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Differences in peroxidase localization of rabbit peritoneal macrophages after surface adherence.

Unlike resident peritoneal macrophages, which contain peroxidase in the rough endoplasmic reticulum (RER) and perinuclear cisternae (PN), macrophages elicited into the rabbit peritoneal cavity by various stimulants lack the enzyme. Since we had previously found that such peroxidase reactivity rapidly appears in the RER and PN of blood monocytes after surface adherence in vitro, we wondered whether the enzyme could be similarly produced in elicited macrophages by adherence. Cells from peritoneal exudates (96 hours after endotoxin injection) were harvested, suspended in culture medium, and allowed to adhere to fibrin-coated or plastic surfaces. Following culture for various intervals, they were fixed, incubated for peroxidase, and examined by electron microscopy. We observed that these elicited cells, which initially contained no cytochemically detectable peroxidase, acquired peroxidatic activity in the RER and PN within 2 hours after adherence in culture. Thus macrophages, like blood monocytes, may rapidly acquire peroxidase reactivity as a consequence of plasma membrane: external surface interaction. In view of this finding, it would seem unwise to use peroxidase localization as the basis for advocating the existence of two separate lines of peritoneal macrophages, as has been proposed by previous investigators.

Animals↗

[Improved methods for the cytochemical demonstration of platelet peroxidase (author's transl)].

The variability of results to demonstrate the peroxidase of platelets has been attributed to an inhibition of the enzyme by glutaraldehyde. In order to eliminate this difficulty, two new methods have been employed prior to incubation in the diaminobenzidine medium: 1. Fixation was omitted. 2. Fixation was performed in a mixture of tannic acid-formaldehyde glutaraldehyde. With these two procedures, intense and reproducible peroxidase staining of human platelets and chicken thrombocytes was obtained. Only when the fixation procedure was omitted could the peroxidase of rat platelets be demonstrated histochemically. The importance of the detection the peroxidase as a marker enzyme of the megakaryocyte cell line and the relationships of this peroxidase with those of leukocyte peroxidases are discussed.

3,3'-Diaminobenzidine↗

Effect of fosetyl-A1 on peroxidase from grapevine (Vitis vinifera) cells.

Grapevine (Vitis vinifera cv. Monastrell) suspension cell cultures were treated with fosetyl-A1, a widely used systemic fungicide for grapevine diseases caused by oomycetes, and examined at the electron microscope level for peroxidase cytochemistry. The results showed that treatment with fosetyl-A1 provokes an activation of both vacuolar sap and tonoplast-located peroxidase, already described as due to the basic peroxidase isoenzyme, B5, which was previously characterized as a constitutive marker of disease resistance against Plasmopara viticola in axillary bud cultures of Vitis spp. This activation of peroxidase isoenzyme B5, as seen at the electron microscope level, was confirmed by cytophotometric methods, but is in contrast with the unchanged enzyme level determined by biochemical methods. These results suggest a metabolic activation of peroxidase isoenzyme B5 as a consequence of fosetyl-A1 treatment, probably due to an acidification of the vacuole. This response was accompanied by the appearance of myelin-like structures inside the cytoplasm and osmiophylic-bodies inside the mitochondria. However, the latter structural changes cannot easily be related to the above described specific peroxidase response.

Biotransformation↗

Sequences in the 3'-untranslated region of the human cellular glutathione peroxidase gene are necessary and sufficient for selenocysteine incorporation at the UGA codon.

Glutathione peroxidase (EC 1.11.1.9) is one of a unique group of prokaryotic and eukaryotic enzymes that contain the unusual amino acid selenocysteine. The genes for these selenoproteins encode for the atypical amino acid at a TGA codon (UGA in the mRNA transcripts), which normally functions as a termination signal. The present studies analyzed the functional importance of sequences in the coding and 3'-untranslated regions of transcripts of the primary human cellular glutathione peroxidase gene (GPX1) to the insertion of selenocysteine at this UGA codon. Deletions in potential stem-loop or hairpin structures in the coding region did not substantially diminish incorporation of selenocysteine into glutathione peroxidase transiently expressed by the pCMV4 vector in COS-1 cells. However, selenocysteine insertion was completely abolished by deletion of four-nucleotide sequences in the 3'-untranslated region from within a conserved "selenocysteine insertion sequence" motif also found in the 3'-untranslated region of mammalian genes for other selenoproteins. Moreover, in constructs fusing the glutathione peroxidase 3'-untranslated region to the coding region of rab5b (an unrelated protein normally without any selenium moiety), the glutathione peroxidase 3'-untranslated region was sufficient to direct the translation of an opal (UGA) mutation as selenocysteine. Thus, our data directly demonstrate the importance of the selenocysteine insertion motif in the glutathione peroxidase gene and specifically show that sequence elements in the 3'-untranslated region are both necessary and sufficient for translational insertion of selenocysteine at a UGA codon in eukaryotic mRNA.

