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)

Children with protein calorie malnutrition have impaired immune functions. Immunoglobulin levels are low in children with severe protein deprivation, but are not affected in moderate or borderline protein malnutrition. Specific antibody response is either normal or reduced depending on the antigen used. Involution of the thymus dependent lymphatic system and severe impairment of the cell-mediated immune reactions are prominent features in children with kwashiorkor. Furthermore, in vitro granulocyte dysfunction in those children has been demonstrated as far as chemotaxis, microbiocidal activity and quantitative leucocyte iodination is concerned. There is a delayed chemotactic response in the early incubation intervals; there is decreased killing of S. aureus, E. coli and C. albicans after 60 minutes of incubation, and there is less iodination by phagocytising granulocytes of kwashiorkor children than in control experiments, indicating an impairment of the myeloperoxidase-peroxide-iodide mediated killing system. The possible clinical implications of these in vitro findings are briefly discussed.
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PMID:Immunological aspects of infantile protein-calorie malnutrition. 82 70

The conversion of iodide to a trichloroacetic acid-precipitable form (iodination) by polymorphonuclear leukocytes (PMN's) has been re-evaluated as a measure of neutrophil function. Optimum conditions are described which result in an iodination value for normal cells during the phagocytosis of zymosan of 64.1 +/- 13.2 (S.D.) nmol. per 10(7) PMN's per hour. Iodination is inhibited by agents which decrease phagocytosis, inhibit myeloperoxidase-catalyzed reactions, or degrade H2O2 and is stimulated by superoxide dismutase, an enzyme which catalyzes the conversion of the superoxide anion to oxygen and H2O2. When patients' cells and normal serum are employed, the iodinating capacity of the patients' cells is evaluated. It is low in patients with myeloperoxidase deficiency and chronic granulomatous disease, and an intermediate value was observed in a carrier of chronic granulomatous disease. When normal cells and patients' serum are employed, the iodination reaction is an indirect measure of the opsonic activity of the patients' serum. The decreased opsonic activity for zymosan of human sera deficient in the fourth or third component of complement was demonstrated in this way. Thus measurement of iodination is a convenient and sensitive screening test for cellular or humoral abnormalities of the phagocytic process.
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PMID:Iodination by human polymorphonuclear leukocytes: a re-evaluation. 83 26

Conventional protein iodination involves the addition of an oxidizing agent to the protein solution. Through the use of the acylating agent N-succinimidyl-3(4-hydroxyphenyl)propionate, labeling can be accomplished without subjecting the protein to oxidizing conditions. Fibrinogen and serum albumin labeled with 131I and 77Br by this technique were compared with each other and with 125I-protein prepared by direct iodination using the ICI, chloramine-T, and lactoperoxidase methods. Iodinated proteins have two drawbacks: the high radiation dose accompanying 125I and 131I, and the ease of hydrolysis of the weak carbon-iodine bond. These drawbacks can be overcome by using 56-hr 77Br.
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PMID:In vitro stability and in vivo clearance of fibrinogen or serum albumin labeled with 77Br, 131I, or 125I by direct or indirect synthetic methods. 83 78

A radioimmune assay for the antitumor agent, macromomycin, using purified, radioiodine-labeled macromomycin and antisera raised in rabbits against a carbodiimide-catalyzed macromycin-Limulus polyphemus hemocyanin complex has been developed. Radiolabeled macromomycin was prepared by direct iodination of the polypeptide antibiotic with the use of iodine monochloride or solid-state lactoperoxidase. Antibody-bound drug was isolated from free macromomycin with dextran-coated, activated charcoal. The standard curve of the sequential saturation assay was linear on a logit-log plot and indicated a lower limit of sensitivity of approximately 100 pg macromomycin. The radioimmune assay was suitable for measuring macromomycin in the presence of other antitumor drugs, and detection of macromomycin was quantitative when it was added to normal human serum or urine. Drug binding to melanoma and mammary carcinoma cell surfaces could be inhibited by preincubating macromomycin with affinity-purified antimacromomycin antibodies. However, once the drug was bound to cell surfaces, addition of antimacromomycin antibodies did not result in removal of the drug from cell surfaces or in reversal of macromomycin-induced inhibition of thymidine incorporation into cellular DNA. Antimacromovide useful tools for developing pharmacokinetic and toxicity studies of macromomycin, as well as for analyzing the mechanism(s) of action of the drug.
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PMID:Radioimmune assay and characteristics of antibodies to macromomycin (NSC 170105). 84 45

