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PubMed1972

Cytochemical localization of peroxidase activity in the developing erythrocyte.

Peroxidase activity, demonstrated with diaminobenzidine as the electron donor according to the method of Graham and Karnovsky, was used as a cytochemical marker in a study of developing erythrocytes in guinea pig and rabbit bone marrow. Peroxidase activity was deposited diffusely in the cytoplasm and nuclear matrix of developing cells and was thought to represent hemoglobin, which others have shown by independent criteria to have a similar distribution. Diffuse localization was first observed in erythroblasts and at all subsequent stages of development. Another finding was the significant particulate localization of peroxidase activity apparently associated with cytoplasmic ribosomes and nuclear particles of immature erythrocytes. This activity differentiated the most primitive erythroid precursors from hemocytoblasts of other marrow cell lines, a distinction impossible by strictly morphologic criteria. Particulate peroxidase localization was identified in erythroid hemocytoblasts, erythroblasts, normoblasts and reticulocytes but not in mature erythrocytes. The nature of the particle-associated peroxidase activity was not determined with certainty. However, it could not be differentiated from the diffuse activity, thought to reflect hemoglobin, by several inhibitors and could not be attributed to erythrocyte catalase. The possibility is therefore raised that this activity represents hemoglobin, newly assembled either on or immediately adjacent to nuclear particles and cytoplasmic ribosomes.

Aniline Compounds↗
PubMed1983

Labelling of amoeboid microglial cells in the supraventricular corpus callosum following the application of horseradish peroxidase in the cerebrum and spinal cord in rats.

Following an injection of horseradish peroxidase solution into the cervical or lumbosacral segments of the spinal cords, or into the parietal cortices, of postnatal (1-10 days), developing (15-20 days) and mature (2 months and older) rats, only postnatal rats demonstrated peroxidase-positive amoeboid microglial cells in the supraventricular part of the corpus callosum. The amoeboid microglial cells were bilaterally labelled following a unilateral injection into the parietal cortex or the spinal cord. They were, however, not labelled after 15 minutes, but were definitely labelled 1 hour after the injection of the solution into the spinal cord. Also, they were not labelled when the solution was injected into the central canal or the subarachnoid space. The results suggest an ascending diffusion of the injected horseradish peroxidase in the spinal cord via the wide interstitial spaces to reach the cerebrum where it is engulfed by the amoeboid microglial cells. An enhanced activity of endogenous peroxidase was also indicated by the observation of peroxidase product in the lysosomal granules of the amoeboid microglial cells.

Animals↗
PubMed1982

Peroxidase content in cell subpopulations of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats.

Peroxidase has been investigated as a potential marker protein for the prediction of response to hormonal therapy in tumors of steroid-sensitive tissues, but the cellular origin of the enzyme has been questioned. To localize the observed peroxidase activity, in this study cell subpopulations were isolated from mammary tumors induced by 7,12-dimethylbenz(a)anthracene and from mammary tissue of virgin and lactating female rats. Cells from each of the four cell bands, regularly obtained by isopyknic velocity sedimentation after mechanical and enzymatic dispersion of these tissues, were assayed biochemically and histochemically for peroxidase activity. In addition, cells from each subpopulation were examined at both the light and electron microscopic levels. Elevated enzyme levels were observed in each of the cell subpopulations of 7,12-dimethylbenz(a)anthracene-induced tumors when these were compared with tissue in either of the physiological states assayed. In each tissue type, the levels of peroxidase increased from the lighter cell bands to the heavier cell bands. Light and electron microscopic examination revealed the highest proportion of epithelial cells in the lighter bands and an increase in granulocytes and fibroblasts in the heavier bands, suggesting a nonepithelial contribution. Histochemical examination of intact tissue revealed most peroxidase activity in the stromal compartment with limited activity in parenchymal cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

[Quantitative kinetic study of the histochemical reaction to peroxidase in salivary gland and uterine cells of golden hamsters].