Animals↗

Cytochemical localization of endogenous peroxidase activity in renal medullary collecting tubules and papillary mucosa of the rat.

Endogenous peroxidase activity, as demonstrated by the technique of Graham and Karnovsky (Graham RC Jr, Karnovsky MJ: J Histochem Cytochem 14:291, 1966), was identified in medullary collecting tubule cells and in the cells of renal papillary mucosa of the rat. Peroxidase reactive sites were observed in the perinuclear cisterna, endoplasmic reticulum, and cytoplasmic vesicles of such cells. The specificity of the peroxidase reaction was verified by means of chemical inhibitors (NaN3, KCN, aminotriazole), denaturation of the enzyme by heat, exclusion or prior oxidation of substrate (diamino-benzidine), and high concentration of H2O2. Prolonged fixation (glutaraldehyde) improved cellular detail but diminished or abolished the peroxidase staining. When exogenous H2O2 was excluded from the incubating medium, a positive reaction was obtained suggesting that H2O2 can be endogenously generated. This observation was confirmed by degradation of tissue-formed H2O2 with beef liver catalase and by blocking endogenous generation of H2O2 with sodium pyruvate. These studies indicate that the reaction product is the result of an enzymatic reaction and that the enzyme is most likely a peroxidase. A similar staining reaction was not observed in other tubule segments, including cortical collecting tubules. The significance of this peroxidase activity is discussed in relation to the cellular localization and biosynthesis of renal medullary prostaglandins.

Animals↗

An investigation of the metabolism of N-nitrosodimethylamine and N-nitrosomethylaniline by horseradish peroxidase in vitro.

The demethylation of carcinogenic N-nitrosodimethylamine (NDMA) and N-nitrosomethylaniline (NMA) is catalyzed by horseradish peroxidase in the presence of hydrogen peroxide. NMA is a better substrate for peroxidase than NDMA. The Km values are 0.74 and 3.12 mmol/l for NMA and NDMA, respectively. The oxidation of NDMA and NMA is inhibited by radical trapping agents (nitrosobenzene, glutathione, ascorbate, NADH). This indicates the radical mechanism for the peroxidase-mediated oxidation of both N-nitrosamines. The in vitro metabolism of NMA using peroxidase was investigated in detail. Beside formaldehyde, the metabolites formed from NMA by peroxidase include aniline, p-aminophenol and phenol. Phenol formation presumably arose from N-demethylation of NMA via a benzenediazonium ion (BDI) intermediate while aniline and p-aminophenol from denitrosation of this carcinogen. The results are discussed from the point of view of the role of peroxidases in the metabolism of N-nitrosamines.

Dimethylnitrosamine↗

Role of the apoprotein in the catalytic peroxidase-like function of ferritin.

The thermal inactivation of horse spleen ferritin was studied over a range of temperatures (36-52 degrees C) in 0.1 M acetate buffer (pH 4.2) as a decrease of its peroxidase activity during tetramethylbenzidine (TMB) oxidation by hydrogen peroxide. The activation energy of this process was 163.3 kJ/mole. Thermodynamic activation parameters for the loss of peroxidase activity of ferritin were calculated. The influence of various detergents on ferritin-dependent oxidation of TMB, ortho-tolidine, and ortho-phenylenediamine (PDA) by hydrogen peroxide was studied in 0.1 M phosphate buffer (pH 6.0) at 20 degrees C. Relatively high concentrations of charged detergents (SDS and cetyltrimethylammonium bromide) decreased the peroxidase activity of ferritin with all three amines, whereas moderate concentrations of the nonionic detergent Triton X-100 did not influence oxidation of these substrates. Increase of dimethylformamide concentration in 0.02 M acetate buffer (pH 4.2) from 5 to 40% strongly decreased the rate of TMB and PDA oxidation by hydrogen peroxide or cumene hydroperoxide. Decrease in the activity of thermally inactivated ferritin with TMB as substrate, reduction of alpha-helical content of the protein at 40-50 degrees C, an inactivating effect of charged surfactants and organic co-solvent on the peroxidase activity of ferritin indicate a very important role of the apoprotein in peroxidase function. A possible mechanism of apoferritin participation in peroxidase catalysis is discussed.

