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  • 1
    Electronic Resource
    Electronic Resource
    Concurrent Reduction of Iodine and Oxidation of EDTA at the Active Site of Horseradish Peroxidase: Probing the Iodine Binding Site by Optical Difference Spectroscopy and Steady State Kinetic Analysis for the Formation of Active Enzyme-I+-EDTA Ternary Complex and for Iodine Reductase Activity (1995)
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 12998-13006 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00040a010
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  • 2
    Electronic Resource
    Electronic Resource
    Melatonin protects against stress-induced gastric lesions by scavenging the hydroxyl radical (2000)
    Copenhagen : Munksgaard
    Journal of pineal research 29 (2000), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The antiulcer effect of melatonin on gastric lesions caused by restraint-cold stress or by indomethacin (IMN) was studied with the intent of determining the mechanism of action of the indole. Melatonin dose-dependently prevents both stress and IMN-induced gastric damage with around 90% inhibition at a dose of 60 mg per kg BW. When compared with already-marketed antiulcer drugs, such as ranitidine and omeprazole, melatonin was found to be more effective than ranitidine but less effective than omeprazole in preventing stress ulcer. When compared with other antioxidants, melatonin was more potent than glutathione and essentially equipotent to α-tocopherol in blocking stress-induced ulcer. As stress-induced gastric lesions are mainly caused by oxidative damage due to hydroxyl radicals (OH), the effect of melatonin in scavenging the OH generated during stress conditions, as well as in an in vitro model system, was studied. The results indicate that melatonin at the dose of 60 mg per kg BW caused an 88% reduction of endogenous OH during stress. Melatonin was also highly effective in scavenging OH generated in vitro by a Cu2+-ascorbate system. In this case, melatonin at 100 μM reduced OH by 80%. Melatonin was also found to be a more potent radical scavenger than benzoate, a known OH scavenger. The results indicate that melatonin prevents stress-induced gastric lesions by scavenging the endogenous OH. As it also protects against IMN-induced gastric damage, it probably also offers gastroprotection by maintaining endogenous prostaglandin levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-079X.2000.290303.x
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  • 3
    Electronic Resource
    Electronic Resource
    EDTA inhibits lactoperoxidase-catalyzed iodide oxidation by acting, as an electron-donor and interacting near the iodide binding site (1996)
    Springer
    Molecular and cellular biochemistry 162 (1996), S. 105-111 
    Details
    ISSN: 1573-4919
    Keywords: lactoperoxidase ; EDTA oxidation ; EDTA binding ; iodide oxidation ; EDTA as electron-donor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Ethylenediamine tetraacetate ( EDTA ) inhibits lactoperoxidase (LPO)-catalyzed rate of iodide oxidation in concentration and pH-dependent manner. A plot of log Kiapp values against various pH yields a sigmoidal curve from which an ionisable group of pKa value 6.0 could be ascertained for controlling the inhibition of catalytically active LPO by EDTA. Kinetic studies indicate that EDTA competitively inhibits iodide oxidation by acting as an electron donor. EDTA al so reduces LPO-compound-11 to the native ferric state by one-electron transfer as evidenced by the spectral shift from 428 to 412 nm. Optical difference spectroscopic studies indicate that EDTA binds to LPO with the apparent equilibrium dissociation constant (KD) of 12 ± 2 mM at pH 6.5. A plot of log KD values against various pH produces a sigmoidal curve from which an ionisable group of LPO having pka = 5.47 could be calculated, deprotonation of which favours EDTA binding. EDTA also binds to LPO-CN- complex indicating its binding site away from heme iron centre. The KD of LPO-EDTA complex is significantly increased (62 ± 5 mM) by iodide suggesting that EDTA binds close to the iodide binding site. EDTA also increases the KD value of LPO-hydroquinone complex from 62 ± 5 mM to 200 ± 21 mM indicating that EDTA and aromatic donor binding sites are also close. We suggest that EDTA inhibits iodide oxidation competitively as an electron donor by interacting at or near the iodide binding site and these sites are close to the aromatic donor binding site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227536
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  • 4
    Electronic Resource
    Electronic Resource
    Salivary peroxidases (1986)
    Springer
    Molecular and cellular biochemistry 70 (1986), S. 21-29 
