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)

A new technique for the cytochemical demonstration of peroxidase is presented. Monomeric homovanillic acid is converted by H2O2 and peroxidase into its dimeric form, which is then precipitated as a complex salt of lead and rhodamine 6G or rhodamine B. The reaction product can be visualized by conversion to lead sulphide or viewed directly under the fluorescence microscope, since it emits a red fluorescence when excited with green light. The reaction is rapid and results in good localization at the cytologic level of peroxidase activity in granulocytes. The technique can be applied for the ultrastructural localization of enzymatic activity, but in its present form it does not match the localization sharpness of the diaminobenzidine method. This fluorescent cytochemical technique will also detect horseradish peroxidase activity and may provide a usefull probe in peroxidase immunohistochemistry. The principle of complexing metal salts with fluorescent dyes may find a more general application in enzyme cytochemistry.
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PMID:A new method for the cytochemical demonstration of peroxidase for light, fluorescence and electron microscopy. 76 73

The association constants for the binding of bilirubin to human serum albumin (HSA) have been determined at four different temperatures by measurements of the rate of the peroxidase catalyzed oxidation of unbound bilirubin. The change of enthalpy is determined from a van't Hoff plot (ln Kass versus 1/T) to about -13.5 kcal/mol. deltaG degrees is calculated from the binding constants, and deltaS degrees is obtained from: deltaG degrees = deltaH degrees--TdeltaS degrees. The results show that the large negative deltaG degrees (--11 kcal/mol) for binding of bilirubin to HSA is a consequence of the negative deltaH degrees. The entropy was found to be about--8.5 cal/mol/degree and tends to diminish the numerical value of deltaG degrees. The binding constant has also been determined at varying ionic strength. The results show a decrease in binding for increasing salt concentration. The data from the two sets of experiments suggest that hydrogen bonds and salt linkages rather than hydrophobic interactions are the main factor in the binding of bilirubin to its primary site on HSA.
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PMID:Studies of the affinity of human serum albumin for binding of bilirubin at different temperatures and ionic strength. 84 42

An improved method is described for the enumeration of lymphocyte surface markers in whole peripheral blood using reagents labelled with alkaline phosphatase. A suspension of washed whole blood is exposed to the labelled reagents and then smeared on slides. Endogenous peroxidase in monocytes is detected by the diaminobenzidine reaction amplified by osmication, and this identifies more cells than are recognised as monocytes by morphological criteria in Romanovsky-stained films. Lymphocytes are identified as peroxidase-negative mononuclear cells and those binding alkaline phosphatase-labelled reagents are demonstrated by treating the smears with naphthol ASMX phosphoric acid and fast red TR salt. By avoiding the loss of lymphocytes which is inevitable in any procedure for isolation of mononuclear cells from the blood, and by permitting elimination of monocytes from the counts, this method enables the proportion and absolute number of different circulating lymphocyte populations to be accurately enumerated. In the peripheral blood of seventeen normal individuals alkaline phosphatase rabbit F(ab)'2 anti-human immunoglobulin stained the following numbers (mean +/- s.d.) of lymphocytes, 9-0 +/- 1-5%, 214 +/- 66/microliter (B cells), and specific rabbit anti-T-cell serum followed by alkaline phosphatase goat F(ab)'2 anti-rabbit immunoglobulin stained 77 +/- 3%, 1846 +/- 488/microliter (T cells). The method, which is applicable to any surface marker which can be detected on living cells in suspension with a soluble reagent, provides permanent preparations which are counted in an ordinary light microscope and permits the use of counterstaining to reveal cellular morphology. Provided that appropriate specific reagents are available it is therefore suitable for routine clinical application.
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PMID:Enumeration of lymphocyte populations in whole peripheral blood with alkaline phosphatase-labelled reagents. A method for routine clinical use. 89 Oct 32

Extraction of membrane proteins from erythrocytes into sonicated phosphatidylcholine vesicles is described. In a process involving phospholipid and neutral lipid exchange, cell membrane proteins associate with the vesicles and can be separated from the cells by centrifugation. The protein transfer appears to be reversible; phospholipid vesicles mediate the delivery of small amounts of previously extracted protein into cell membranes. Prior to extraction, all but one of the proteins are accessible to lactoperoxidase iodination, and lipid analysis indicates that primarily the outer monolayer of the cell is involved in phospholipid exchange. Among the extracted proteins is acetylcholinesterase which is removed much more efficiently by this procedure than by concentrated salt solutions. The most abundant proteins of the erythrocyte membrane are not represented in the vesicle extract.
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PMID:Selective extraction of membrane-bound proteins by phospholipid vesicles. 89 40