Animals↗

Immunohistochemical assessment of peroxidase-like immunoreactivity in the thyroid gland and its correlation with biochemical assay.

BACKGROUND: Peroxidase content has been recently evaluated in normal thyroid and in different thyroid disorders by biochemical, histochemical, ultrastructural and immunocytochemical methods. Nevertheless immunocytochemical detection of thyroid peroxidase in thyroid samples conventionally processed for histology has never been done using a commercially available antibody, neither its correlation with the biochemical activity on adjacent samples. METHODS: In this study we have analyzed normal thyroid tissue (3 patients), follicular adenoma (2 patients) and multinodular goiter (2 patients) conventionally processed for histology and stained by immunocytochemistry (Avidin Biotin System) using a polyclonal (rabbit) antibody for horseradish peroxidase (Serotec). Biochemical assay was performed on adjacent samples according to Hosoya method. RESULTS: Normal thyroid showed peroxidase immunoreactivity in the majority of follicular cells; neoplastic cells of adenomas were variably stained. Biochemical assay showed positive correlation with ICC ranging from 20.4 micrograms/mg/prot a in multinodular goiter to 42.12 in normal thyroid, up to 122 of follicular adenoma. CONCLUSIONS: Peroxidase content in the thyroid gland may be of clinical interest in several thyroid diseases, and in this study we have demonstrated that thyroid peroxidase can be detected by ICC in routinely processed thyroid samples using a commercially available antibody.

Adenoma↗

Molecular cloning and characterization of a new basic peroxidase cDNA from soybean hypocotyls infected with Phytophthora sojae f.sp. glycines.

Differential display techniques were used to isolate cDNA clones corresponding to genes which were expressed in soybean hypocotyls by Phytophthora sojae f.sp. glycines infection. With a partial cDNA clone C20CI4 from the differential display PCR as a probe, a new basic peroxidase cDNA clone, designated GMIPER1, was isolated from a cDNA library of soybean hypocotyls infected with P. sojae f.sp. glycines. Sequence analysis revealed that the peroxidase clone encodes a mature protein of 35,813 Da with a putative signal peptide of 27 amino acids in its N-terminus. The amino acid sequence of the soybean peroxidase GMIPER1 is between 54-75% identical to other plant peroxidases including a soybean seed coat peroxidase. Southern blot analysis indicated that multiple copies of sequences related to GMIPER1 exist in the soybean genome. The mRNAs corresponding to the GMIPER1 cDNA accumulated predominantly in the soybean hypocotyls infected with the incompatible race of P. sojae f.sp. glycines, but were expressed at low levels in the compatible interaction. Soybean GMIPER1 mRNAs were not expressed in hypocotyls, leaves, stems, and roots of soybean seedlings. However, treatments with ethephon, salicylic acid or methyl jasmonate induced the accumulation of the GMIPER1 mRNAs in the different organs of soybean. These results suggest that the GMIPER1 gene encoding a putative pathogen-induced peroxidase may play an important role in induced resistance of soybean to P. sojae f.sp. glycines and in response to various external stresses.

Acetates↗

A new, one-step assay on whole cell suspensions for peroxidase secretion by human neutrophils and eosinophils.

