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 14,000-dalton polypeptide was previously reported to be the principal protein target of the carcinogen N-2-fluorenylacetamide (2-acetylaminofluorene) in liver cytosol at the start of hepatocarcinogenesis in rats. The 14,000-dalton polypeptide was purified to homogeneity according to gel electrophoreses in both NaDodSO4-containing medium and acetic acid/urea and also by immunogenicity. An immunologically related form of the cytosolic target polypeptide has now been found to be present in the nuclei of normal rat liver as a 17,500-dalton polypeptide that is firmly and ionically bound to chromatin. Serial salt extractions of isolated liver nuclei or chromatin at 0.15 and 0.35 ionic strengths fail to dissolve the bound polypeptide, according to electrophoretic transfer immunoblot analyses. Most of the 17,500-dalton polypeptide is extracted at 0.65 ionic strength, the remainder at 1.2, and none at 2.0, nor thereafter in 8 M urea. In addition, short-term digestion of purified liver nuclei with micrococcal nuclease solubilizes the 17,500-dalton polypeptide. All three protocols also solubilize low levels of intermediate 17,500- to 14,000-dalton species, the latter size being the same as that of the cytosolic protein target of the carcinogen. The presence of protease inhibitors during the isolations and extractions of the nuclei and chromatin reduces the amounts of these smaller polypeptides. In normal rat liver only nuclei and cytoplasm of hepatocytes contain reactive antigen according to peroxidase-antiperoxidase immunohistochemistry, staining most intensely perilobularly, less in the lobular midzone, and least centrilobularly. The nuclei of the perilobular hepatocytes constitute the strongest staining compartment within all of normal liver. Of 22 nonhepatic tissues of normal rats, 16 contain relatively few cells with immunoreactive cytoplasm. Nonhepatic nuclear antigen is present only in villar crest cells of duodenum (which are normally exposed to liver bile), also having cytoplasmic antigen as well. Five kinds of evidence appear to connect the chromatin-bound 17,500-dalton polypeptide of normal liver nuclei to the cytosolic 14,000-dalton polypeptide that is the principal target of the carcinogen early during hepatocarcinogenesis in rats. The present findings indicate a direct connection between a chromosomal protein and the immediate principal cytosolic protein target of a carcinogen.
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PMID:Normal liver chromatin contains a firmly bound and larger protein related to the principal cytosolic target polypeptide of a hepatic carcinogen. 658 89

During the oxidation of indole-3-acetic acid catalyzed by peroxidase, the relative amounts of the products closely depends on the enzyme/substrate ratio. In the absence of cofactors, high enzyme/substrate ratio induces a rise in the level of indole-3-aldehyde and indole-3-methanol, and a drop in that of oxindoles. 2,4-dichlorophenol, although a very efficient cofactor, promotes inhibition of the oxidation after a few minutes, presumably through the formation of a phenol-derivative inhibitor. 2-4-dichlorophenol also inhibits the production of oxindoles at all stages. Both inhibitory effects are abolished by a low concentration of enzyme. Mn2+, itself a weak inhibitor, synergizes the catalytic effect of 2,4-dichlorophenol, perhaps by preventing the formation of the inhibitor. The results are discussed against more widely accepted mechanisms of indole-3-acetic acid oxidation.
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PMID:Effects of enzyme/substrate ratio and of cofactors on the oxidation products of indole-3-acetic acid catalyzed by peroxidase. 662 7

The advantages and disadvantages of previous methods for the routine estimations of serum mono and diamine oxidase are reviewed. 4-hydroxy-3-methoxy phenyl acetic acid reacts wtih hydrogen peroxide and peroxidase to form an intensely fluorescent substance, and a simple method using this reaction as a basis for the estimation is described. The results are tabulated and discussed.
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PMID:A simple routine method for mono and diamine oxidase estimation in human serum. 678 89

A number of fixatives were tested to determine their suitability for use with the unlabelled antibody peroxidase-antiperoxidase (PAP) method for demonstrating immunoglobulin in paraffin sections of tonsil and trephine samples of bone marrow. It was found that tonsil fixed in 'isotonic' solutions of formaldehyde reacted with the PAP method only after the sections had been trypsinised. Several other fixatives, including Bouin's fluid, Carnoy's fluid, and solutions containing mercuric chloride, gave tissues which reacted without trypsinisation of sections, and particularly good results were obtained with formol saline to which acetic acid (2-10%) had been added. A combination of acetic acid (10%)-formol saline and formol sublimate also gave excellent results with bone marrow. The influence on the PAP method of a number of steps in the processing of tissues and sections was also examined.
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PMID:Effects of fixation and processing on immunohistochemical demonstration of immunoglobulin in paraffin sections of tonsil and bone marrow. 700 58

