Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The specificity of lactoperoxidase-catalyzed iodination for the proteins of the hepatoma tissue culture cell plasma membrane was examined by histochemical, biochemical, and cell fractionation techniques. Light microscope autoradiography of sectioned cells shows the incorporated label to be localized primarily at the periphery of the cell. Most of this label can be released from the cell by trypsin but not by collagenase or hyaluronidase. The label is recovered from the cells as either monoiodotyrosine or diiodotyrosine after hydrolysis of cell extracts with a mixture of proteolytic enzymes. The label co-purifies during cell fractionation with an authentic liver cell plasma membrane marker enzyme, 5'-nucleotidase. Thus, the incorporated iodide is itself a valid marker for those membrane polypeptides having tyrosine residues accessible to the lactoperoxidase. The polypeptide complexity of the purified plasma membrane was examined by high resolution dodecyl sulfate-polyacrylamide gel electrophoresis. At least 50 polypeptides in the membrane are accessible to iodination. These polypeptides probably represent the bulk of the protein mass of the membrane and iodinating them does not affect cell viability, growth rate, or cell function. Labeling experiments with fucose and glucosamine show that at least nine of the iodinated peptides may be glycoproteins.
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PMID:Proteins of the hepatoma tissue culture cell plasma membrane. 0 57

Two strains of Escherichia coli and one strain each of Salmonella typhimurium and Pseudomonas aeruginosa were killed by the bactericidal activity of the lactoperoxidase-thiocyanate-hydrogen peroxide system in milk and in a synthetic medium. H2O2 was supplied exogenously by glucose oxidase, and glucose was produced at a level which was itself noninhibitory. Two phases were distinguished: the first phase was dependent on the oxidation of SCN(-) by lactoperoxidase and H2O2, which was reversed by reducing agent, and the second phase was dependent on the presence of accumulated H2O2, which was reversed by catalase. The latter enzyme could also reverse the first phase, but only when present in excessive and unphysiological levels. The bactericidal activity was greatest at pH 5 and below, and it depended on the SCN(-)concentration and on the number of organisms. Since raw or heated milk neutralizes the acid barrier against infection in the stomach, the bactericidal system discussed may contribute to the prevention of enteric infections in neonates.
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PMID:Nonspecific bactericidal activity of the lactoperoxidases-thiocyanate-hydrogen peroxide system of milk against Escherichia coli and some gram-negative pathogens. 0 74

To produce a 125I-labelled glucagon suitable for radioligand assays, we studied the influence of variations in the lactoperoxidase iodination method. Both the degree of iodine substitution and the formation of monoiodo- or diiodo-tyrosines were pH dependent. The substitution increased and the diiodo-/monoiodotyrosine ratio decreased when pH increased. These two factors affected the immunoreactivity of the iodoglucagon relatively independently of each other. It was found that iodination at pH 10.0 with an average of 0.3 gatom I/mol glucagon resulted in 125I-labelled glucagon with higher immunoreactivity and stability than that produced at the conventional pH 7.5 and 8.5.
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PMID:Improved radioiodination of glucagon with the lactoperoxidase method. Influence of pH on iodine substitution. 0 74

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

18 subjects, 9 males and 9 females, were examined regarding salivary oxidation-reduction potential, salivary flow rate, salivary peroxidase activity, oxidation-reduction potential of dental plaque samples, and dental health. Both the peroxidase activity, expressed as the salivary lactoperoxidase, and the salivary oxidation-reduction potential increased with increasing salivary flow rate. The variation of these variables was obviously due to changes in salivary flow rate during the day. The remarkably slight differences in peroxidase activities, oxidation-reduction potentials and salivary flow rate in this study did not have any marked correlation with the clinical recordings of the test groups.
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PMID:The correlation between salivary peroxidase activity, salivary flow rate, and the oxidation-reduction potentials of human saliva and dental plaque suspensions. 0 73