    Details
    ISSN: 1573-4919
    Keywords: peroxidase ; salivary glands ; thyroid gland ; extrathyroidal tissues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Peroxidases are known to be involved in the intracellular metabolism of H2O2 coupled with various physiological functions. Apart from the thyroid gland, the enzyme has been isolated from various extrathyroidal sources of which salivary gland is one of the richest sources of the enzyme. The enzyme from bovine and goat submaxillary gland has been extensively studied in terms of their molecular, spectral, kinetic, catalytic and immunological properties and compared with the lactoperoxidase which is similar to the salivary peroxidase. The modulation of the salivary peroxidase by various factors and the probable mechanism of the modulation has been described. The enzyme has also been compared with the thyroid peroxidase as regards their physicochemical properties as well as on the immunological and functional aspects. The similarities and dissimilarities have been incorporated. The possible function of the enzyme in iodine metabolism and in bactericidal action has been discussed.[/p]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233801
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  • 5
    Electronic Resource
    Electronic Resource
    Immunological characterization of soluble peroxidases from rat tissues including preputial gland (1987)
    Springer
    Molecular and cellular biochemistry 77 (1987), S. 127-134 
    Details
    ISSN: 1573-4919
    Keywords: preputial peroxidase ; submaxillary peroxidase ; lacrimal peroxidase ; uterine fluid peroxidase ; rat soluble peroxidases ; peroxidase biosynthesis ; lactoperoxidase antiserum ; harderian gland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A highly active soluble peroxidase has been identified in the preputial gland of rats and characterized immunologically along with other soluble peroxidases of a number of rat tissues such as submaxillary gland, exorbital lacrimal gland and also of the uterine fluid of the estrogen treated rats. All these peroxidases have the native molecular weight around 73K as determined by gel filtration on Sephadex G-150. An antiserum raised against the pure bovine lactoperoxidase interacts with all these soluble peroxidases and immunoprecipitates the enzyme activity in a similar fashion when titrated against varied concentration of the antiserum. Following electrophoretic transfer to nitrocellulose by Western blotting, the antiserum crossreacts with the preputial, submaxillary and lacrimal gland protein of molecular weight around 73K and with the uterine fluid protein of molecular weight of 80K. An additional crossreacting protein of molecular weight of 80K is also evident in the lacrimal gland. All these enzyme preparations, however, contain another immunoreactive protein of molecular weight of about 64K. While 73–80K molecular weight interacting proteins may represent different forms of peroxidase, presumably with varied carbohydrate moieties, 64K molecular weight protein may be a precursor of the peroxidase which after posttranslational modification such as heme conjugation and glycosylation leads to formation of native enzyme. Rat harderian gland, unlike bovine origin, does not contain any detectable peroxidase activity. The immunoblot does not show the presence of any immunoreactive protein around 73K except the 64K molecular weight protein indicating that this gland can not synthesize the native peroxidase from this precursor probably due to some block in posttranslational modification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221921
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of stress on the antioxidant enzymes and gastric ulceration (1993)
    Springer
    Molecular and cellular biochemistry 125 (1993), S. 115-125 
    Details
    ISSN: 1573-4919
    Keywords: stress induced gastric ulcer ; gastric peroxidase ; gastric superoxide dismutase ; gastric prostaglandin synthetase ; lipid peroxidation ; reactive oxygen species ; oxidative gastric damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of cold-restraint stress on the antioxidant enzymes of the rat gastric mucosa was studied with a view to finding out their role in stress induced gastric ulceration. Histological examination revealed stress induced extensive damage of the surface epithelial cell with lesions extending upto submucosa in some cases. Stress causes time-dependent increase in histamine and pepsin content but decrease in acid content of the gastric fluid with the progress of ulceration (ulcer index) for two hours. The tissue lipid peroxidation was significantly increased as evidenced by accumulation of malondialdehyde. Since lipid peroxidation results from the generation