The degranulation of neutrophils and eosinophils is frequently monitored by assaying myeloperoxidase (MPO) and eosinophil peroxidase (EPO) activity in the cell-free supernatant of degranulating cells, after removal of the cells by centrifugation. This procedure leads to underestimation of the extent of degranulation, since both peroxidases tend to stick to cell surfaces, to test tube walls, and to particulate stimuli used to elicit degranulation, because of their highly cationic nature. In this paper we describe a method for assaying MPO and EPO secretion in whole cell suspensions that avoids separation of the cells from the incubation medium. The least toxic and thus safest among the sensitive peroxidase substrates, 3,3',5,5'-tetramethylbenzidine (TMB), was employed for peroxidase assay. The method we describe here is applied to the detection of peroxidase release by neutrophil and eosinophil cell suspensions incubated in either polypropylene test tubes or flat-bottomed microtiter plate wells. Because of the omission of the centrifugation step, the TMB method offers two major advantages over the currently used techniques: (1) higher estimates of degranulation, which permits the use of a smaller number of cells (in the microassay version, 150,000 neutrophils and 50,000 eosinophils) and smaller amounts of the secretagogues, and (2) rapidity, since the degranulation assay can be performed immediately on completion of the cell incubation with the secretagogue.

Calcimycin↗

Resonance Raman study on yeast cytochrome c peroxidase. Effect of coordination and axial ligands.

Resonance Raman spectra are reported for native ferric cytochrome c peroxidase, its cyanide and fluoride compounds, those of the ferrous enzyme and its cyanide and carbonyl compounds, and the spectrum of the hydrogen peroxide compound, compound I. Band frequencies of ferric horseradish peroxidase isoenzyme C2 and its derivatives are also given. Comparison of the frequencies of the bands around 1400, 1500, 1560-1580, and 1610-1640 cm-1 with those of other hemoproteins and heme model compounds showed that in ferric highspin compounds in particular the bands are not only spin and oxidation sensitive, as has previously been reported, but that they also reflect the coordination of the heme iron. It is suggested that ferric cytochrome c peroxidase and horseradish peroxidase are pentacoordinated. In the hexacoordinated fluoride, cyanide and carbon monoxide derivatives the bands reflect the spin state and the out-of-plane position of the heme iron. The spectrum of cytochrome c peroxidase compound I supports previous studies that suggest that it has a lowspin heme iron in the Fe(IV) oxidation state.

Binding Sites↗

Ascorbate is the natural substrate for plant peroxidases.

Ascorbate-dependent detoxification of hydrogen peroxide by guaiacol-type peroxidases is increased considerably in the presence of 3,4-dihydroxyphenolic compounds, suggesting that ascorbate is the natural substrate for many types of peroxidase in situ and not just the ascorbate-specific peroxidases. The ascorbate-dependent destruction of hydrogen peroxide in the more acidic cellular compartments such as the vacuole may be an important function of such non-specific peroxidases. The stress-induced production of phenolic compounds would render the guaiacol peroxidases in other less acidic-cellular sites effective as ascorbate-dependent H2O2-detoxifying enzymes.

Antibodies↗

Novel sites of cytosolic glutathione peroxidase expression in colon.

Glutathione peroxidases (Gpx) are important moderators of oxidative stress that is implicated in the pathogenesis of numerous diseases including colon cancer. Previous studies report limited examinations of cytosolic glutathione peroxidase location of expression in colon tissue. This study reports evidence of both common sites of Gpx1 and Gpx2 expression in rat colon and sites that are exclusive to each isoform. Semi-quantitative PCR performed previously demonstrated RNA expression of Gpx1 and Gpx2 in proximal, transverse and distal colon. Mapping the distribution throughout the entire colon has revealed specific, novel sites of glutathione peroxidase expression in colon lymphatic tissue. In situ hybridisation and immunohistochemistry confirmed micro-anatomical location of Gpx1 within lymphatic tissue and the lamina propria, sub-mucosa, muscularis and serosa, but not the lumenal epithelium. In situ hybridisation and immunohistochemistry were consistent with reports of microanatomical location of Gpx2 in the lumenal epithelium. Novel sites of Gpx2 expression were also observed in lymphatic tissue. Immunolocalisation in the vicinity of aberrant crypt foci was also examined to further investigate the link between glutathione peroxidases and colon cancer. This did not reveal significant abnormalities, nor did measurement of cytosolic glutathione peroxidase activity or gene expression in colon tissue from rats treated with the colontropic chemical, 1,2-dimethylhydrazine. These results support the potential for Gpx1 and Gpx2 redundancy in lymphatic tissue, but not in epithelial cells of the colon crypt or in the lamina propria, sub-mucosa, muscularis or serosa.

