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PubMed1992

Heterogeneity and regulation of manganese peroxidases from Phanerochaete chrysosporium.

Lignin and Mn peroxidases are two families of isozymes produced by the lignin-degrading fungus Phanerochaete chrysosporium under nutrient nitrogen or carbon limitation. We purified to homogeneity the three major Mn peroxidase isozymes, H3 (pI = 4.9), H4 (pI = 4.5), and H5 (pI = 4.2). Amino-terminal sequencing of these isozymes demonstrates that they are encoded by different genes. We also analyzed the regulation of these isozymes in carbon- and nitrogen-limited cultures and found not only that the lignin and Mn peroxidases are differentially regulated but also that differential regulation occurs within the Mn peroxidase isozyme family. The isozyme profile and the time at which each isozyme appears in secondary metabolism differ in both nitrogen- and carbon-limited cultures. Each isozyme also responded differently to the addition of a putative inducer, divalent Mn. The stability of the Mn peroxidases in carbon- and nitrogen-limited cultures was also characterized after cycloheximide addition. The Mn peroxidases are more stable in carbon-limited cultures than in nitrogen-limited cultures. They are also more stable than the lignin peroxidases. These data collectively suggest that the Mn peroxidase isozymes serve different functions in lignin biodegradation.

Amino Acid Sequence↗
PubMed1998

Legionella pneumophila catalase-peroxidases: cloning of the katB gene and studies of KatB function.

Legionella pneumophila, the causative organism of Legionnaires' pneumonia, is spread by aerosolization from man-made reservoirs, e.g. , water cooling towers and air conditioning ducts, whose nutrient-poor conditions are conducive to entrance into stationary phase. Exposure to starvation conditions is known to induce several virulence traits in L. pneumophila. Since catalase-peroxidases have been extremely useful markers of the stationary-phase response in many bacterial species and may be an avenue for identifying virulence genes in L. pneumophila, an investigation of these enzymes was initiated. L. pneumophila was shown to contain two bifunctional catalase-peroxidases and to lack monofunctional catalase and peroxidase. The gene encoding the KatB catalase-peroxidase was cloned and sequenced, and lacZ fusion and null mutant strains were constructed. Null mutants in katB are delayed in the infection and lysis of cultured macrophage-like cell lines. KatB is similar to the KatG catalase-peroxidase of Escherichia coli in its 20-fold induction during exponential growth and in playing a role in resistance to hydrogen peroxide. Analysis of the changes in katB expression and in the total catalase and peroxidase activity during growth indicates that the 8- to 10-fold induction of peroxidase activity that occurs in stationary phase is attributable to KatA, the second L. pneumophila catalase-peroxidase.

Amino Acid Sequence↗
PubMed2006

Mechanism of activation of cytochrome C peroxidase activity by cardiolipin.

In this work, the actions of bovine heart cardiolipin, synthetic tetraoleyl cardiolipin, and a nonspecific anionic detergent sodium dodecyl sulfate (SDS) on cytochrome c (Cyt c) peroxidase activity recorded by chemiluminescence in the presence of luminol and on the Fe...S(Met80) bond whose presence was estimated by a weak absorption band amplitude with peak at 695-700 nm (A(695)) were compared. A strict concurrency between Fe...S(Met80) breaking (A(695)) and cytochrome peroxidase activity enhancement was shown to exist at cardiolipin/Cyt c and SDS/Cyt c molar ratios of 0 : 1 to 50 : 1 (by chemiluminescence). Nevertheless, when A(695) completely disappeared, Cyt c peroxidase activity under the action of cardiolipin was 20 times more than that under the action of SDS, and at low ligand/protein molar ratios (=4), SDS failed to activate peroxidase activity while cardiolipin enhanced Cyt c peroxidase activity 16-20-fold. A(695) did not change on Cyt c binding with liposomes consisting of tetraoleyl cardiolipin and phosphatidylcholine (1 : 10 : 10), while peroxidase activity was enhanced by a factor of 8. Breaking of 70% of the Fe...S(Met80) bonds resulted in only threefold enhancement of peroxidase activity. Cardiolipin-activated Cyt c peroxidase activity was reduced by high ionic strength solution (1 M KCl). The aggregated data suggest that cardiolipin activating action is caused, first, by a nonspecific effect of Fe...S(Met80) breaking as the result of conformational changes in the protein globule caused by the protein surface electrostatic recharging by an anionic amphiphilic molecule, and second, by a specific acceleration of the peroxidation reaction which is most likely due to enhanced heme accessibility for H(2)O(2) as a result of the hydrophobic interaction between cardiolipin and cytochrome.

Animals↗
PubMed1991

Interleukin 6 inhibits human thyroid peroxidase gene expression.