A Peroxidase (EC 1.11.1.7) of the basidiomycet Phellinus igniarius was derived from mycel and a medium containing glucose and extract of yeast by using various methods of preparation. The enzyme resists extreme conditions (pH, temperature salt concentration). Its optimum pH for activities is in the acid range. Two isoenzymes were found. The molecular weight, isoelectric point, Michaelis-Menten constant, indolacetic acid oxidase activity and spectral and analytical properties of this peroxidase were determined. It is assumed that the enzyme has an intracellular as well as an extracellular field of activity.
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PMID:[Purification and characterization of peroxidase from Phellinus igniarius (author's transl)]. 96 69

A rapid and sensitive method is described for the quantitative determination of H202 produced by phagocytizing human granulocytes. For this purpose, the method of Keston and Brandt was mechanized, which is based on the oxidation of nonfluorescent leukociacetyl-2,7-dichlorofluorescein to a fluorescent compound by H202 in the presence of peroxidase. The optimal conditions for this test were determined. H202 in water can be measured in the range of 0.05 to 0.5 muM, with a standard deviation of 1.2 per cent at 0.4 muM (n = 1-). The production of H2O2 by phagocytizing granulocytes could only be measured in a medium which contained phosphate-buffered salt, albumin, glucose, NaN3, and IgG-coated latex particles. The fluorescence signal was catalase-sensitive. Of known amounts of H202, added to this medium, 97 per cent were recovered. Under optimal conditions we found a H2O2 production of 970 plus or minus 170 mumoles per 10-10 cells per hour (10 different healthy donors), corresponding to 50 to 70 per cent of the observed increase in O2 consumption. No H2O2 was produced by phagocytizing granulocytes from 2 patients with chronic granulomatous disease, while intermediate values were found in the cells from heterozygotes.
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PMID:Production of hydrogen peroxide by phagocytizing human granulocytes. 111 12

The characteristics of cell adsorption and pinocytotic uptake of diphtheria toxin by several mammalian cell types were studied. Purified toxin iodinated by a solid-state lactoperoxidase method provided preparations of high specific activity and unaltered biological activity. Dephtheria toxin-sensitive HEp-2 cells and guinea pig macrophage cultures were compared with resistant mouse L-929 cells. At 37 C the resistant cells in monolayer adsorbed and internalized [125I] toxin to a greater extent than did the HEp-2 cell cultures; no significant differences were observed at 5 C. Ammonium chloride protection levels did not alter uptake of toxin by either L-929 OR HEp-2 cells. Biological activity of the iodinated toxin, however, was negated provided the presence of ammonium chloride was maintained. The ammonium salt appears to maintain toxin in a state amenable to antitoxin neutralization. Guinea pig macrophages internalized iodinated toxin to a level 10 times greater than the established cell lines. In spite of the increased uptake of toxin by the endocytic cells, ammonium chloride prevented expression of toxicity. In an artificial system, toxin adsorbed to polystyrene latex spheres and internalized by guinea pig macrophages during phagocytosis did express biological activity. Ammonium chloride afforded some but not total protection against toxin present in the phagocytic vacuoles. The data suggest that two mechanisms of toxin uptake by susceptible cells may be operative. Toxin taken into the cell by a pinocytotic process probably is not ordinarily of physiological significance since it is usually degraded by lysosomal enzymes before it can reach cytoplasmic constituents on which it acts. When large quantities of toxin are pinocytized, toxicity may be expressed before enzymatic degradation is complete. A more specific uptake involving direct passage of the toxin through the plasma membrane may be the mechanism leading to cell death in the majority of instances.
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PMID:Interaction of cultured mammalian cells with [125I] diphtheria toxin. 112 Jun 9

The selectively-bred substrains of spontaneously hypertensive rats with a greater vulnerability to vascular lesions rapidly developed arterial fat deposition within 1 or 2 weeks as well as a greater hypercholesterolemic response when fed on high fat cholesterol diet including 20% of suet, 5% of cholesterol and 2% of cholic acid. The ring-like arterial fat deposition at the branches of superior mesenteric arteries and cerebrobasal arteries, which was found to be good indices for the deposition of intrarenal or coronary arteries, was not observed in normotensive rats fed on high fat cholesterol diet for 3 months, greatly delayed in SHR under antihypertensive treatment and accelerated by 1% salt loading in drinking water. The horseradish peroxidase infused intravenously 1 to 4 hours before sacrifice leaked in ring-like forms which corresponded to the fat deposit in mesenteric arteries. The incorporation of 3H-proline infused 4 hours before sacrifice was enhanced in the mesenteric arteries with the fat deposition. These results clearly indicated that hypertension was a great contributory factor to rapid arterial fat deposition, which was caused by an increased vascular permeability and enhanced the arterial collagen formation, the initiation process of arterio- or atherosclerosis.
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PMID:Pathogenesis of acute arterial fat deposition in spontaneously hypertensive rats. 115 92

