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)

A method using p-benzoquinone for coupling antigens and antibodies to enzymes and erythrocytes is described. The method involves the treatment of proteins (or polysaccharides) at pH 6 or 7 with an excess of p-benzoquinone. After removal of the unreacted reagent by gel filtration, the "activated" proteins were coupled at pH 8-9 with enzymes or erythrocytes. Biological activities of the proteins were not substantially modified by this treatment since 80-100% of the antigen binding capacity was found to be preserved in p-benzoquinone treated antibodies or Fab fragments. Anti-Ig antibodies (or Fab) were coupled by this procedure to peroxidase, alkaline phosphatase, lactoperoxidase, glucose oxidase and beta-galactosidase, and the conjugates obtained were found to be highly effective in detecting intracellular Ig by immunohistochemical techniques. Erythrocytes coated with sheep anti-mouse Ig antibody or Fab were used to titrate by passive hemagglutination serum Ig. The same erythrocytes were employed to detect by plaque assay mouse Ig secreting cells. Erythrocytes coated with peroxidase, alkaline phosphatase, bovine serum albumin, ribonuclease, Salmonella polysaccharide (B 27 +) and pneumoccocal polysaccharide SIII were employed to titrate serum antibody by passive hemagglutination and hemolysis and to detect mouse antibody secreting cells by plaque assay. All the antigens and antibodies coated erythrocytes prepared gave highly satisfactory and reproducible results.
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PMID:A new method using p-benzoquinone for coupling antigens and antibodies to marker substances. 0 79

Lactoperoxidase catalyzes the oxidation of thiocyanate by hydrogen peroxide and an intermediary product is formed with antibacterial properties. The components of this system, with the exception of hydrogen peroxide, are present in milk. H2O2 may be introduced by means of enzymatic generation and thus make the system complete. A two-enzyme system consisting of beta-galactosidase and glucose oxidase has been developed for this purpose. The coupled enzyme reaction is shown to work with high efficiency at the neutral pH of milk although the enzymes as such, particularly lactases suitable for immobilization, have optimal activities at much lower pH values. The results indicate that the lactoperoxidase system may in this way be employed to inactivate bacteria present in milk.
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PMID:An immobilized two-enzyme system for the activation of the lactoperoxidase antibacterial system in milk. 98 68

Expression of apical cell surface proteins and glycoproteins was examined in polarized primary cultures of mouse uterine epithelial cells (UEC). Lectin-gold cytochemistry revealed that wheat germ agglutinin (WGA) bound specifically to the components of the apical glycocalyx as well as intracellular vesicles. Double labeling with the pH sensitive dye 3-(2,4-dinitroanilino)-3'amino-N-methyldipropylamine (DAMP) demonstrated the acidic nature of the WGA-staining intracellular vesicles. The enzymatic and chemical sensitivities of the WGA binding sites on the apical cell surface were monitored both by WGA-gold staining as well as by 125I-WGA binding assays. In thin sections, a large fraction of these sites were removed by pronase; however, application of a wide variety of proteases, glycosidases, or chemical treatments to the apical surface of intact UEC failed to reduce WGA binding. In no case did treatments designed to remove sialic acids reduce 125I-WGA binding more than 12%. In contrast, endo-beta-galactosidase as well as a combination of beta-galactosidase with beta-hexosaminidase succeeded in removing 28% and 77% of these sites, respectively. These studies suggested that the majority of the apically disposed WGA binding sites involved N-acetylglucosamine residues rather than sialic acids and included lactosaminoglycans. Many of the proteins detected at the apical cell surface by lactoperoxidase-catalyzed radioiodination were WGA-binding glycoproteins. A major class of these glycoproteins displayed Mr > 200 kDa by SDS-PAGE and was heavily labeled metabolically by 3H-glucosamine or by vectorial labeling at the apical cell surface with galactosyl transferase and UDP-3H-galactose. Analyses of the 3H-labeled oligosaccharides labeled by either procedure indicated that a large fraction of the apically disposed WGA-binding oligosaccharides consisted of neutral, O-linked mucin-type structures with median MW of approximately 1,500. Oligosaccharides in this fraction were partially (15%) sensitive to endo-beta-galactosidase digestion and bound to Datura stramonium agglutinin (68%), demonstrating the presence of lactosaminoglycan sequences. UEC were an extremely effective barrier to attachment or invasion by either a highly invasive melanoma cell line, B16-BL6, or implantation-competent mouse blastocysts. In contrast, neither uterine stromal cells nor a non-polarizing UEC cell line, RL95, prevented B16-BL6 attachment.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:WGA-binding, mucin glycoproteins protect the apical cell surface of mouse uterine epithelial cells. 129 97