It has been reported that cytokines, especially interleukin 1 and interferon-gamma, inhibit the thyroid hormone secretion and the gene expression of human thyroid peroxidase and thyroglobulin. Interleukin 6 has recently been found to be an important cytokine for the regulation of immunoendocrine interaction and intrathyroidal production of interleukin 6 has been reported. Therefore, we investigated the regulation of thyroid hormone secretion and thyroid peroxidase messenger RNA by interleukin 6 in human thyrocytes to clarify further the functional role of interleukin 6 in thyroid glands. Thyrocytes dispersed from Graves' thyroid tissues were incubated with TSH with or without interleukin 6. TSH (5 U/l) stimulated the expression of thyroid peroxidase mRNA transcripts (4.0, 3.2, 2.1, and 1.7 kb, respectively), although unstimulated thyrocytes contained the low level of 3.2 kb thyroid peroxidase mRNA transcript. Interleukin 6 (10(4)-10(5) U/l) inhibited TSH-induced thyroid peroxidase mRNA in a dose-dependent manner, although the basal level of thyroid peroxidase mRNA expression was not suppressed by interleukin 6. Interleukin 6 also inhibited 8-bromo-cyclic adenosine monophosphate-induced thyroid peroxidase mRNA levels. In contrast, the gamma-action mRNA hybridization signal was not altered in control or treated cells. Subsequently, interleukin 6 inhibited TSH-induced T3 secretion in a dose-dependent manner after 72 h treatment. However, interleukin 6 did not affect DNA synthesis. Pretreatment with specific antibody against interleukin 6 selectively restored the inhibitory effect of interleukin 6 on thyroid peroxidase gene expression. Our results suggest that interleukin 6 plays an inhibitory role in the thyroid gland, in addition to interleukin 1 and interferon gamma.

Blotting, Northern↗
PubMed1996

A simplified method for the estimation of glutathione peroxidase activity and selenium concentration in bovine blood.

Twelve hybridoma clones were established that produced mouse monoclonal antibodies to bovine erythrocyte glutathione peroxidase. In these monoclonal antibodies, GPF-1, GPI-2, and GPJ-1, which showed marked reaction to this enzyme, were examined for reactivity to erythrocyte lysates from 12 different species of animals and from humans and for the inhibition of glutathione peroxidase activity. GPF-1 and GPJ-1 reacted markedly with glutathione peroxidase in erythrocyte lysates from ruminants and pigs and inhibited enzymatic activity. Conversely, GPI-2 showed positive reaction to hemolysate from all mammals used, except for mice, and did not inhibit enzymatic activity. To determine the concentration of bovine glutathione peroxidase in erythrocyte lysates, a sandwich ELISA was developed using GPJ-1, both as a coated antibody and as a peroxidase-labeled antibody. This ELISA system was a sensitive procedure with a detection limit of 6 ng/ml for glutathione peroxidase protein. Using blood samples from 121 cows, optical density by this ELISA was well correlated with the glutathione peroxidase activity and with the selenium concentration in bovine whole blood. The sandwich ELISA using GPJ-1 is a rapid and simple screening method to estimate glutathione peroxidase activity and selenium concentration in bovine whole blood.

Animals↗
PubMed1999

Halide peroxidase in tissues that interact with bacteria in the host squid Euprymna scolopes.

An enzyme with similarities to myeloperoxidase, the antimicrobial halide peroxidase in mammalian neutrophils, occurs abundantly in the light organ tissue of Euprymna scolopes, a squid that maintains a beneficial association with the luminous bacterium Vibrio fischeri. Using three independent assays typically applied to the analysis of halide peroxidase enzymes, we directly compared the activity of the squid enzyme with that of human myeloperoxidase. One of these methods, the diethanolamine assay, confirmed that the squid peroxidase requires halide ions for its activity. The identification of a halide peroxidase in a cooperative bacterial association suggested that this type of enzyme can function not only to control pathogens, but also to modulate the interactions of host animals with their beneficial partners. To determine whether the squid peroxidase functions under both circumstances, we examined its distribution in a variety of host tissues, including those that typically interact with bacteria and those that do not. Tissues interacting with bacteria included those that have specific cooperative associations with bacteria (i.e., the light organ and accessory nidamental gland) and those that have transient nonspecific interactions with bacteria (i.e., the gills, which clear the cephalopod circulatory system of invading microorganisms). These bacteria-associated tissues were compared with the eye, digestive gland, white body, and ink-producing tissues, which do not typically interact directly with bacteria. Peroxidase enzyme assays, immunocytochemical localization, and DNA-RNA hybridizations showed that the halide-dependent peroxidase is consistently expressed in high concentration in tissues that interact bacteria. Elevated levels of the peroxidase were also found in the ink-producing tissues, which are known to have enzymatic pathways associated with antimicrobial activity. Taken together, these data suggest that the host uses a common biochemical response to the variety of types of associations that it forms with microorganisms.