The influence of the tissue preparation on the immunohistochemical demonstration of alpha-1-antitrypsin (AAT) in liver tissue was evaluated using autopsy and biopsy material with and without AAT globules. On comparing frozen sections of unfixed material with paraffin sections of formalin fixed material a slightly better preservation of the immunoreactivity of AAT was observed in frozen sections. On comparing different fixatives, fixation in 10% neutral buffered formalin. Lillie's AAF or 96% ethanol/1% acetic acid caused a clearly better preservation of demonstrable AAT than fixation in Clarke's or Bouin's fixatives. The fixation time had only minor influence when using fixation times within a week. Extremely long fixation for several months caused, however, a clear reduction in demonstrable AAT. Pretreatment with proteolytic enzymes of deparaffinized sections of formalin fixed tissue caused an increase in demonstrable AAT, especially in tissues fixed for extremely long periods of time. On comparing three different immunohistochemical techniques: indirect immunoperoxidase, peroxidase/anti-peroxidase (PAP), and indirect immunofluorescnece, no convicting difference in sensitivity was observed between the three techniques. It is concluded that for the immunohistochemical demonstration of AAT in liver tissue the employment of indirect immunoperoxidase staining on formalin fixed, paraffin embedded material is recommendable as it combines a sensitive staining technique with a satisfactory preservation of immunoreactivity and tissue morphology.
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PMID:Immunohistochemical demonstration of alpha-1-antitrypsin in liver tissue. A methodological investigation. 700 96

[U-14C]Tyrosine-labeled noniodinated hog thyroglobulin was iodinated enzymatically and nonenzymatically (iodine, iodide-chloramine-T, pH 7.4, or iodine monochloride, pH 8.1). This led to similar levels of iodine incorporation as well as of thyroid hormone synthesis. Iodine monochloride at pH 5.5 formed "hormonogenic" iodotyrosine residues, but no hormone residues. The latter were formed when the iodinated thyroglobulin was brought to pH 8.5 and then treated with horseradish peroxidase and glucose-glucose oxidase in the absence of iodide and iodine monochloride. Enzymatic hydrolysates contained labeled hormone and pyruvic acid; acid hydrolysates labeled thyronine and acetic acid. (Treatment with acid converts hormone to thyronine and pyruvic to acetic acid.) After borohydride treatment, labeled alanine was present instead of pyruvic or acetic acid. The pyruvic acid/hormone, acetic acid/thyronine, alanine/hormone, and alanine/thyronine molar ratios always were 1, independently of the method of iodination. The "coupling reaction" consists of an oxidation step and nonoxidative coupling and decomposition steps. The oxidation step may be either enzymatic or nonenzymatic. The decomposition step always leads to 1 dehydroalanine residue for each hormone residue synthesized. (Dehydroalanine residues appear in the various hydrolysates as acetic acid, pyruvic acid, and alanine, respectively.) Since proper alignment of 2 iodotyrosine residues is a prerequisite for coupling, a model is proposed according to which oxidation of hormonogenic iodotyrosine residues leads to a charge transfer complex which is the same zwitterion-biradical resonance hybrid no matter whether it resulted from a free radical (enzymatic) or an ionic (nonenzymatic) oxidation.
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PMID:Thyroid hormone synthesis in thyroglobulin. The mechanism of the coupling reaction. 702 57

The indirect, labeled antibody and peroxidase-antiperoxidase complex (PAP) methods were studied to determine their sensitivity in detecting carcinoembryonic antigen (CEA) in conventionally processed specimens of morphologically normal human colon mucosa. CEA-positive staining was demonstrated in 13 of 19 specimens reacted with the PAP method, whereas only 4 of these specimens stained positive with the labeled antibody procedure. Detection of CEA with either technique was unrelated to normal mucosa content of antigen as determined by radioimmunoassay. Tissue fixation in 95% ethanol 1% acetic acid (EA) resulted in an enhanced and defined cytoplasmic staining of the normal colon cell lining the mucosal surface and upper levels of the glandular crypts. Cytoplasmic localization in Formalin-fixed specimens was absent or markedly reduced. Colon goblet cells and the small intestinal epithelium were CEA-negative in both Formalin- and EA-fixed specimens. These results show that the PAP immunoperoxidase method is more sensitive than the indirect, labeled antibody procedure in detecting CEA in morphologically normal colon mucosa. Furthermore, staining of tissues fixed in EA demonstrated that CEA is a product of the columnar epithelial cell and is not associated with goblet cells.
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PMID:Immunoperoxidase localization of carcinoembryonic antigen in normal human intestinal mucosa. 702 95

