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PubMed1987

Diplococcal beta-galactosidase with a specificity reacting to beta 1-4 linkage but not to beta 1-3 linkage as a useful exoglycosidase for the structural elucidation of glycolipids.

Diplococcal beta-galactosidase, which is known to be useful for the structural studies of glycoprotein-linked oligosaccharides, was found to show the same substrate specificity in cleaving Gal beta 1-4 linkages of glycolipids as that of the oligosaccharides. The optimum conditions of beta-galactosidase in the 80% ammonium sulfate precipitates of the culture medium of Streptococcus (Diplococcus) pneumoniae were determined with nLcOse4Cer radiolabeled by the galactose oxidase-NaB3H4 procedure. Detergent was required for the highest activity, and different combinations of several buffers and detergents showed different properties in stimulating beta-galactosidase, and in enhancing or suppressing N-acetyl-beta-hexosaminidase which was contaminated in the enzyme preparation. The optimum pH was found to be at 6.5, and specific activity and Km were 8.1 nmol/mg protein/h and 1 nmol, respectively. While more than 70% of beta-galactose was liberated from LacCer and nLcOse4Cer within 1 h under the optimum conditions to form GlcCer and nLcOse3Cer, respectively, none was liberated from LcOse4Cer, GalCer, GgOse4Cer, GbOse3Cer, IV3 alpha GalnLcOse4Cer, and Il3NeuAcGgOse4Cer, showing the substrate specificity solely to Gal beta 1-4 linkage.

Carbohydrate Conformation↗

PubMed1983

Biosynthesis of alpha-galactosidase A in cultured Chang liver cells.

An investigation of the structure and biosynthesis of alpha-galactosidase A (alpha-D-galactoside glycohydrolase, EC 3.2.1.22) and its N-linked oligosaccharide chains was undertaken by metabolic labeling of Chang liver cells with [2-3H]mannose, immunoprecipitation of the activity, and examination of the resulting immunoprecipitates. From cells pulse labeled for 3 h, two radioactive bands with Mr = 58,000 and 49,000 were detected by SDS-gel electrophoresis; following a 20-h chase, only the Mr = 49,000 band was observed. Examination of the oligosaccharide fraction derived from pulse-labeled enzyme revealed that 18% of the asparagine-linked oligosaccharides were complex and 82% were high-mannose type. After a 20-h chase, 48% of the oligosaccharides were complex and 52% were high mannose. The high-mannose oligosaccharides of alpha-galactosidase A immunoprecipitated from both pulsed and pulse-chased cells had the same mobilities as Man8-9GlcNAc on thin-layer chromatography and Bio-Gel P-4. Two fractions of complex glycopeptides derived from the alpha-galactosidase A of pulsed and pulse-chased cells had the same migration on Bio-Gel P-4 as glucose oligomers containing 14 and 19-39 glucose units. Based on their apparent size and their behavior on concanavalin A-Sepharose, the complex oligosaccharides are believed to be composed of tri- and/or tetraantennary structures.

Animals↗

PubMed1986

Reversion reactions of beta-galactosidase (Escherichia coli).

The reversion reactions of beta-galactosidase (Escherichia coli) produced beta-galactosyl-galactoses and beta-galactosyl-glucoses. About 10 beta-galactosyl-galactose and 10 beta-galactosyl-glucose gas-liquid chromatographic peaks were detected and it is thus very likely that every possible isomer of beta-galactosyl-galactose and beta-galactosyl-glucose was formed by the reversion reactions (taking into account both anomers for each isomer). The presence of lactose and allolactose among the beta-galactosyl-glucoses was confirmed with standards. An important finding relating to the role of allolactose as an inducer of the lac operon was that allolactose (beta-D-galactosyl-(1----6)-D-glucose) was the only disaccharide formed initially, and at equilibrium it was present in the largest amount (50%). Obviously the enzyme is specific in its ability to form allolactose, and allolactose is the most stable beta-galactosyl-glucose, both important inducer properties. The equilibrium constant (concentration of disaccharides divided by the concentration of reactants at equilibrium) of the reaction was about 9.5 mM-1. This is the first report of an equilibrium constant for the beta-galactosidase reaction. Of mechanistic significance is the fact that only three compounds were able to replace D-galactose as a reversion reactant. Two of these (L-arabinose and D-fucose) had alterations at carbon 6. The 6 position, therefore, is not essential for reactivity. The third compound was D-galactal. Any other sugars tested (even with very minor changes relative to D-galactose) did not react. Of special consequence is the 2 position. The results strongly suggest that there has to be either an equatorial hydroxyl at the 2 position of a sugar or a special reactivity (as with D-galactal) in order for the enzyme to catalyze the beta-galactosidase reaction.