The incorporation of 125I, using lactoperoxidase, and the subsequent inactivation of beta-galactosidase in the period when incorporation and inactivation were stoichiometric were investigated in detail. The high pressure liquid chromatographic (HPLC) radioactive profiles of the tryptic peptides of samples taken in the stoichiometric period showed that, although two labelled peptides predominated, there were other labelled peptides. The predominating peptides were shown to be the mono- and di-iodinated forms of the peptide containing Tyr-253. This confirmed the result of an earlier study, but quantitation showed that this iodination accounted for only 15-18% of the total. To show that the other labelled peptides in the HPLC profiles were not merely oxidized or partially digested forms of the peptide containing Tyr-253, two experiments were carried out. In one of the experiments, two of the other labelled peptides were isolated and identified as iodinated forms of the peptide containing Tyr-285 (5-7% of the incorporation). In the other experiment, four additional labelled fractions from the HPLC eluate were treated further with trypsin. No further digestion was observed and thus these peptides did not result from incomplete digestion of the sequence containing Tyr-253. Overall, these results show that, although the incorporation of 125I was stoichiometric with inactivation, no single Tyr was responsible for the inactivation as was tentatively suggested previously. The competitive inhibitor isopropyl-beta-D-thiogalactopyranoside (IPTG) was effective in reducing the rates of inactivation of the enzyme and incorporation of 125I, but the same peptides were labelled in the presence of IPTG as in its absence.
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PMID:A detailed examination of the iodination of beta-galactosidase: stoichiometric inactivation by nonspecific iodination. 309 Oct 51

Beta-Galactosidase is rapidly inactivated by iodination catalyzed by lactoperoxidase but is not inactivated in the presence of the substrate analogue, isopropyl beta-D-thiogalactoside (IPTG). Enzyme activity is lost upon the incorporation of 1 mol of iodine per mol of monomer, without dissociation of the tetrameric structure. Tryptic digests of beta-galactosidase iodinated with 125I in the presence and absence of IPTG were separated by high-performance liquid chromatography and were compared. One fraction was found to be more highly labeled in the digest from the inactivated protein. After isolation of the peptide, amino acid analysis indicated it to be Asp-Tyr-Leu-Arg, residues 252-255. Thus, Tyr-253 is the most reactive tyrosine in beta-galactosidase. This suggests that the conformation of this region of the protein may be altered by binding of IPTG to make Tyr-253 less accessible to iodination. Alternatively, Tyr-253 could be an active-site residue.
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PMID:Inactivation of beta-Galactosidase by iodination of tyrosine-253. 681 83

An Escherichia coli tyrosine auxotroph (MR1) with an inducible lacZ was generated by mutagenesis. Of several tyrosine derivatives tested, only m-fluorotyrosine supported the growth of this mutant and allowed synthesis of active beta-galactosidase. The pH profiles of the beta-galactosidase that was obtained when this mutant was grown on m-fluorotyrosine (81.5% of the tyrosine was replaced by m-fluorotyrosine) indicated that a tyrosine may be acting as a general acid-base catalyst and that it (or another tyrosine with the same pKa) may be involved in substrate binding. Inactivation of normal beta-galactosidase by treatment with lactoperoxidase in the presence of I- did not affect affinity-column binding, but incubation of this iodinated beta-galactosidase with chymotrypsin caused a rapid degradation of a portion of the treated enzyme equal to the portion of the activity that was lost. A study with 125I- showed that the rapid degradation was mainly confined to iodinated molecules of enzyme. These studies indicate that iodination of beta-galactosidase does not affect binding ability, but causes the enzyme to lose catalytic activity and become susceptible to chymotryptic action. Chloroperoxidase also caused rapid inactivation of normal beta-galactosidase in the presence of Br- or I-, but there was a lag followed by a slow inactivation in the presence of Cl-.
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PMID:The properties of beta-galactosidases (Escherichia coli) with halogenated tyrosines. 839 70