The kinetics of diaminobenzidine reaction for peroxidase has been studied using cryostat sections of salivary gland and uterus of the golden hamster. It was demonstrated that the inhibition of the initial velocity of the reaction in salivary gland occurred at hydrogen peroxide concentration in the reaction medium being 5.10(-3) M or higher. On the other hand, the inhibitory action of hydrogen peroxide excess on the uterine peroxidase activity was observed at H2O2 concentrations higher than 1.10(-3) M. KM values for diaminobenzidine, determined for salivary gland and uterine peroxidases, were 2.3.10(-3) M and 3.5.10(-3) M, resp; KM values for H2O2 were 1.1.10(-4) M and 2.5.10(-5) M, resp. Kinetic difference of salivary gland and uterine peroxidases obtained in this study support the view on the organ specificity of peroxidases.

3,3'-Diaminobenzidine↗
PubMed1980

Racial differences in oestrogen receptor and peroxidase status of human breast cancer tissue.

Cytoplasmic oestradiol receptors and peroxidase from 170 tumours from patients with breast cancer were assayed. The results were analysed in terms of racial groups and menopausal status. It was found that 68% of the receptor-positive tumours were peroxidase-positive, while 59% of the receptor-negative tumours were peroxidase-positive. When results were analysed in terms of racial groups 68% of tumours from White patients were peroxidase-positive and receptor-positive, while only 48% of receptor-negative tumours in this group were peroxidase-positive. This contrasts with the finding of 57% receptor-positive/peroxidase-positive tumours as opposed to 70% receptor-negative/peroxidase-positive tumours in Black patients.

Black People↗
PubMed1994

Protein G-horseradish peroxidase based method for light-microscope immunocytochemistry. Application to the pituitary gland of the killifish, Fundulus heteroclitus.

Horseradish peroxidase-protein G conjugate was used to localize anti-human luteinizing hormone and anti-human chorionic gonadotropin primary antibodies bound to gonadotropins in paraffin and Historesin embedded sections of Fundulus heteroclitus pituitaries. The sensitivity and specificity of this method and those obtained after the avidin-biotin-peroxidase complex, the streptavidin-biotin-peroxidase complex and the peroxidase-antiperoxidase procedures were compared. The protein G-horseradish peroxidase method gave a clear immunostaining of gonadotrophic cells with virtually no background. Detection efficiency was reduced in comparison with the other techniques. As for the embedding medium, hydrophilic resin Historesin considerably enhanced the structural detail and the resolution of the immunostaining at light-microscope level.

Animals↗
PubMed1994

The thioredoxin and glutaredoxin systems are efficient electron donors to human plasma glutathione peroxidase.

Human plasma glutathione peroxidase (GSH-Px) is a distinct extracellular selenoenzyme that detoxifies hydroperoxides when used with GSH in high (mM) non-physiological concentrations. We have discovered that NADPH and human thioredoxin reductase (TR) by itself or with thioredoxin (Trx) are efficient electron donors to this human plasma peroxidase. Incubation of 0.05 microM TR with 0.25 microM GSH-Px, in a system free from GSH, resulted in reduction of t-butyl hydroperoxide. Addition of Trx, 2.5 and 5 microM, respectively, further increased the rate of the reaction. These data were obtained using an assay measuring the oxidation of NADPH. A direct assay demonstrated the formation of cumyl alcohol from cumene hydroperoxide in this GSH-independent peroxidase reaction. Incubation of 0.25 microM GSH-Px with a low concentration of GSH (10 microM), representing the upper level in plasma, plus excess glutathione reductase and NADPH did not result in any reduction of t-butyl hydroperoxide. However, after addition of 2.5 microM human glutaredoxin, a linear peroxidase reaction started. The results suggest that extracellular TR, Trx, or glutaredoxin are reductants for the selenium-dependent peroxidase rather than GSH.