Binding Sites↗

PubMed1978

Purification of jack bean meal beta-D-galactosidase by a new affinity adsorbent.

A simple procedure has been developed for the purification of jack bean beta-D-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) by affinity chromatography employing a new affinity adsorbent. The ligand 6-N-beta-(4-aminophenyl)-ethylamino-3-O-beta-D-galactopyranosyl-6-deoxy-L-gulitol was prepared by the reaction between lactose and beta-(4-aminophenyl)-ethylamine and was coupled to cyanogen bromide activated Sepharose 4B via the amino groups of the 4-aminophenyl moiety. This affinity gel resulted in a 111-fold purification of beta-D-galactosidase with a 64% recovery of the enzyme. With p-nitrophenyl-beta-D-galactopyranoside as the substrate the apparent Km and V values were 0.59 mM and 1.87 mumol/min per mg, respectively. The method for purification of beta-D-galactosidase may be applicable to other glycosidases depending upon the choice of specific di- or oligosaccharides of known structures to be used in the preparation of ligands.

Chromatography, Affinity↗

PubMed1987

The fate of internalized alpha-2-macroglobulin: alpha-galactosidase conjugate in fibroblasts from Fabry's hemizygote.

In our previous report we described the endocytotic incorporation of coffee bean alpha-galactosidase conjugated to human alpha-2-macroglobulin (alpha-2-M) into cultured fibroblasts derived from a patient with Fabry's disease (1). The fate of internalized alpha-galactosidase according to the method described in the above report is now studied. Measurement of the enzyme activity of subcellular fractions showed that it was concentrated in the lysosomal-mitochondrial fraction. The half-life of internalized alpha-galactosidase was determined to be 2 h.

Cells, Cultured↗

PubMed1990

Expression, glycosylation, and intracellular distribution of human beta-galactosidase in recombinant baculovirus-infected Spodoptera frugiperda cells.

A full-length cDNA encoding human acid beta-galactosidase was inserted into the baculovirus genome under transcriptional regulation of the viral polyhedrin gene promoter. The Spodoptera frugiperda cells infected with the recombinant virus expressed the beta-galactosidase activity 300-fold higher than human fibroblasts. Immunoblot analysis revealed an 82-kDa protein band, which was modified in molecular size by deglycosylating enzymes; an 80-kDa band appeared after N-glycanase digestion, and two bands (80-kDa and 81-kDa) appeared after endoglycosidase H digestion. This result suggested that the enzyme molecule was glycosylated, partly with high-mannose type oligosaccharides. The intracellular distribution of the enzyme observed by indirect immunofluorescence staining was perinuclear or diffusely cytoplasmic, and not characteristic of lysosomes; the enzyme was secreted to the culture medium in large quantities, and not translocated to lysosomes. Possible application of this expression system to the studies of the structure and function of normal and mutant human beta-galactosidases was discussed.

Animals↗

PubMed1983

Effects of thiol protease inhibitors on intracellular degradation of exogenous beta-galactosidase in cultured human skin fibroblasts.

The effects of low molecular weight (LMW) protease inhibitors of microbial origin were evaluated on the intracellular degradation of beta-galactosidase purified from Aspergillus oryzae and taken up by cultured human skin fibroblasts with beta-galactosidase deficiency. Only thiol protease inhibitors showed an effect to increase the enzyme activity. E-64, a specific inhibitor of thiol proteases, prolonged 3-fold a half life of the exogenous beta-galactosidase and when the enzyme was supplied as liposomes, the half life was prolonged 9-fold in these cells. The role of thiol proteases in the degradation of enzyme molecules was discussed.

Biological Transport↗

PubMed1986

Expression of the human apolipoprotein AI gene fused to the E. coli gene for beta-galactosidase.

The human apoAI gene was expressed in E. coli by in-frame fusion to a modified beta-galactosidase gene present in plasmid pUR291. The fused beta-galactosidase-apoAI gene product was expressed at a high level and was recognized by an anti-human apoAI antiserum. Besides the fused protein, at least one degradation product having an Mr similar to that of beta-galactosidase was present in high amounts in bacterial extracts. These results and those of a pulse-chase experiment indicate that degradation took place only in the apoAI moiety of the chimeric protein.

Apolipoprotein A-I↗

PubMed1984

Effect of dextran and modified dextrans on the uptake and degradation of beta-galactosidase in isolated liver cells.