A 3-dimensional model of lignin peroxidase (LiP) was constructed based on its sequence homology with other peroxidases, particularly cytochrome c peroxidase, the only protein with a known crystal structure in the peroxidase family. The construction of initial conformations of insertions and deletions was assisted by secondary structure predictions, amphipathic helix predictions, and consideration of the specific protein environment. A succession of molecular dynamics simulations of these regions with surrounding residues as constraints were carried out to relax the bond lengths and angles. Full protein molecular dynamics simulations with explicit consideration of bound waters were performed to relax the geometry and to identify dynamically flexible regions of the successive models for further refinement. Among the important functionally relevant structural features predicted are: (i) four disulfide bonds are predicted to be formed between Cys3 and Cys15, Cys14 and Cys285, Cys34 and Cys120 and Cys249 and Cys317; (ii) a glycosylation site, Asn257, was located on the surface; (iii) Glu40 was predicted to form a salt bridge with Arg43 on the distal side of the heme and was considered as a possible origin for the pH dependence of compound I formation; and (iv) two candidate substrate binding sites with a cluster of surface aromatic residues and flexible backbones were found in the refined model, consistent with the nature of known substrates of LiP. Based on these predicted structural features of the model, further theoretical and experimental studies are proposed to continue to elucidate the structure and function of LiP.
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PMID:Homology modeling of a heme protein, lignin peroxidase, from the crystal structure of cytochrome c peroxidase. 133 1

There is evidence to suggest that elevated levels of iodide in the diet are associated with autoimmune thyroid disease (ATD) in susceptible individuals, and that autoimmune thyroiditis (Hashimoto's disease) is less common in susceptible individuals who live in regions with dietary iodine deficiency. There are epidemiologic studies in endemic goiter areas that report an increase in ATD, particularly thyroiditis, after the therapeutic administration of iodized salt, bread and oil. Lymphocytic infiltration of the thyroid is rarely found in patients from severe endemic goiter regions, yet there is a reversal of this observation after dietary iodine supplementation. Thyroid antibodies, both thyroglobulin (TgAb) and peroxidase (TpAb) or microsomal, were not detected in serum from patients with endemic goiter, but became positive in 43% of subjects three and six months after therapy with iodized oil, and there developed transient hyperthyroidism. Similarly, the addition of iodine to the diet or the administration of iodine-containing medications increases the frequency of ATD and the severity of existing autoimmune thyroiditis. Furthermore, autoimmune thyroiditis has been induced by the administration of excess iodide to strains of chickens and rats that are genetically predetermined to develop the disease. We are beginning to understand the pathogenesis of ATD. In hyperthyroidism the evidence clearly supports the hypothesis that TSH receptor antibodies (TRAb) stimulate the TSH receptor to induce excessive and sustained secretion of thyroid hormones. Cellmediated immune mechanisms, such as antibody dependent cellmediated cytotoxicity (ADCC), initiate the lymphocytic infiltration and thyrocytotoxicity in autoimmune thyroiditis. The mechanisms that initiate the development of the abnormal immune response and the relationship of ATD with excess iodide are poorly understood. There is evidence that an increase in the iodination of thyroglobulin (Tg) enhances its immunogenicity. The results of clinical and experimental studies support the requirement of a genetic predisposition to the development of ATD that may be precipitated by exposure to certain environmental factors. Another mechanism supported by experimental data is the direct toxic effect of excess iodide on iodide-deficient thyroid glands. High concentrations of iodide after oxidation to iodine causes epithelial necrosis and inflammation associated with lipofuscin accumulation suggestive of toxicity mediated by lipid peroxidation from excessive amounts of free radicals. The epithelial damage would initiate inflammatory and immune responses. Although these mechanisms would relate to the onset of autoimmune thyroiditis on exposure to excessive amounts of iodide, the relationship of iodide intake and autoimmune hyperthyroidism is less clear.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The relationship between autoimmune thyroid disease and iodine intake: a review. 134 85


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