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:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that lactoperoxidase (LPO) covalently coupled to polystyrene tissue culture flasks can be used to radioiodinate monolayer cell proteins that come into intimate contact with the LPO-polystyrene surface. These studies have now been extended to include a detailed examination of the class of iodinated polypeptides migrating with apparent molecular weights of 50,000 and 55,000 in SDS polyacrylamide gels. Whereas in cultured L929 cells the 55,000 band is predominantly iodinated, in thioglycollate-activated murine peritoneal macrophages the 55,000 and 50,000 bands are of equal intensity. It is possible that the marked degree of exposure of the 50,000 mol wt polypeptide to immobilized LPO is related to the unique strength of macrophages attachment. After labeling of both L929 cells and macrophages with immobilized LPO, all polypeptides in this molecular weight region were subjected to peptide mapping by simultaneous limited proteolysis and electrophoresis in a second SDS polyacrylamide slab gel. The results clearly show that the two major polypeptides in this region are identical within the limits of resolution of this technique. The 55,000 mol wt polypeptide can also be identified in Triton X-100 cytoskeletons from L929 cells after labeling with soluble LPO either before or after detergent lysis. We conclude that this cell surface polypeptide is in continuity with the cytoskeleton and is preferentially exposed to the substratum during attachment to polystyrene.
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PMID:Identification of cytoskeletal components involved in attachment of L929 cells and macrophages to polystyrene. 719 5

The occurrence of endocytotic mechanisms in human small-intestinal absorptive cells was investigated by culturing biopsy specimens in the presence of horseradish peroxidase (HRP), lactoperoxidase (LPO), and ferritin. The results indicate that both HRP and LPO entered the cells by apical endocytosis, after which they were transported via apical vesicles and tubules to the lysosome-like bodies. Ferritin, which showed a distinct affinity for the cell-coat glycoproteins, was not interiorized by the absorptive cells. These findings suggest that although human absorptive cells have an endocytotic mechanism, possibly fluid-phase endocytosis, cell-coat glycoproteins are not taken up by the cells, as indicated by the absence of ferritin in the apical vesicles and tubules, as well as the lysosome-like bodies. These findings provide indirect support for our hypothesis that the lysosome-like bodies have a function in the regulation of cell-coat glycoprotein transport via a crinophagic mechanism (fusion of apical vesicles and tubules with lysosome-like bodies) rather than via an exocytotic-endocytotic mechanism.
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PMID:Endocytosis in absorptive cells of cultured human small-intestinal tissue: horseradish peroxidase, lactoperoxidase, and ferritin as markers. 722 1

The surface of dendritic cells (DC) has been analyzed by means of monoclonal antibodies (Ab) and lactoperoxidase (LPO)-mediated radioiodination. Antigens and other exteriorily disposed polypeptides of purified spleen DC were compared with those of tissue macrophages (Mphi), monocytes, and other bone marrow-derived elements. Quantitative binding studies and autoradiography with (125)I-Ab established that DC expressed high levels of I-A and H-2D, 2 x 10(5) and 1 x 10(5) Ab binding sites per cell, respectively. DC from conventional, germ-free, and specific pathogen-free mice were all rich in Ia. Expression of Ia on B cells was 5-10 percent of that on DC and increased fivefold during lipopolysaccharide mitogenesis. More than 70-90 percent of purified Mphi and monocytes from specific pathogen-free mice were Ia negative, but increased levels of Ia were noted on cells from mice reared under conventional conditions. Thus large amounts of Ia on DC is a constitutive trait, whereas the expression of Ia by other cell types may be governed by the environmental and immunological status of the host. The 2.4G2 Fc receptor Ag was not detected on DC. Peritoneal and spleen Mphi had 10(5) 2.4G2 binding sites/cell, whereas monocytes and lymphocytes were less reactive (1 x 10(4)-3 x 10(4) binding sites/cell). Four other Mphi-related antigens were evaluated. Each had a distinctive tissue distribution and none bound exclusively to Mphi and monocytes. Neither 1.21J (Mac-1) nor F4/80 reacted with DC. Immunoprecipitation studies of externally ((125)I) and biosynthetically ([(35)S]methionine)dabeled cells confirmed the binding data. Sensitive binding assays with (125)I-Ab confirmed previous observations that DC lack Ig and Thy-1. Lyt-1 was also not found on DC, but 5-12 percent of the cells in purified DC preparations expressed both Lyt-2 and Ia. All DC expressed the leukocyte common antigens at levels similar to other leukocytes. The spectrum of surface polypeptides labeled by LPO-mediated iodination was different on Mphi, DC, and lymphocytes. Polypeptides migrating at molecular weights of 155,000, 85,000, and 62,000 appeared to be restricted to DC. These observations establish that the cell surface of DC differs considerably from other leukocytes, including the blood monocyte, and suggest that the DC is part of a unique Ia-rich leukocyte differentiation pathway.
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PMID:Studies of the cell surface of mouse dendritic cells and other leukocytes. 725 26