Animals↗

Role of electrostatics and salt bridges in stabilizing the compound I radical in ascorbate peroxidase.

Cytochrome c (CcP) and ascorbate peroxidase (APX) are heme peroxidases which have very similar active site structures yet differ substantially in the properties of compound I, the intermediate formed upon reaction with peroxides. Although both peroxidases have a tryptophan in the proximal heme pocket, Trp191 in CcP and Trp179 in APX, only Trp191 in CcP forms a stable cation radical while APX forms the more traditional porphyrin pi-cation radical. Previous work [Barrows, T. P., et al. (2004)Biochemistry 43, 8826-8834] has shown that converting three methionine residues in the cytochrome c peroxidase (CcP) proximal heme pocket to the corresponding residues in APX dramatically decreased the stability of the Trp191 radical in CcP compound I. On the basis of these results, we reasoned that replacing the analogous residues at positions 160, 203, and 204 in APX with methionine should stabilize a Trp179 radical in APX compound I. Steady- and transient-state kinetics of this mutant (designated APX3M) show a significant destabilization of the native porphyrin pi-radical, while electron paramagnetic resonance (EPR) studies show an increase in the intensity of the signal at g = 2.006 with characteristics consistent with formation of a Trp radical. This hypothesis was tested by replacing Trp179 with Phe in the APX3M background. The EPR spectrum of this mutant was very similar to that of the CcP W191G mutant which is known to form a tyrosine radical. Previously published theoretical studies [Guallar, V., et al. (2003) Proc. Natl. Acad. Sci. U.S.A. 100, 6998-7002] suggest that electrostatic shielding of the heme propionates also plays a role in the stability of the porphyrin radical. Arg172 in APX hydrogen bonds with one of the heme propionates. Replacing Arg172 with an asparagine residue in the APX3M background generates a mutant which no longer forms the full complement of the compound I porphyrin pi-radical. These results suggest that the electrostatics of the proximal pocket and the shielding of propionate groups by salt bridges are critical factors controlling the location of a stable compound I radical in heme peroxidases.

Arginine↗

Redox properties of the couple compound I/native enzyme of myeloperoxidase and eosinophil peroxidase.

The standard reduction potential of the redox couple compound I/native enzyme has been determined for human myeloperoxidase (MPO) and eosinophil peroxidase (EPO) at pH 7.0 and 25 degrees C. This was achieved by rapid mixing of peroxidases with either hydrogen peroxide or hypochlorous acid and measuring spectrophotometrically concentrations of the reacting species and products at equilibrium. By using hydrogen peroxide, the standard reduction potential at pH 7.0 and 25 degrees C was 1.16 +/- 0.01 V for MPO and 1.10 +/- 0.01 V for EPO, independently of the concentration of hydrogen peroxide and peroxidases. In the case of hypochlorous acid, standard reduction potentials were dependent on the hypochlorous acid concentration used. They ranged from 1.16 V at low hypochlorous acid to 1.09 V at higher hypochlorous acid for MPO and from 1.10 V to 1.03 V for EPO. Thus, consistent results for the standard reduction potentials of redox couple compound I/native enzyme of both peroxidases were obtained with all hydrogen peroxide and at low hypochlorous acid concentrations: possible reasons for the deviation at higher concentrations of hypochlorous acid are discussed. They include instability of hypochlorous acid, reactions of hypochlorous acid with different amino-acid side chains in peroxidases as well as the appearance of a compound I-chloride complex.

Eosinophil Peroxidase↗

Hereditary eosinophil peroxidase deficiency: immunochemical and spectroscopic studies and evidence for a compound heterozygosity of the defect.