Electron Transport↗
PubMed1994

Interaction between peroxidase and cyclooxygenase activities in prostaglandin-endoperoxide synthase. Interpretation of reaction kinetics.

Prostaglandin-endoperoxide synthases have two distinct enzymatic activities in the biosynthesis of prostanoids: a peroxidase and a fatty acid oxygenase. Hydroperoxides, such as the cyclooxygenase reaction product, prostaglandin G2, act both as substrates for the synthase peroxidase and as obligatory initiators of the cyclooxygenase reaction itself. A mechanistic scheme was devised to describe the interactions between the two activities of the synthase. This mechanism was based on a heme-dependent peroxidase mechanism such as that observed with horseradish peroxidase and initiation of the cyclooxygenase reaction by intramolecular reaction with a peroxidase intermediate. Rate equations derived from the mechanism were numerically integrated by an interactive computer program that consolidated the diverse phenomena to provide quantitative predictions of the reaction kinetics of the synthase. The predictions agreed well with experimental observations of the purified ovine seminal vesicle enzyme under a wide variety of conditions, including inhibition by exogenous hydroperoxide scavenger and by cyanide, stimulation by exogenous hydroperoxide, and inhibition of eicosapentaenoic acid oxygenation under conditions where arachidonic acid reacts rapidly. The detailed analyses of reaction kinetics made possible with the computer simulation provide important insights into the interactions between the two catalytic activities of the synthase in the control of prostaglandin biosynthesis.

Cyanides↗
PubMed1993

Structural and functional heterogeneity among peroxidase-negative granules in human neutrophils: identification of a distinct gelatinase-containing granule subset by combined immunocytochemistry and subcellular fractionation.

The existence of separate gelatinase granules in human neutrophils has been a matter of debate in recent years. We have demonstrated that the 135-kD form of neutrophil gelatinase is a complex of 92-kD gelatinase and a novel 25-kD protein termed neutrophil gelatinase-associated lipocalin (NGAL) that, in addition to being complexed with part of the gelatinase, is localized in free form in peroxidase-negative specific granules. Because this association was not appreciated in earlier studies, we decided to reassess the ultrastructural localization of gelatinase using specific antibodies without immunoreactivity towards NGAL. Double-labeling immunogold electron microscopy was performed on frozen thin sections of human neutrophils. Twenty-four percent of all peroxidase-negative granules were labeled with antigelatinase antibody, but not with antilactoferrin antibody. These granules are defined as gelatinase granules. Sixteen percent reacted with antilactoferrin antibody but not with antigelatinase antibody. The rest (60%) reacted with both antibodies. All granules labeling for lactoferrin are defined as specific granules. Gelatinase granules were observed as round and oval forms of considerably smaller size than specific granules, and were less electron dense. Isolated granules obtained by subcellular fractionation were also examined by immunoelectron microscopy. This demonstrated that peroxidase-negative granules comprise a continuum from the most dense granules that contain lactoferrin but no gelatinase to the lightest that contain gelatinase but no lactoferrin. Thus, gelatinase granules do exist as a subpopulation of peroxidase-negative granules and may allow for exocytosis of gelatinase during neutrophil diapedesis without substantial mobilization of other peroxidase-negative granules, ie, specific granules.

Cytoplasmic Granules↗
PubMed1993

Expression, characterization, and tissue distribution of a new cellular selenium-dependent glutathione peroxidase, GSHPx-GI.