We describe a method for the specific radioiodination of pinocytic vesicles (PVs) based upon the simultaneous endocytosis of lactoperoxidase (LPO) and glucose oxidase (GO). Initial experiments indicated that LPO was interiorized by the macrophage cell line J774 by fluid phase pinocytosis and without detectable binding to the plasma membrane (PM). Interiorization varied linearly with enzyme concentration and exposure time, was temperature dependent, and was undetectable at 4 degrees C. Employing EM cytochemistry, LPO activity was restricted to PVs after a 3- to 5-min pulse at 37 degrees C. These results formed the basis of the method for iodinating the luminal surface of PVs: 5-min exposure to both LPO and GO at 37 degrees C followed by washes and iodination (addition of 125I and glucose) at 4 degrees C. Enzyme-dependent incorporation of iodide into the polypeptides of both PV membrane and contents occurred. Several lines of evidence indicated that there was selective labeling of PV as opposed to PM. Iodination did not occur if the pinocytic uptake of LPO ad GO was inhibited by low temperature. EM autoradiography showed a cytoplasmic localization of grains, whereas a clear PM association was evident with surface labeling. LPO was iodinated only after PV labeling and was present within organelles demonstrating latency. After PV iodination, > 75% of several labeled membrane antigens could be immunoprecipitated by monoclonal antibodies only after cell lysis. In contrast, all labeled antigens were accessible to antibody on intact cells after surface labeling. The polypeptide compositions of PM and PV membrane were compared by SDS polyacrylamide gel electrophoresis and by quantitative immune precipitation using a panel of anti-J774 monoclonal antibodies. The electrophoretic profiles of iodinated proteins (15-20 bands) were strikingly similar in NP-40 lysates of both PV and PM iodinated cells. In addition, eight membrane antigens examined by immune precipitation, including the trypsin-resistant immunoglobulin (Fc) receptor and the H-2Dd histocompatibility antigen, were found to be iodinated to the same relative extents by both labeling procedures. We conclude that PV membrane is formed from a representative sample of PM polypeptide components.
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PMID:Selective iodination and polypeptide composition of pinocytic vesicles. 741 Apr 75

The effects of methanol, acetone, and ethylene glycol (up to 50% v/v) on elementary steps in the reactions of horseradish peroxidase (HRP) and lactoperoxidase (LPO) were studied by means of the stopped-flow method and the difference spectrum. The rate constant (k3,app) of the oxidation reaction of p-cresol with HRP compound II was remarkably reduced in the presence of organic solvents (to 2.3%, 1.8% and 9.4% of the original value in the presence of 50% (v/v) of methanol, acetone and ethylene glycol, respectively), then to a lesser degree were decreased the rate of the oxidation reaction with LPO compound II, and the rate of the oxidation reaction with HRP compound I. These reductions in the reaction rates were not due to competitive inhibition of the solvents, but considered to be related to the degree of exposure of the electron transfer route to the medium. While the rate constant of compound I formation (k1,app) was moderately affected by organic solvents in the case of HRP, the reaction rate with LPO was scarcely affected by organic solvents, being in harmony with the compact heme crevice which probably hampers penetration of solvent molecules. The rate constant (k2,i,app) of the oxidation reaction of an iodide ion by HRP compound I was also hardly affected by the solvents. On the basis of these facts, the mechanism of electron transfer from donors to compound I and compound II is discussed.
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PMID:Effects of mixed solvents on three elementary steps in the reactions of horseradish peroxidase and lactoperoxidase. 749 6

Concentrations of salivary antimicrobial factors are well documented in children and young adults, but little information is available on such defense factors in healthy elderly persons. We determined the levels of total IgA, total IgG, lysozyme, lactoferrin, myeloperoxidase, salivary peroxidase, amylase, sialic acid, and total protein in a group of 71 subjects aged 76, 81, and 86 yr, as well as their correlations to paraffin-wax-stimulated salivary flow rate. Participants were either unmedicated (n = 67) or using medicines with no oral significance (n = 4). Statistically significant negative correlations existed between flow rate and total IgA, lysozyme, lactoferrin, sialic acid, and total protein. Concentrations of sialic acid and salivary peroxidase were highest in the oldest age group. Total IgA concentration was higher in women than in men, although men showed higher concentrations of sialic acid and higher sialic acid/total protein ratios. Subjects with poor gingival health had higher concentrations of total protein than did those with no need for periodontal treatment. Edentulous subjects with complete dentures showed significantly lower concentrations of IgG, lactoferrin, and myeloperoxidase than did dentate subjects. Our results suggest that, when compared with data from previous studies, concentrations of salivary antimicrobial agents do not decline with age in unmedicated elderly people. However, defense factors which are derived also from gingival crevicular fluid are decreased in the absence of teeth.
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PMID:Antimicrobial factors, sialic acid, and protein concentration in whole saliva of the elderly. 751 65

