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 chemical modification of bacterial components was studied following incubation of Escherichia coli with the peroxidase-hydrogen peroxide (H(2)O(2))-iodide (I(-)) antimicrobial system or with iodine (I(2)). The oxidation of cell sulfhydryls and the iodination of cell components were measured. Both the peroxidase system and I(2) oxidized sulfhydryls. When the I(-) concentration in the peroxidase system was greater than 100 muM, the peroxidase system and I(2) were equivalent. That is, sulfhydryl oxidation or killing per mole of H(2)O(2) equaled that per mole of I(2). These results were consistent with peroxidase-catalyzed oxidation of I(-) to yield 1 mol of I(2) per mol of H(2)O(2). Sulfhydryls were oxidized to yield sulfenic acids and free I(-). With I(-) concentrations in the range of 10 to 100 muM, the amount of sulfhydryls oxidized by the peroxidase system could exceed the amount of I(-). Because the oxidation of sulfhydryls to sulfenic acids did not consume I(-), one I(-) ion could participate in the oxidation of many sulfhydryls. With I(-) concentrations lower than 10 muM, complete oxidation of sulfhydryls was not obtained. Incorporation of I(-) into iodinated derivatives of bacterial components partly depleted the system of I(-) and limited the formation of I(2). These results indicated that antimicrobial activity was due to peroxidase-catalyzed oxidation of I(-) to I(2), followed by I(2) oxidation of cell components. There was a direct relationship between sulfhydryl oxidation and antimicrobial action. Although iodination of bacterial components accompanied sulfhydryl oxidation, the amount of I(-) incorporation was not directly related to antimicrobial action. Also, incorporation of I(-) interfered with antimicrobial action at low I(-) concentrations.
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PMID:Oxidation of Escherichia coli sulfhydryl components by the peroxidase-hydrogen peroxide-iodide antimicrobial system. 35 15

Membrane vesicles can be obtained from epimastigote forms of Trypansoma cruzi by incubating cells with either cross-linking reagents or acid pH. Acetate, phtalate or citrate, at pH 4.0, but not at higher pH values, were able to induce plasma membrane vesiculation. Vesicles have been purified by sucrose density centrifugation and their membrane origin was demonstrated by the following criteria: (a) Vesicles are 5--10 times richer in protein-bound iodine when they are prepared from cells previously labeled with 131I by the lactoperoxidase catalyzed reaction. (b) Electron microscopy of vesiculating cells shows physical continuity between cell plasma membrane and vesicle membrane. (c) Antibodies prepared against purified vesicles are able to agglutinate epimastigote forms of T. cruzi with sera dilutions up to 1 : 256 to 1 : 512. (d) Freeze-fracture studies of the purified vesicles have shown images of faces P and E compatible with known images of the intact cell plasma membrane. Typical preparations of acetate vesicles present the following characteristics: total carbohydrate : protein=1.5--2.0; orcinol : protein-0.07 and absence of diphenylamine reaction. Vesicles contain 0.2--0.5% and 0.3--1.0% of the total homogenate protein and carbohydrate, respectively. The presence of 10 major protein bands and 30--50-fold enrichment of the four sugar-containing macromolecules present in epimastigote forms of T. cruzi have been demonstrated in these preparations.
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PMID:Plasma membrane vesicles isolated from epimastigote forms of Trypanosoma cruzi. 36 44

At the time of fertilization, sea urchin eggs release a peroxidase which, together with H2O2 generated by a respiratory burst, is responsible for hardening of the fertilization membrane. We demonstrate here that the ovoperoxidase of unfertilized eggs is located in cortical granules and, after fertilization, is concentrated in the fertilization membrane. Fertilization of sea urchin eggs or their parthenogenetic activation with the ionophor A23187 also results in (a) the conversion of iodide to a trichloroacetic acid-precipitable form (iodination), (b) the deiodination of eggs exogenously labeled with myeloperoxidase and H2O2, (c) the degradation of thyroxine as measured by the recovery of the released radioiodine at the origin and in the inorganic iodide spot on paper chromatography, and (d) the conversion of estradiol to an alcohol-precipitable form (estrogen binding). The iodination reaction and the binding of estradio occurs predominantly in the fertilization membrane where the ovoperoxidase is concentrated. From the estimation of the kinetics of incorporation of iodine, we determine that the peroxidative system is active for 30 min after fertilization, long after hardening of the fertilization membrane is complete. Most of the bound iodine is lost during the hatching process. Iodination of albumin is catalyzed by the material released from the egg during fertilization, when combined with H2O2 and iodide. Iodination, thyroxine degradation, and estradiol binding are inhibited by azide, cyanide, aminotriazole, methimazole, ascorbic acid and ergothioneine, all of which can inhibit peroxidase-catalyzed reactions. These responses of the sea urchin egg to fertilization are strikingly similar to the changes induced in polymorphonuclear leukocytes by phagocytosis and, in both instances, a peroxidative mechanism may be involved.
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PMID:Metabolic similarities between fertilization and phagocytosis. Conservation of a peroxidatic mechanism. 37 84