We have characterized a new selenium-dependent glutathione peroxidase, GSHPx-GI, by expressing a GSHPx-GI cDNA isolated from human hepatoma HepG2 cells in human mammary carcinoma MCF-7 cells, which have virtually undetectable expression of either the classical cellular enzyme, GSHPx-1, or GSHPx-GI at the protein level. One of the G418-resistant clones, neo-D1, expresses the transfected GSHPx-GI cDNA. This is based on 1) the presence of an additional GSHPx-GI DNA restriction fragment detected by Southern analysis; 2) the presence of a 1.9-kilobase (kb) GSHPx-GI mRNA in addition to the 1.0-kb endogenous mRNA by Northern analysis; and 3) the appearance of a 22-kDa 75Se-labeled protein which is absent in parental MCF-7 cells revealed by SDS-polyacrylamide gel electrophoresis. GSHPx-GI expressed in neo-D1 is a tetrameric protein localized in cytosol. GSHPx-GI does not cross-react with antisera against human GSHPx-1 or human plasma glutathione peroxidase (GSHPx-P). Similar substrate specificities are found for GSHPx-1 and GSHPx-GI; they both catalyze the reduction of H2O2, tert-butyl hydroperoxide, cumene hydroperoxide, and linoleic acid hydroperoxide with glutathione, but not of phosphatidylcholine hydroperoxide. GSHPx-GI mRNA was readily detected in human liver and colon, and occasionally in human breast samples, but not other human tissues including kidney, heart, lung, placenta, or uterus. In rodent tissues, GSHPx-GI mRNA is only detected in the gastrointestinal tract, and not in other tissues including liver. In fact, GSHPx-GI appears to be the major glutathione-dependent peroxidase activity in rodent GI tract. This finding suggests that GSHPx-GI could play a major role in protecting mammals from the toxicity of ingested lipid hydroperoxides. In conclusion, we have demonstrated that GSHPx-GI is the fourth member in the selenium-dependent glutathione peroxidase family, in addition to GSHPx-1, GSHPx-P, and phospholipid hydroperoxide glutathione peroxidase (PHGPX).

Amino Acid Sequence↗
PubMed1996

Scavenging of oxygen radicals by heme peroxidases.

The reactions of two heme peroxidases, horseradish peroxidase and lactoperoxidase and their compounds II (oxoferryl heme intermediates, Fe(IV) = O or ferric protein radical Fe(III)R.) and compounds III (resonance hybrids [Fe(III)-O2-.<--> Fe(II)-O2] with superoxide radical anion generated enzymatically or radiolytically, and with hydroxyl radicals generated radiolytically, were investigated. It is suggested that only the protein radical form of compound II of lactoperoxidase reacts with superoxide, whereas compound II of horseradish peroxidase, which exists only in oxoferryl form, is unreactive towards superoxide. Compound III of the investigated peroxidases does not react with superoxide. The lactoperoxidase activity loss induced by hydroxyl radicals is closely related to the loss of the ability to form compound I (oxoferryl porphyrin pi-cation radical, Fe(IV) = O(Por+.) or oxoferryl protein radical Fe(IV) = O(R.)). On the other hand, the modification of horseradish peroxidase induced by hydroxyl radicals has been reported to cause also restrictions in substrate binding (Gebicka, L. & Gebicki, J.L., 1996, Biochimie 78, 62-65). Nevertheless, it has been found that only a small fraction of hydroxyl radicals generated homogeneously does inactivate the enzymes.

Animals↗
PubMed1997

Stability and stabilization of recombinant peroxidase in reversed micelles.

Stability of recombinant peroxidase lacking carbohydrate residues on the surface of the protein molecule has been characterized in reversed micelles of Aerosol OT in octane. The enzyme stability was found to depend on the surfactant hydration degree (w0 = [H2O]/[AOT]). Residual activity after 1 h incubation dropped to zero at w0 = 7 but was 54% at w0 = 25. However, the residual activity levels at all values of hydration degree were definitely low compared to that of glycosylated wild-type horseradish peroxidase. The stability of the enzyme apparently depends on the presence of carbohydrate residues. Stabilization of recombinant peroxidase in reversed micellar system involved sugar-containing co-surfactants such as Tweens and Spans is proposed. As an example, addition of 1 mM Span 80 (1% relative to AOT concentration) increased the recombinant peroxidase stability up to that of wild-type peroxidase.