of reactive oxygen species, stress effect was studied on some antioxidant enzymes such as superoxide dismutase, peroxidases and prostaglandin synthetase as a function of time. The time dependent increase in stress ulcer correlates well with the concomitant increase in superoxide dismutase activity and decrease in peroxidase and prostaglandin synthetase activity. This creates a favourable condition for accumulation of endogenous H2O2 and more reactive hydroxyl radical (OH·). Administration of antioxidants such as reduced glutathione or sodium benzoate prior to stress causes significant decrease in ulcer index and lipid peroxidation and protection of gastric peroxidase activity suggesting the involvement of reactive oxygen species in stress induced gastric ulceration. This is supported by thein vitro observation that OH· can also inactivate peroxidase and induce lipid peroxidation. As prostaglandin is known to offer cytoprotection, stress-induced loss of prostaglandin synthetase activity appears to aggravate the oxidative damage caused by reactive oxygen species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00936440
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  • 7
    Electronic Resource
    Electronic Resource
    Proteoliposome as the model for the study of membrane-bound enzymes and transport proteins (1983)
    Springer
    Molecular and cellular biochemistry 50 (1983), S. 3-15 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Reconstitution of membrane-bound enzymes and transport proteins with the artificial phospholipid bilayer (liposomes) is one of the most useful techniques to study the functional aspects of these proteins. Several biochemical and biophysical parameters related to the expression of the functions of these proteins can be conveniently studied in the reconstituted proteoliposomes. Methods have been described for the preparation of model membranes and emphasis has been given specially to liposomes. Methodologies for the reconstitution of biologically active proteoliposomes using varieties of membrane-bound enzymes and proteins and their assay have been presented in details. The merits and demerits of each method and the subsequent modification of the technique have been indicated. Factors controlling the orientation and functions of the enzymes and carrier proteins in the reconstituted proteoliposomes have also been described. Attempts have been made to include few examples to describe how the reconstituted model membrane is helping us to know the molecular basis of many salient features of the biomembranes. Finally, the possible application of the proteoliposomes for the study of other complex membrane phenomena has been postulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225276
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  • 8
    Electronic Resource
    Electronic Resource
    Membrane peroxidases (1988)
    Springer
    Molecular and cellular biochemistry 83 (1988), S. 105-128 
    Details
    ISSN: 1573-4919
    Keywords: extrathyroidal peroxidases ; memb\`ranebound peroxidases ; gastric peroxidase ; intestinal peroxidase ; uterine peroxidase ; eosinophil peroxidase ; mammary gland peroxidase ; ovoperoxidase ; spleen heme peroxidase ; prostaglandin endoperoxide synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary It is well known that the partial reduction of oxygen can result in the formation of highly reactive oxygen products. Hydrogen peroxide is one of these metabolites of oxygen. Peroxidases utilize this metabolite for a variety of functions. It is the purpose of this treatise to review the nature and function of various membrane peroxidases in the body.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226140
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  • 9
    Electronic Resource
    Electronic Resource
    Ecto-ATPase (1981)
    Springer
    Molecular and cellular biochemistry 37 (1981), S. 91-99 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary An ecto-adenosine triphosphatase (E.C. 3.6.1.4 ATP-phosphohydrolase) is shown to be localised on the outer surface of varieties of cell membrane. The enzyme is different from the ATPase involved in biological energy transduction and ion transport mechanism. The characteristic of the enzyme lies in having a very broad substrate specificity and is inhibited by EDTA and higher concentration of ATP. The enzyme is dependent on bivalent metal ions, Mg++ or Ca++ for its optimum activity. The enzyme is highly sensitive to SH-reagents but insensitive to inhibitors of mitochondrial ATPase or Na+−K+-ATPase. The possible functions of the enzyme in being oriented outside the cell membrane is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02354932
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