Hereditary eosinophil peroxidase (EPO; EC 1.11.1.7) deficiency is a rare abnormality of eosinophil granulocytes characterized by decreased or absent peroxidase activity and decreased volume of the granule matrix. The molecular basis of the defect is not known. We report here its molecular characterization in an EPO-deficient subject and his family members. The EPO-deficient eosinophils contained EPO-related material as determined immunochemically using either monoclonal or polyclonal anti-EPO antibodies but had no spectroscopic evidence of EPO. Eosinophil precursors from the EPO-deficient subject contained normally sized EPO mRNA, which was reverse transcribed into the corresponding cDNA clones encompassing the whole gene. Sequencing of these clones disclosed two mutations, a G-->A transition causing a nonconservative replacement of an arginine residue with a histidine and an insertion causing a shift in the reading frame with the appearance of a premature stop codon. The two mutations were located on different chromosomes indicating a compound heterozygosity for the defect. Both the son and the daughter of the proband inherited the G-->A transition, and their eosinophils contained a peroxidase activity intermediate between that of control subjects and the proband, suggesting that the transition is a deficiency-causing mutation. Eosinophil precursors from the EPO-deficient subject were found to actively synthesize an EPO that was apparently normal in terms of cytochemical reaction for peroxidase and immunoreactivity with monoclonal and polyclonal anti-EPO antibodies, but spectroscopically abnormal. The cytochemical reaction for peroxidase tended to decrease or disappear in the eosinophil precursors of the EPO-deficient subject but not of a normal subject as differentiation went on, suggesting that the Arg-->His substitution causes the production of an unstable EPO that undergoes progressive degradation as the cells mature.

Amino Acid Sequence↗

Regulatory effects of iodide and thiocyanate on tyrosine oxidation catalyzed by thyroid peroxidase.

the effects of iodide, thiocyanate and perchlorate, three anions with the same molecular size, on the oxidation of tyrosine to 3,3'-bityrosine by several peroxidases were evaluated at pH 8.8, i.e. in conditions in which iodide is not oxidized. The following results were obtained: 1. Iodide greatly stimulates the rate of bityrosine formation in the presence of thyroid peroxidase. No effect was seen with horseradish peroxidase or lactoperoxidase. Maximal iodide effects were obtained with about 0.5 mM iodide and Km for iodide was equal to about 0.028 mM. These results suggest that thyroid peroxidase contains a simple class of regulatory binding sites for iodide. 2. SCN- mimics iodide effects; maximal stimulatory effects were seen with about 0.5 mM thiocyanate and Km for SCN- was equal to 0.1 mM. The effects of SCN- and those of iodide were not additive. These results suggest that SCN- binds to the same regulatory site as iodide but with a slightly lower affinity. No effect of SCN- was seen with horseradish peroxidase or lactoperoxidase. 3. ClO-4, another anion with the same molecular size as iodide and SCN-, had neither an effect on the oxidation of tyrosine to bityrosine nor did it prevent the stimulatory effect of iodide on this reaction. Bromide was without effect on the same reaction.

Horseradish Peroxidase↗

Indole-3-Acetic Acid Control on Acidic Oat Cell Wall Peroxidases.

Incubation of oat coleoptile segments with 40 µm indoleacetic acid (IAA) induced a decrease of 35-60% in peroxidase activity at the cell wall compartment. Treatment with IAA also produced a similar decrease in the oxidation of NADH and IAA at the cell wall. Isoelectric focusing of ionic, covalent, and intercellular wall peroxidase fractions showed that acidic isoforms (pI 4.0-5.5) were reduced preferentially by IAA treatment. Marked differences were found between acidic and basic wall isoperoxidases in relation to their efficacy in the oxidation of IAA. A peroxidase fraction containing acidic isoforms oxidized IAA with a V(max)/s(0.5) value of 2.4 x 10(-2) min(-1). g fw(-1), 4.0 times higher than that obtained for basic peroxidase isoforms (0.6 x 10(-2) min(-1). g fw(-1)). In contrast, basic isoforms were more efficient than acidic isoperoxidases in the oxidation of coniferyl alcohol or ferulic acid with H(2)O(2) (5.6 and 2.1 times, respectively). The levels of diferulate and lignin in the walls of oat coleoptile segments were not altered by treatment with IAA. The decrease in cell wall peroxidase activity by IAA was related more to reduced oxidative degradation of the hormone than to covalent cell wall cross-linking.Key Words. IAA-Auxin-Wall peroxidases-Oat-Avena sativa-Diferulic acid-Ligninhttp://link.springer-ny.com/link/service/journals/00344/bibs/18n1p25.html

Journal Article↗