Detergents↗
PubMed1997

Oxidation of phenothiazines by human term placental peroxidase in non-smokers.

Several phenothiazine derivatives have been shown to cause reproductive toxicity. The biochemical mechanisms responsible for these effects are not fully understood at present. In this study, we investigated hydrogen peroxide-dependent oxidation of seven phenothiazines by purified human term placental peroxidase. Promazine was employed as the prototype phenothiazine drug. Promazine was easily oxidized to a cation radical (absorption maximum at 513 nm) when incubated under acidic conditions with human term placental peroxidase in the presence of hydrogen peroxide. The rate of the radical formation was 350 +/- 30 nmol/min/mg protein when 30 micrograms of the purified peroxidase was incubated with 10 mM promazine and 1.0 mM hydrogen peroxide in acetate buffer pH 3.5. The reaction was linear with respect to time, exhibited dependence on the amount of enzyme, and the concentration of promazine and hydrogen peroxide. Collectively, the results suggest an enzymatic nature of the reaction. Reduced glutathione, ascorbate, and NADH suppressed the rate of promazine radical formation presumably by its reduction back to promazine in a concentration-dependent manner. Concomitantly, NADH was co-oxidized. The cation radical formation and NADH oxidation declined significantly by potassium cyanide and sodium azide, the known peroxidase inhibitors. The enzyme also oxidized chlorpromazine, triflupromazine, trifluoperazine, trimeprazine, fluphenazine, and perphenazine in the presence of hydrogen peroxide. The evidence gathered in this study suggests that peroxidative bioactivation of phenothiazines to their corresponding cation radical species by the human placental peroxidase may represent one of the biochemical mechanisms responsible for the reported developmental toxicity of these chemicals.

Antipsychotic Agents↗
PubMed1997

[Effects of local treatment with sodium fluoride mouthrinse on peroxidase and hypothiocyanite saliva levels in adolescent]/.

The present work describes and analyzes the results of a randomized clinical trial on adolescents (age 18.2 +/- 0.6) carried out in order to evaluate the effects of a twice daily mouthrinse application containing xylitol, sorbitol, sacarine, ciclamate, aspartame, chlorhexidine, hexetidine or NaF for 14 days on amylase, peroxidase, thiocyanate, hypothiocyanite, secretory IgA and total proteins in whole saliva. No significative changes were observed in health and bucodental parameters nor in flow salivary rate, protein, secretory Ig A, or thiocyanate levels as a consequence of the mouthrinses application. On the other hand, NaF treatment (0.02%, 0.05% or 0.1%) did cause an increase in salivary peroxidase and hypothiocyanite, being the former increase higher than the second one. Peroxidase increase was proportional to the mouthrinse dose (r = 0.78; p < 0.01), but not to the hypothiocyanite increase (r = 0.407; p = 0.12). Since the adolescents' health condition was the adequate, it is suggested that the peroxidase increase was due to a higher enzyme synthesis and/or secretion by the parotid and/or submaxillar glands. It is concluded that the increases in salivary peroxidase and hypothiocyanite caused by the NaF treatment favour the host, as they potentiate one of the mechanisms that modulate dental plaque composition, preventing in such a way the colonization by cariogenic pathogens.

Adolescent↗
PubMed1999

Interference of plant peroxidases with guaiac-based fecal occult blood tests is avoidable.

Peroxidase-rich fruits and vegetables are reputed to interfere with guaiac-based fecal occult blood tests. We added horseradish peroxidase to fecal samples and tested them with Hemoccult, Hemoccult SENSA(R), and hydrated Hemoccult. Positivity rates with Hemoccult and Hemoccult SENSA decreased rapidly as the time between smearing (preparation) and development increased, whereas they remained high with hydrated Hemoccult. For samples with added blood, positivity rates did not decrease with time. When 61 volunteers were tested on a standard restriction and on a challenge diet high in plant peroxidase, no positive results occurred during standard restriction. During the challenge diet, one volunteer was positive with Hemoccult and Hemoccult SENSA when development was delayed 24 h, and no volunteers were positive when it was delayed 48 h and 72 h. However, with hydrated Hemoccult, positives occurred in 13 of 61 volunteers at 24 h, 8 of 61 at 48 h, and 5 of 61 at 72 h. Thus, peroxidase-rich plant foods do not need to be excluded from the diet with Hemoccult and Hemoccult SENSA if development is delayed for at least 48 h after smearing. A delay of this duration will not solve the problem of plant peroxidase interference with hydrated Hemoccult.