Delmopinol is a new surface-active agent which can reduce plaque formation and gingivitis. This study was aimed to analyze whether delmopinol (0.0032-0.65 mM) interferes with the activity of two surface-active oral antimicrobial enzymes, salivary peroxidase and lysozyme. In addition to human whole saliva (pH 5.0 and 6.0), the experiments were done in 0.1 M phosphate buffer (pH 6.0) with purified lactoperoxidase (LPO) and myeloperoxidase (MPO). LPO and MPO were significantly inhibited in buffer by delmopinol concentrations > 6.5 mM and > or = 3.2 mM, respectively. No such inhibition was found for total peroxidase activity in mixed saliva. In vitro, delmopinol was found to desorb surface-bound peroxidases in an active form to the liquid phase. In further analyses, the possible effect of delmopinol on peroxidase-generated hypothiocyanite (HOSCN/OSCN-) was studied in saliva and buffer. No effect was found in buffer, but salivary HOSCN/OSCN- declined significantly with 6.5 mM delmopinol. This was obviously due to an enhanced decay of hypothiocyanite, rather than its reduced rate of formation. No delmopinol-related inhibition of lysozyme occurred in saliva or buffer. The results suggest that high concentration (6.4 mM -0.2%) of delmopinol may lower the concentrations of antimicrobial HOSCN/OSCN- in saliva but has no effect on human lysozyme.
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PMID:Effects of delmopinol on antimicrobial peroxidase systems and lysozyme in vitro and in human whole saliva. 755 57

During three lactational periods (start, middle and end of lactation) of 35 milk cows suffering from mastitis and compared with 34 healthy milk cows of comparable milk production the activity of lactoperoxidase (LPO) and the SCN-content of the milk in each udder quarter were determined. Both components showed no alterations in the subclinical form of the disease. There exists a decrease of the LPO activity in the secretion of ill udder quarters, which will be distinct only in the individual animal and a strong increase of the SCN-content, which is also significant in comparison with the milk of healthy cows.
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PMID:[Lactoperoxidase activity and thiocyanate content of milk from cows with mastitis in different lactation stages]. 764 26

The mechanism of suicidal inactivation of lactoperoxidase (LPO) by mercaptomethylimidazole (MMI) has been studied. Analogue studies indicate a specific requirement for the thiol group of MMI for inactivation of LPO in the presence of H2O2. MMI is oxidized via one-electron transfer by LPO compound II as demonstrated by a spectral shift from 430 to 412 nm through an isosbestic point at 421 nm. A decrease in Soret absorbance at 412 nm and the appearance of visible peaks at 592 and 636 nm are the characteristics of the inactivated enzyme. The one-electron oxidation product of MMI was identified by e.s.r. spectroscopy as the 5,5'-dimethyl-l-pyrroline N-oxide (DMPO) adduct of the sulphur-centred thiyl radical. Both inactivation and spectral change are prevented by the radical trap DMPO, suggesting involvement of the thiyl radical in inactivation. pH-dependent inactivation kinetics indicate the involvement of an ionizable group on LPO (pKa 6.1), deprotonation of which favours inactivation. The enzyme is protected by iodide and not by guaiacol, suggesting that MMI interacts at or near the iodide-binding site which is away from the aromatic-donor-binding site. The inactive enzyme can form compound II and bind aromatic donor, indicating that the MMI oxidation product does not attack haem iron or aromatic-donor-binding site. We suggest that MMI interacts at the iodide-binding site for oxidation and the reactive product, probably the thiyl radical, is incorporated into the adjacent electron-rich site of haem porphyrin to cause inactivation.
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PMID:Irreversible inactivation of lactoperoxidase by mercaptomethylimidazole through generation of a thiyl radical: its use as a probe to study the active site. 770 70

Thyroid peroxidase (TPO) autoantibodies are heterogeneous and have been classified in terms of whether they cross-react with myeloperoxidase (MPO), lactoperoxidase (LPO), or thyroglobulin (Tg) as well as by whether they inhibit TPO enzymatic activity. Four human monoclonal TPO autoantibodies, generated using combinatorial immunoglobulin gene libraries and expressed as F(ab), have been used to investigate these properties of TPO autoantibodies. The binding of F(ab) WR1.7, TR1.8, TR1.9, and SP1.4 to 125I-labeled recombinant TPO was inhibited 50% by approximately 10(-10) mol/L unlabeled TPO, reflecting the high affinities of these F(ab) for TPO. In contrast, F(ab) binding to TPO was unaffected by human MPO (both native and reduced), bovine LPO, or human Tg at concentrations up to 10(-8) mol/L. Further, TPO enzymatic activity, measured by guiacol oxidation, was unaffected by preincubation with the four F(ab) individually or as a pool (each at 10(-8) mol/L). In conclusion, four human TPO monoclonal autoantibodies do not cross-react with related peroxidases or Tg, nor do they inhibit TPO enzymatic activity. These monoclonal immunoglobulin G class autoantibodies define the immunodominant region on TPO and represent about 85% of TPO autoantibodies in an individual patient's serum. Consequently, our data suggest that TPO autoantibodies that cross-react with MPO, LPO, or Tg, or inhibit TPO enzymatic activity are likely to bind outside the immunodominant region.
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PMID:Human monoclonal autoantibodies against the immunodominant region on thyroid peroxidase: lack of cross-reactivity with related peroxidases or thyroglobulin and inability to inhibit thyroid peroxidase enzymatic activity. 771 25


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