Cyanide has been shown to stimulate both oxygen uptake and hexose monophosphate shunt activity in phagocytizing human polymorphonuclear leukocytes. It also stimulates the oxidation of NADPH by a particulate fraction derived from phagocytizing cells. This stimulation of NADPH oxidase is not observed in the presence of exogenous Mn2+. Studies with purified enzymes have shown that CN- also stimulates NADPH oxidation by horseradish peroxidase or lactoperoxidase, suggesting that the respiratory burst might be initiated by activation of a peroxidase-like enzyme in the human polymorphonuclear leukocyte. Based on studies of others, however, it does not appear as though the enzyme is identical to myeloperoxidase. The mechanism of the CN- stimulation appears to involve an oxidatic chain reaction, since it stimulates markedly NADPH oxidation in the presence of an artificial superoxide-generating system.
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PMID:Effect of cyanide on NADPH oxidation by granules from human polymorphonuclear leukocytes. 1 79

Synthetic porcine secretion was labelled by the conjugation-labelling method of Bolton & Hunter, the lactoperoxidase method, the gaseous diffusion method, and the chloramine-T method. The chloramine-T technique was adapted as routine method. Ten mug (3.27 nmol) peptide was reacted with 5 mCi of Na125I at a concentration of chloramine-T of 1.3 mmol/l. Synthetic secretin was suitable for labelling for at least eight months when stored as dry matter in nitrogen-filled glass ampoules. Purification and separation of labelled from unlabelled hormone was carried out by gel-permeation chromatography on Sephadex G-50 superfine. The labelled preparation had a specific radioactivity of 405 +/- 33 muCi/nmol (mean +/- SEM., n = 9) and was unable for six days. 6-tyrosyl-secretin took more iodine compared to porcine synthetic secretin but had lower immunoreactivity with all antisera tested.
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PMID:Preparation of 125I-labeled synthetic porcine secretin for radioimmunoassay. 1 92

This report describes the conditions that are necessary for iodination of staphylococcal enterotoxin B (SEB) by use of chloramine-T. Makor Chemical Co. SEB and the two major SEB components, which were prepared by isoelectric focusing of partially purified SEB, were used in these studies. The antigenic activity of the SEB preparations was monitored by radioimmunoassay as the oxidation/reduction (O/R) potential was increased by addition of chloramine-T. The SEB preparations lost antigenic activity rapidly at pH 7.5 and room temperature when sufficient chloramine-T was added to raise the O/R potential above 250 mV. Iodinated SEB with satisfactory immunoreactivity was prepared by omitting carrier iodide from the iodination reaction mixture and by using at least 1 mg of SEB/ml, steps which made the O/R potential more stable, and by stopping the reaction before the O/R potential exceeded 250 mV. Comparison of the chloramine-T method with a lactoperoxidase/H2O2 method of iodinating SEB showed the latter to cause a greater loss of immunoreactivity.
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PMID:Iodination of staphylococcal enterotoxin B by use of chloramine-T. 1 66

Studies were carried out to identify transmembrane bridging proteins in the plasma membrane of mouse L-929 cells. Cells grown in suspension culture were 125I-labeled by lactoperoxidase and allowed to ingest latex particles to produce inside-out membrane phagosome preparations. Phagosomes were isolated and the inner membrane surface was labeled with N-(5'-aminopentyl)-5-dimethylamino-1-naphthalenesulfonamide (dansylcadavarine) by a transglutaminase-catalyzed reaction. The phagosome membrane proteins were solubilized and dansylcadavarine-labeled proteins were isolated by anti-dansyl immunoadsorbent affinity chromatography. Dansylcadavarine-labeled proteins were analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and autoradiography for the presence of 125I-labeled material. By this technique, two iodinated proteins with molecular weights of approximately 50,000 and 80,000 appear to be selectively retained by the anti-dansyl immunoadsorbent, suggesting that these proteins span the plasma membrane.
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PMID:Identification of transmembrane bridging proteins in the plasma membrane of cultured mouse L cells. 2 34

In squid axon, internal alkalinization from pH 7.1 to pH 10.2 results in a reversible decrease of the maximum inward current and the steady state sodium channel inactivation. Similar effects were observed after treatment of the axon with tetranitromethane or after iodination with lactoperoxidase. These results suggest that a tyrosine residue is an essential component of the inactivation process in this nerve.
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PMID:Sodium channel inactivation in squid axon is removed by high internal pH or tyrosine-specific reagents. 2 73


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