Conjugation of beta-galactosidase with either dextran, methylated dextran or acetylated dextran had only a small effect on uptake of the enzyme in isolated rat parenchymal and nonparenchymal liver cells. Conjugation of beta-galactosidase with dextran or the modified dextrans, reduced the intracellular degradation of the enzyme by up to about 45%. Methylated dextran had less effect than unmodified dextran or acetylated dextran on reducing the intracellular degradation of beta-galactosidase.

Animals↗

PubMed1987

Copurification and separation of beta-galactosidase and sialidase from porcine testis.

A soluble sialidase was copurified apparently as an enzyme complex with acid beta-galactosidase from porcine testis. The sialidase exhibited its maximum activity at acidic pH. It was efficiently active towards 4-methylumbelliferyl-alpha-D-N-acetyl-neuraminic acid and sialyllactose, relatively inactive towards glycoproteins, and had little activity towards glycolipids. The complex could be separated by sucrose gradient centrifugation or isoelectric focusing. The separated enzymes had molecular weights about 600,000 for beta-galactosidase and more than about 1,000,000 for sialidase by Sepharose 4B gel filtration. SDS-polyacrylamide gel electrophoresis of the beta-galactosidase showed three protein bands with molecular weights of 63,000, 31,000 and 20,000.

Animals↗

PubMed1987

Heterogeneity of acid beta-galactosidase from rabbit kidney.

1. Rabbit kidney acid beta-galactosidase can be resolved into three peaks (named A3, A2 and A1) by gel-filtration chromatography. Their estimated molecular weights were: more than 250,000, 150,000 and 17,000 respectively. 2. The purified acid form appeared as a single band of protein (Mr = 28,000) on electrophoresis in the presence of sodium dodecyl sulphate, suggesting that forms A3 and A2 are multimeric forms of beta-galactosidase A1. 3. Treatment with neuraminidase from Clostridium perfringens converts form A3 into a more basic form. This phenomenon occurs also when this form is stored for a week at 4 degrees C and parallels its disaggregation. 4. The data suggest that the sialic acids present in the multimeric forms are involved in the aggregation of the acidic form of beta-galactosidase.

Animals↗

PubMed1979

A comparison of the ability of beta-galactosidase and horseradish peroxidase enzyme-antibody conjugates to detect specific antibodies.

The ability of two different enzyme-antibody conjugates to detect specific antibodies has been compared. beta-Galactosidase was conjugated to antibodies raised against rabbit Fc fragments using m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS). Horseradish peroxidase (HRP) was conjugated to part of the same batch of antibodies using the periodate method. The beta-galactosidase and HRP labels enabled detection of approximately 8 fmoles and 4 fmoles respectively of human growth hormone (HGH) antibodies, when their enzyme activities were measured spectrophotometrically. The detection limit of the beta-galactosidase label was increased 4-fold when a fluorimetric detection system was employed.

Animals↗

PubMed1988

Erythropoietin-beta-D-galactosidase. The generation, purification and use of a fusion protein.

A human erythropoietin (Epo) cDNA fragment encoding the complete erythropoietin peptide sequence was fused to the 3'-end of the lacZ gene in the polylinker region of the high expression vector, pUR 278. Escherichia coli bacteria were transformed with the recombinant plasmid harboring the hybrid Epo-beta-D-galactosidase gene. After induction with isopropyl-thiogalactoside large amounts of the fusion protein, Epo-beta-D-galactosidase were synthesized in the transformed bacteria. The fusion protein was partially purified and shown to exhibit intact galactosidase enzymatic activity. Although no biological activity of the Epo counterpart of the fusion protein was detected both in an in vivo and in an in vitro bioassay, the fusion protein served as an effective antigen for the production of anti-erythropoietin antibodies. Antifusion protein antibodies raised in rabbits were shown to react with the intact human Epo molecule from erythropoietin producing culture supernatants. The affinity of these anti-fusion protein antibodies was sufficiently high to permit the development of a sensitive radioimmunoassay for human Epo. This fusion protein approach is a relatively straightforward and rapid method of generating antibodies with specificity for any protein encoded by a cloned eukaryotic gene.

Animals↗

PubMed1984

Targeting of E. coli beta-galactosidase to the nucleus in yeast.

In order to identify determinants governing nuclear protein localization, we constructed a set of hybrid genes by fusing the S. cerevisiae gene, MAT alpha 2, coding for a presumptive nuclear protein, and the E. coli gene, lacZ, coding for beta-galactosidase. The resultant hybrid proteins contain 3, 13, 25, 67, or all 210 amino acids of wild-type alpha 2 protein at the amino terminus and a constant, enzymatically active portion of beta-galactosidase at the carboxy terminus. Indirect immunofluorescence and subcellular fractionation studies with yeast cells containing the alpha 2-LacZ hybrid proteins indicate that the alpha 2 segment can direct localization of beta-galactosidase to the nucleus. A segment as small as 13 amino acids from alpha 2 is sufficient for this localization. Comparison of amino acid sequences of other nuclear proteins with this region of alpha 2 reveals a sequence that may be necessary for nuclear targeting. Production of some alpha 2-LacZ hybrid proteins causes cell death, perhaps as a result of improper or incomplete localization. These studies also indicate that the alpha 2 protein, argued on genetic grounds to be a negative regulator, acts in the yeast nucleus.