The effect of ionic strength on the proteolysis by trypsin of the major membrane-penetrating protein (polypeptide 3) in the erythrocyte membrane was studied. Both the intracellular and extracellular regions of the protein are susceptible to trypsin proteolysis under hypo-osmotic conditions, whereas under iso-osmotic conditions the extracellular region of the protein is resistant to trypsin, and the intracellular region yields only two cleavage products with trypsin. Studies of the fragments obtained from polypeptide 3 by trypsin digestion under iso-osmotic conditions of 'ghosts' radioiodinated with lactoperoxidase confirmed our earlier conclusions that the polypeptide chain of polypeptide 3 traverses the membrane twice. Ionic-strength-dependent changes were also observed in the incorporation of iodine by lactoperoxidase into the individual extracellular tyrosine sites of the protein. These results show that polypeptide 3 undergoes ionic-strength-dependent changes in structure.
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PMID:Ionic-strength-dependent changes in the structure of the major protein of the human erythrocyte membrane. 85 15

Glucagon was iodinated with the lactoperoxidase method at pH 10.0 in the presence of propylene glycol using a substitution of 0.3 g-atom I/mol glucagon. Under these conditions the reactivity of the iodine to tyrosine at position 13 is found to be 4-fold that of the tyrosine at position 10. The amount of diiodotyrosine was less than one-twentieth that of the monoiodotyrosine at either tyrosine residue. Relatively pure monoiodo[125I]tyrosine-13-glucagon can be separated from other iodoglucagons by means of DEAE-chromatography. Such a homogeneous preparation with a known position of the iodine makes it possible to study a specific interaction between the monoiodoglucagon and the glucagon antisera or the glucagon receptor.
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PMID:Preparation of monoiodotyrosine-13-glucagon. 85 7

The synthesis and organization of Sindbis virus structural proteins was investigated in BHK cells infected with wild-type virus (SVHR) or temperature-sensitive (ts) mutants defective in maturation. Cells infected with ts-23 or ts-20 (complementation groups D and E) were similar in the polypeptides synthesized at the nonpermissive temperature and differed from SVHR-infected cells in that the envelope protein E2 was not cleaved from the PE2 precursor. Data from experiments utilizing pulse-chase procedures or protein synthesis inhibitors indicated that although infectious virions were released from cells infected with these mutants in shift-down experiments, the particles were produced almost exclusively from proteins synthesized after the return to permissive temperature. This suggests that a stable complex may be formed among the structural proteins before budding. A membrane fraction isolated from cells infected with either ts mutants or SVHR contained the PE2, E1, and C polypeptides, whereas E2 was restricted to fractions obtained from SVHR-infected cells. Although equivalent amounts of virus-specific protein were synthesized in cells infected with either mutant and the cells contained qualitatively the same proteins in the isolated membranes, cells infected with ts-23 did not have virus-specific proteins exposed on their surface that could be detected by ferritin-conjugated antibody-labeling procedures or lactoperoxidase-mediated iodination. In contrast, ts-20-infected cells had significant amounts of viral protein, mainly E1, that could be detected on the plasma membrane by either procedure. Iodine was incorporated into E1 and E2 on the surface of SVHR-infected cells in the same relative amounts as seen in iodinated virions. PE2, however, although present in membranes, could not be iodinated on the surface of infected cells under any of the conditions used in this study. We also monitored the relative efficiency with which these viral proteins could be removed from intact cells by dilute solutions of nonionic detergents. The results indicated that E2 was most efficiently removed, followed by E1. PE2 (the precursor to E2) and C remained associated with the cell and could be subsequently isolated in the membrane fraction.
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PMID:Envelopments of Sindbis virus: synthesis and organization of proteins in cells infected with wild type and maturation-defective mutants. 87 34