Adolescent↗
PubMed1989

The one-electron oxidation of porphyrins to porphyrin pi-cation radicals by peroxidases: an electron spin resonance investigation.

For the first time, the enzymatic one-electron oxidation of several naturally occurring and synthetic water-soluble porphyrins by peroxidases was investigated by ESR and optical spectroscopy. The ESR spectra of the free radical metabolites of the porphyrins were singlets (g = 2.0024, delta H = 2-3 G), which we assigned to their respective porphyrin pi-cation free radicals. Several porphyrins were investigated and ranked by the intensity of their ESR spectra (coproporphyrin III greater than coproporphyrin I greater than deuteroporphyrin IX greater than mesoporphyrin IX greater than Photofrin II greater than protoporphyrin IX greater than uroporphyrin I greater than uroporphyrin III greater than hematoporphyrin IX). The porphyrins were oxidized by several peroxidases (horseradish peroxidase, lactoperoxidase, and myeloperoxidase), yielding the same type of ESR spectra. From these results, we conclude that porphyrins are substrates for peroxidases. The changes in the visible absorbance spectra of the porphyrins during enzymatic oxidation were monitored. The two-electron oxidation product, which was assigned to the dihydroxyporphyrin, was detected as an intermediate of the oxidation process. The optical spectrum of the porphyrin pi-cation free radical was not detected, probably due to its low steady-state concentration.

Coproporphyrins↗
PubMed1986

Different metabolism by mammalian and horseradish peroxidases in vitro of steroidal estrogens and their catechol metabolites.

Radioactively labeled estradiol-17 beta and 17 alpha-ethynylestradiol and their 2-hydroxy derivatives were incubated with either horseradish peroxidase or mouse uterus peroxidase, and the formation of polar products, which could not be extracted with diethyl ether, and of ether-extractable metabolites was studied. Moreover, the extent of DNA binding was determined. The different peroxidases gave rise to different products, indicating that different pathways in the metabolism of these steroidal estrogens are catalysed by the two peroxidases.

Animals↗
PubMed2005

The plant multigenic family of thiol peroxidases.

Thiol peroxidases are ubiquitous recently characterized heme-free peroxidases, which catalyze the reduction of peroxynitrites and of various peroxides by catalytic cysteine residues and thiol-containing proteins as reductants. In plants, five different classes can be distinguished, according to the number and the position of conserved catalytic cysteines. Four classes are defined as peroxiredoxins and were already identified by phylogenetic sequence analysis, 1-Cys, 2-Cys, type II, and type Q peroxiredoxins, and the fifth is represented by glutathione peroxidases, which were recently shown to possess a thioredoxin-dependent activity in plants. Since the discovery of peroxiredoxins in plants in 1996, a lot of work has been devoted to the biochemical and functional characterization of the different peroxiredoxin isoforms, but in contrast, few structural data are available. The analysis of the Arabidopsis thaliana genome indicates that at least 17 isoforms of thioredoxin-dependent peroxidases are expressed in various plant compartments. The role of these proteins is discussed in terms of electron donor and substrate specificities and in light of their expression and localization. These enzymes are expressed in many plant tissues and are involved notably in the protection of the photosynthetic apparatus, in the response to various biotic or abiotic stresses by fighting reactive oxygen or nitrogen species and lipid peroxidation.

Arabidopsis↗