherichia coli, which encodes the hexose monophosphate shunt enzyme, 6-phosphogluconate dehydrogenase (6PGD; EC 1.1.1.44), is subject to growth rate-dependent regulation: the level of the enzyme is directly proportional to growth rate under a variety of growth conditions. Previous results obtained with strains carrying transcriptional fusions of gnd to the structural genes of the lactose operon suggested that the growth rate-dependent regulation of gnd expression is at the post-transcriptional level. To characterize the regulation further, we prepared with phage MudII a set of eight independent gnd-lac gene (protein) fusions. We showed through genetic analysis and DNA sequencing that each fusion joint was located within the 6PGD-coding sequence between the first and second base pair of a codon, the reading frame required for production of a hybrid 6PGD-beta-galactosidase. Strains harboring the gnd-lac fusion plasmids produced proteins whose mobility in a NaDodSO4/polyacrylamide gel agreed with the molecular weights predicted from the DNA sequence for the respective hybrid proteins. The level of beta-galactosidase was high and relatively growth rate-independent in the fusion whose fusion joint was at codon 48. The level of beta-galactosidase in the other seven fusion strains whose fusion joints were located further downstream in the 6PGD-coding sequence showed the same dependence on growth rate as 6PGD in a normal strain. beta-Galactosidase levels were not affected by the presence of a gnd+ gene in trans to any of the fusions. The results suggest that all sites necessary for growth rate-dependent regulation of 6PGD level lie in gnd upstream from codon 118 and that an essential site of negative control lies within the coding sequence, between codons 48 and 118.
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PMID:Essential site for growth rate-dependent regulation within the Escherichia coli gnd structural gene. 644 Jan 41

The available cytochemical methods for localization of beta-galactosidase have been evaluated using pollen grains of Brassica campestris. beta-Galactosidase-deficient pollen (gal), served as a control. Azo dye methods involving naphthyl substrates showed high and nonspecific background staining to the exine. The indigogenic method, employing 5-bromo-4-chloro-3-indoxyl beta-D-galactoside (X-gal) as the enzyme substrate, gave specific opaque-blue final reaction product, while mutant pollen grains remained colourless. Final reaction product formation was blocked by D-galactono-1,4-lactone, thus demonstrating the specificity of the enzyme reaction. Using microspectrophotometry, the absorbance of the final reaction product was found to be a linear function of incubation time and section thickness in cryostat sections up to 8 micron thick and was only slightly reduced by glutaraldehyde prefixation. The validity of the indigogenic method for quantitative analysis was confirmed by using an enzyme-containing polyacrylamide gel model system and enzyme-coupled Sepharose 4B beads. Cellular sites of enzymic activity have been determined using plastic sections: final reaction product occurred in the intine wall layer and peripheral cytoplasm.
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PMID:Quantitative cytochemistry of beta-galactosidase in normal and enzyme deficient (gal) pollen of Brassica campestris: application of the indigogenic method. 644 87


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