A procedure for isolation of stabilized preparations of peroxidase, covalently bound with AH-Sepharose 4B by the enzyme carbohydrate residues, which had been previously oxidized by iodine acid, is proposed. The catalytic properties and thermostability of soluble oxidized and immobilized peroxidase has been studied and a comparison of these properties with those of the native enzyme has been made. It has been demonstrated that the oxidation of the carbohydrate residues dose not affect eh Km value for soluble oxidized peroxidase, but leads to a decrease in the kcat approximately two times for the reaction of peroxidase exidation of o-dianizidine. In case of immobilized peroxidase the Km value for H2O2 does not change, whereas the Km value for o-dianizidine is decreased approximately 20 times. It is demostrated that the chemical structure of the matrix surface and in case of the same matrix used--the degree and type of modification of the functional groups of protein, have a strong effect on the stability of the immobilized enzyme.
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PMID:[Catalytic properties and thermostability of horseradish peroxidase covalently bound with Sepharose by carbohydrate residues of the enzyme]. 88 67

It was observed in the present investigation that labeled thyroxine (T4) comprised less than 2% of the total 131I in the thyroids of severely iodine-deficient rats labeled with 131I for 18-24 h, a much lower value than had previously been reported for iodine-deficient rats. This low value was attributable to two factors: 1) the use of a diet low enough in iodine content to produce extreme iodine deficiency, and 2) the use of a paper chromatography system that successfully separates T4 from the minor iodothyronines, 3,3'-diiodothyronine (T2) and 3',5',3-triiodothyronine (reverse T3; T3'). Formation of the minor iodothyronines, while low, becomes appreciable in relation to T4 formation in severe iodine deficiency. In the present study, the formation of labeled T2 was significant only in iodine deficiency, and the highest values were observed in the most severely iodine-deficient rats. In the latter, labeled monoiodotyrosine (MIT) comprised approximately 60% of the total 131I in the thyroid, and the increased formation of T2 could be attributed to the increased probability of coupling between two molecules of MIT. The formation of labeled T3', on the other hand, was significant in thyroids from both iodine-deficient and iodine-sufficient rats. Similarly, in thyroglobulin iodinated in vitro with thyroid peroxidase to varying levels of iodination, the formation of T2 was evident only at lower levels of iodination, whereas the formation of T3' was significant at all levels of iodination. The comparison of relative T3' and T4 formation in enzymatically iodinated thyroglobulin with corresponding values reported for the intermolecular (DIHPPA) model for T4 formation, indicates that the peroxidase model system simulates much more closely the relative formation of T3' and T4 seen in vivo.
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PMID:Formation of 3,3'-diiodothyronine and 3',5',3-triiodothyronine (reverse T3) in thyroid glands of rats and in enzymatically iodinated thyroglobulin. 93 97

The evolution of peroxidase activity was followed during the course of iodine deficiency in the rat. The enzymatic activity was determined in vitro by oxidation of iodide or by iodination of bovine serum albumin using a peroxide-generating system. An inverse relationship between the stable iodine content in the gland and the peroxidase activity is observed; this relation is not linear and the highest increase is found when the iodine content in the gland is below 5 mug per thyroid gland, at 35 days of the treatment. In animals maintained on a low iodine diet, a triphasic effect on enzymatic activity is observed: early (10 and 20 days) and late (70 and 80 days) effects when the increase in peroxidase activity is 3 times higher than the increase in weight, DNA and total protein content; and an intermediar effect (between 20 and 70 days) when the peroxidase activity says approximately at the same level. In any case, the enzymatic activity increases to a greater extent than do thyroid weight, and total protein and DNA content, suggesting that high cellular activity is due to a specific enzyme induction comparable to that we obtained recently in human sporadic goitre.
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PMID:Thyroid peroxidase activity in iodine deficient rats. 94 27


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