This paper describes the evaluation of a heterologous enzyme immunoassay for the determination of total thyroxine in serum by a group of seven clinical chemical laboratories. The test follows the principles of the enzyme linked immunosorbent assay (ELISA) and uses peroxidase as a marker. The evaluation of analytical reliability yielded the following results within the analytical range from 39 unto 322 nmol/l: 1. Within-batch precision ranged from 3.1 unto 10.4% (coefficient of variation) with single analyses. 2. Between-batch precision ranged from 3.7 unto 20.4% with single analyses. 3. Between-laboratories precision ranged from 5.4 unto 6.8%. 4. Pure thyroxine, added to serum or thyroxine-free serum, gave recoveries between 93 and 120%. 5. Analysis of control sera gave results essentially comparable to the assigned values based upon radioimmunoassays. 6. Analysis of 288 clinical sera gave slightly higher results by the enzyme immunoassay than by the analogous radioimmunoassay from the same manufacturer. 7. Comparison with other methods of analysis (radioimmunoassays, competitive protein ligand assays, hormonal iodine assay) yielded partly comparable, partly higher results. 8. Comparison with the homogenous enzyme immunoassay (EMIT) led to comparable results. 9. Interference due to hyperlipemia or hemolysis was not observed. 10. There might be an interference in hyperbilirubinaemic sera, due to an as yet unknown factor. With respect to practicability the ELISA-test compares favourably with the analogous solid phase radioimmunoassay. The main differences are the absence of radioactive material and a longer shelf-live of reagents. Following the manual procedure the time taken to perform the enzyme immunoassay is slightly longer than for the analogous radioimmunoassay.
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PMID:[Determination of thyroxine in serum by a heterogeneous enzyme immunoassay: results of a joint trial]. 38 82

The effects of the administration of xylitol on the biochemical properties of monkey parotid and submandibular saliva and lacrimal fluid were investigated. Monkeys (Macaca mulatta) were fed either a sucrose or xylitol diet for 3 days. Ingestion of xylitol was associated with a significant increase of the activity of the salivary lactoperoxidase. The concentration of protein was also increased. Higher lactoperoxidase activity was found in parotid than in submandibular saliva. The concentrations of inorganic phosphate, calcium and SCN ions were practically unaffected. The concentration of SCN ions in pilocarpine stimulated monkey saliva was low (less than 5.5 mg/liter). Peroral administration of 2.5 g of xylitol or sorbitol per day to M. fascicularis resulted in almost similar levels of salivary lactoperoxidase activity. The administration of xylitol orally or by gastric intubation was not found to affect the concentration of lactoperoxidase, protein, phosphate, and SCN and iodine ions in lacrimal fluid. The results suggest that specific dietary sugars have a selective effect on the biochemical properties of saliva.
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PMID:Effect of peroral administration of xylitol on exocrine secretions of monkeys. 41 56

Cells infected with a temperature-sensitive mutant (ts-26) of Rauscher murine leukemia virus (R-MuLV) or with wild-type virus were labeled with 35S-methionine, and cell extracts were examined for radioactive polypeptides which could be precipitated by monospecific antisera to viral proteins. When shifted from permissive (31 degrees C) to nonpermissive (39 degrees C) temperature, cells infected with ts-26 rapidly begin to accumulate gPr90enr, the glycoprotein precursor to the membrane envelope glycoprotein gp70 and to the membrane-associated protein p15E. Simultaneously, formation of these mature virion proteins ceases. In addition, lactoperoxidase-catalyzed surface labeling with 125I--iodine indicates that the plasma membrane of cells infected with ts-26 becomes depleted of gp70 antigens at 39 degrees C. Nevertheless, at 39 degrees C these cells release defective MuLVs which lack gp70 and p15E but contain an outer membrane. The released particles also contain an aberrantly processed form of the major virion core protein p30, and many of these virion cores have an unusual immature crescent shape. It has previously been reported that cells infected with the ts-26 mutant of R-MuLV process a 65,000 dalton precursor (Pr65gag) of the virion core proteins more slowly at 39 degrees C than do cells infected with wild-type virus (Stephenson, Tronick and Aaronson, 1975). Although we have confirmed these results, this effect is relatively small and it is known that various alterations of MuLV assembly can lead secondarily to inhibited processing of Pr65gag. We propose that the ts-26 mutant has a primary temperature-sensitive defect in membrane glycoprotein synthesis and that this change causes pleiotropic effects on core morphogenesis.
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PMID:A murine leukemia virus mutant with a temperature-sensitive defect in membrane glycoprotein synthesis. 42 Dec 71