Conditions were sought to increase the yield of HCN from L-histidine incubated with L-amino acid oxidase (L-amino acid:oxygen oxidoreductase (deaminating), EC 1.4.3.2) from snake venom, and horseradish peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7). Small amounts of histidine and high buffer concentrations favored high HCN yields, which reached a maximum of 72%. Imidazole 4-aldehyde and imidazole 4-carboxylic acid were identified among the reaction products, together with CO2, NH3, H2O2 and imidazole acetic acid. The CO2 formed was equal to the histidine oxidized, and to the sum of NH3 plus HCN formed. The production of HCN was associated with an increased O2 uptake, which was established from the beginning of the reaction, with no apparent lag and ranged from 1.2 to 1.6 mumol extra O2 taken up/mumol HCN formed. The system was inhibited by catalase, but added superoxide dismutase caused a small stimulation of both HCN production and O2 consumption, and a larger stimulation of H2O2 accumulation. Added hydroxylamine was cooxidized to nitrite in an amount equimolar with the HCN formed. This nitrite formation was inhibited by superoxide dismutase. The facts could be interpreted in terms of superoxide anion formation during the HCN-producing reaction. cytochrome c, heme, or ferricyanide could be substituted for peroxidase, but were less effective. The initial rates of HCN formation from phenylalanine, tyrosine and tryptophan were higher, but the eventual yields of HCN from these amino acids were lower than those from histidine.
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PMID:The formation of hydrogen cyanide from histidine in the presence of amino acid oxidase and peroxidase. 735 Sep 10

A verdohemoprotein was formed from Compound I of horseradish peroxidase C upon the addition of about 2 molar equivalents of m-nitroperoxybenzoic acid (mNPBA) or hydroperoxide formed from indole-3-acetic acid during its catalytic oxidation. The formation of the verdohemoprotein occurred via two intermediates which have an absorbance peak at 965 or 940 nm. Carbon monoxide was evolved in the reaction from the 940 compound to the verdohemoprotein. From the kinetic and titration data, the following reaction sequence was proposed. (Formula: see text). The 940 compound could be reduced by dithionite and ascorbate to the ferrous and the ferric enzyme, respectively. The enzyme species that reacted with mNPBA to form the 965 and the 940 compounds was concluded to be Compound I but neither Compound II nor oxyperoxidase (Compound III).
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PMID:The conversion of horseradish peroxidase C to a verdohemoprotein by a hydroperoxide derived enzymatically from indole-3-acetic acid and by m-nitroperoxybenzoic acid. 735 79

The peroxidase associated with prostaglandin cyclooxygenase in ram seminal vesicle microsomes will utilize a wide variety of hydroperoxides and reducing substrates. One such reducing substrate, sulindac sulfide (cis-5-fluoro-2-methyl-1-[p-(methylthio)benzylidenyl]indene-3-acetic acid), inhibits the oxygenase, stimulates the peroxidase, and is oxidized to its analogous sulfoxide by the peroxidase. The peroxidase-catalyzed transfer of oxygen atoms from 15-hydroperoxyprostaglandin E2 (15-HPE2) to sulindac sulfide was examined using [18O]15-HPE2 which was prepared enzymatically and analyzed mass spectrometrically. The sulfoxide resulting from sulindac sulfide oxidation was also analyzed mass spectrometrically and found to possess an oxygen atom arising exclusively from the 15-HPE2. Since sulindac sulfide inhibits the oxygenase activity of this enzyme (ID50 approximately equal to 0.2 microM), it seemed possible that the oxygen atom was transferred while the sulfide was bound to this site. However, indomethacin, an inhibitor of the oxygenase with no effect on the peroxidase, did not alter the stoichiometry of sulindac sulfide oxidation, precluding this possibility. These findings are discussed in the context of identifying the nature of the actual oxidant and distinguishing between the oxidation mechanisms of various peroxidases and between sulindac sulfide and other reducing substrates for these enzymes.
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PMID:Mechanism of oxygen transfer by prostaglandin hydroperoxidase. 735 13


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