Base Sequence↗

PubMed1988

Genetic engineering of methionyl-tRNA synthetase: in vitro regeneration of an active synthetase by proteolytic cleavage of a methionyl-tRNA synthetase--beta-galactosidase chimeric protein.

The construction of a family of plasmids carrying derivatives of metG, the gene for E. coli methionyl-tRNA synthetase, is described. These plasmids allow expression of native or truncated forms of the enzyme and easy purification of the products. To facilitate the characterization of modified enzymes with very low catalytic activity, a specialized vector was constructed, in which metG was fused in frame with lacZ, the gene for beta-galactosidase. This plasmid expresses a methionyl-tRNA synthetase-beta-galactosidase chimeric protein, which is shown to carry the activities of both enzymes. This hybrid can be purified in a single step of affinity chromatography for beta-galactosidase. The methionyl-tRNA synthetase moiety can be regenerated by mild proteolysis, thus providing a simple method for purifying and studying mutated proteins.

Amino Acyl-tRNA Synthetases↗

PubMed1988

Purification and characterization of human liver beta-galactosidase from a patient with the adult form of GM1 gangliosidosis and a normal control.

beta-Galactosidases were purified to homogeneity from livers of a normal control and a patient with the adult form of GM1 gangliosidosis. The purification was achieved by chromatography on DEAE-Sepharose fast flow, Con A-Sepharose, p-aminophenyl-1-thio-beta-D-galactopyranoside-Sepharose, and QAE-Mono Q. The normal and mutant enzymes were purified about 5000-fold with a yield of 10% and 1800-fold with a yield of 34%, respectively, and could hydrolyze 4-methylumbelliferyl-beta-D-galactoside, GM1 ganglioside, and asialofetuin. The purified normal enzyme was eluted from a TSK gel G-4000SW column as three symmetrical peaks of protein which were coincident with the three peaks of enzyme activity. The enzyme in these three peaks had apparent molecular weights of 800,000 (polymer), 140,000 (dimer), and 65,000 (monomer), whereas the mutant enzyme was eluted as two symmetrical peaks of protein and enzyme activity. The apparent molecular weight of a major monomeric form of the enzyme (beta-galactosidase A) was 60,000, and no dimeric form of the enzyme existed. Normal and mutant purified enzyme preparations migrated as a single major protein band with apparent molecular weights of 65,000 or 60,000, respectively, by SDS-polyacrylamide gel electrophoresis after treatment with mercaptoethanol. On isoelectric focussing, the mutant enzyme migrated more anodally than the normal enzyme. The mutant enzyme also had altered enzyme properties, such as pH optimum, Km values, substrate specificity and heat-stability. These data on the characteristics of the purified enzyme preparations provide the first direct evidence that patients with the adult form of GM1 gangliosidosis have a structurally altered beta-galactosidase.

Adult↗

PubMed1978

Difference in renal alpha-galactosidase levels in male and female Chinese hamsters (Cricetulus griseus).

1. The activity of alpha-galactosidase was found to be significantly higher in the kidney of female than that of male Chinese hamsters in a highly inbred colony but its activity in liver, heart and spleen remained similar between female and male animals. 2. Partially purified renal alpha-galactosidase by sequential column chromatography on Sepharose 6B and DEAE-Sepharose CL-6B showed identical elution profiles, pH optima (4.5), KmS (4.4 mM) and heat-inactivation curves between enzymes of male and female animals. 3. Thus, the observed higher activity of renal alpha-galactosidase in the females was due to elevated enzyme concentration, not a result of enzyme polymorphism.

Animals↗

PubMed1987

Absence of beta-galactosidase (lactase) activity from intestinal brush borders of suckling macropods: implications for mechanism of lactose absorption.

1. Neutral beta-galactosidase (lactase) activity was absent from crude brush borders of small intestines of three species of suckling macropods (kangaroos and wallabies), even though the intestinal mucosal homogenates had high beta-galactosidase activities. 2. These activities were entirely due to an intracellular acid beta-galactosidase, probably located in lysosomes. 3. The results suggest that the absorptive-digestive mechanism for lactose in macropods is fundamentally different from that in eutherian mammals.

Animals↗