The effects of the antithyroid goitrogens, methylthiouracil and methylmercaptoimidazole, on the oxidation of N-acetyltyrosylamide at pH 8.8 by lactoperoxidase have been evaluated in the presence and the absence of iodide for the purpose of elucidating the effects of iodide. At pH 8.8, iodine is not oxidized. In the absence of iodide, the two antithyroid drugs inactivate lactoperoxidase by a second order process. When iodide is added before methylthiouracil or methylmercaptoimidazole, enzyme inactivation does not occur as rapidly and both goitrogens are readily oxidized. The kinetics of the oxidation reactions have been analyzed in order to obtain the equilibrium constant of the iodide . lactoperoxidase complex. Essentially the same iodide dissociation constant, i.e. 2 x 10(-5) M, was found by studying its effects on the kinetics of oxidation of the two antithyroid drugs. A large difference absorption spectrum is observed in the Soret region between native lactoperoxidase and lactoperoxidase inactivated by methylthiouracil.
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PMID:Iodide binding and regulation of lactoperoxidase activity toward thyroid goitrogens. 42 80

The influence of the physical state of the membrane lipid matrix on the vertical disposition of membrane proteins was studied with Acholeplasma laidlawii. Changes in membrane fluidity were brought about by altering the fatty acid composition of membrane lipids, by changing the growth temperature, by aging of cultures and by inducing changes in the membrane lipid-to-protein ratio through treatment with chloramphenicol. The lactoperoxidase-mediated iodination technique was used to label membrane proteins exposed to the aqueous surroundings. The degree of exposure of the iodine-binding sites of membrane proteins on the external surface of intact cells was found to undergo significant changes on varying growth conditions, but the changes could not be consistently correlated with changes in membrane fluidity, nor were they discernible on iodination of isolated membranes.
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PMID:Is the vertical disposition of Mycoplasma membrane proteins affected by membrane fluidity? 44 13

Radioiodination reportedly damages peptides, but the nature of the damage has not been adequately examined. Utilizing isoelectric focusing, we examined the products of Chloramine T- and lactoperoxidase-directed radioiodinations of human calcitonin. Initially, the reaction products were purified by adsorption onto and elution from microfine silica (QUSO-G32). Radioiodination of the calcitonin by Chloramine T and lactoperoxidase produced a heterogeneous population of 125I-labeled peptides exhibiting apparent isoelectric points that were more acidic than that of unlabeled synthetic calcitonin. Variation in the products among radioiodinations and the inability of QUSO-G32 to resolve the components of the reaction mixture prompted our examination of alternative purification procedures. Anion-exchange chromatography on QAE-Sephadex effectively separated [125I]diiodotyrosine containing calcitonin from free iodine and [125I]iodolactoperoxidase. Our data indicate that: (a) radioiodination of human calcitonin by Chloramine T and lactoperoxidase induced alteration in the peptide as evidenced by isoelectric point, (b) specific [125I]iodopeptides vary in incidence and relative abundance among radioiodinations, (c) identification of the labeled amino acid in [125I]iodopeptides cannot ensure intergrity of the molecule, and (d) isoelectric focusing provides a method of comparing the products of peptide radioiodinations among laboratories.
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PMID:Heterogeneity of chloramine T- and lactoperoxidase-radioiodinated human calcitonin. 44 36

Pig thyroid slices were incubated with Na131I and the 17--19S 131I-labeled thyroglobulin isolated was subjected to dissociation with 0.3 mM sodium dodecyl sulphate SDS) on sucrose density gradient centrifugation and to iodoamino acid analysis. During the incubation, initially dissociable thyroglobulin was gradually altered to 0.3 mM SDS-resistant species with increasing incorporation of iodine. Microsome-bound, poorly iodinated thyroglobulin and preformed thyroglobulin were chemically iodinated and then subjected to analysis of dissociability and iodoamino acid contents with newly incorporated iodine. The results indicated that the behavior of the former thyroglobulin resembled that of 131I-thyroglobulin obtained from the slices. Then, thyroid slices were incubated for 3 min with Na131I and 3H-leucine with or without 10-min chase incubation. The sucrose density gradient centrifugation patterns of 131I and 3H-radioactivity of cytoplasmic extracts indicated that 131I-thyroglobulin is contained in particulates, especially in vesicles with low density(d=1.12) and that some of them are released into the soluble fraction within 10 min. The vesicles contained peroxidase and NADH-cytochrome c reductase, and are probably exocytotic vesicles in the apical area of cytoplasm of follicular cells. No positive evidence was obtained that plasma membranes participate in the iodination of thyroglobulin under the present experimental conditions. These results suggest that, in the incubation of thyroid slices, iodine atoms are preferentially incorporated into newly synthesized, less iodinated thyroglobulin, rather than preformed thyroglobulin, and that the iodination occurs, at least to a certain degree, in apical vesicles before the thyroglobulin is secreted into the colloid lumen.
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PMID:Process of iodination of thyroglobulin and its maturation. I. Properties and distribution of thyroglobulin labeled with radioiodine in pig thyroid slices. 45 25


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