Animals↗
PubMed1998

Drought stress, peroxidase activity and formaldehyde metabolism in bean plants.

In our investigations we have studied the changes of total peroxidase and isozyme activities, peroxidase isozyme pattern and the level of endogenous formaldehyde and trigonelline. We have examined the effect of drought stress resulted by Carbowax treatment (2, 5, 7, 10%) of two different snap bean (Phaseolus vulgaris L.) genotypes [drought tolerant (T) and drought sensitive (S)]. There were no detectable differences in the peroxidase isozyme patterns but the total peroxidase activity was increased. We have found similar steep enhancement in the peroxidase activities of one of three peroxidase fractions while the increase in the other isozyme fractions was not so significant in the two genotypes. Increasing peroxidase activities and changes in the amount of endogenous formaldehyde and trigonelline were detectable with increasing Carbowax treatment in both genotypes, but in different ways. According to our experiments, the total peroxidase and some isozyme activity correlated with the concentration of endogenous formaldehyde and trigonelline, playing an important role during drought stress.

Chromatography, High Pressure Liquid↗
PubMed1976

Peroxidase activity of alveolar macrophages.

Peroxidase activity was studied in alveolar macrophages and compared to the peroxidase activity in polymorphonuclear leukocytes using cytochemical techniques. A dense reaction product for peroxidase was observed in the primary lysosomes of polymorphonuclear leukocytes, but no significant peroxidase or peroxidative enzymes could be detected in rabbit alveolar macrophages. Furthermore, following vigorous phagocytosis of zymosan particles by alveolar macrophages in vitro, no peroxidase could be detected in association with the phagocytic vacuole. Exogenous horseradish peroxidase was ingested readily by alveolar macrophages so that abundant reaction product was demonstrated in pinocytotic vesicles and phagocytic vacuoles. The uptake of exogenous peroxidase by pinocytosis appeared to be more vigorous in alveolar macrophages than in polymorphonuclear leukocytes. These studies demonstrate that alveolar macrophages do not contain significant quantities of peroxidase and suggest that, it contrast to polymorphonuclear leukocytes, peroxidative metabolism does not contribute in a major way to microbial killing by alveolar macrophages.

Animals↗
PubMed1992

Improved accuracy in diagnostic immunohistochemistry, lectin histochemistry and in situ hybridization using a gold-labeled horseradish peroxidase antibody and silver intensification.

BACKGROUND: Improvements in the use of the avidin-biotin peroxidase complex technique and direct as well as indirect labeled avidin-biotin methods for application in diagnostic immunohistochemistry, lectin histochemistry and in situ hybridization are reported. The new technology combines the advantages of immunoenzyme and immunogold silver staining techniques and can be performed on routinely fixed and paraffin-embedded tissues. EXPERIMENTAL DESIGN: The basic modification of the labeling procedures was introduced at the final revealing step. The histochemical visualization of catalytic activity of horseradish peroxidase by the diaminobenzidine reaction was replaced by the detection of horseradish peroxidase immunoreactivity using anti-horseradish peroxidase-gold complexes and their intensification with silver acetate which is relatively light insensitive. RESULTS: The use of gold-labeled anti-horseradish peroxidase antibodies eliminates the need for quenching of endogenous peroxidase activity. Furthermore, the immunogold silver staining provides improved lateral resolution, higher contrast, and lower background staining as compared with the diaminobenzidine reaction. The new technology has been applied for the localization of different polypeptides in endocrine cells, cytoskeletal elements, cell surface receptors, basal lamina type IV collagen, endothelial cell marker, lectin binding sites, and DNA of various viruses. CONCLUSIONS: We concluded that the anti-horseradish peroxidase-gold complex is of general use in a variety of techniques applying horseradish peroxidase as a marker and should be a valuable alternative to existing enzyme substrate techniques.

Gold↗
PubMed2004

Contribution of peroxidases in host-defense, diseases and cellular functions.

Peroxidases figure prominently in biology and contribute significantly to cell biology, host defense against infection, and pathogenesis of several inflammatory diseases. These varied and diverse aspects of peroxidase biochemistry and its clinical implications will be the subjects of in-depth analysis at the 4th International peroxidase meeting held in Kyoto. Specific topics range from the molecular basis of peroxidase structure and function to the clinical consequences of autoantibodies generated against myeloperoxidase (MPO), the peroxidase present in circulating neutrophils. Consideration of novel aspects of peroxidase biology, both unanticipated biochemical properties of MPO and the potential role of MPO in the pathogenesis of inflammatory diseases such as atherosclerosis, will also be included. In addition to peroxidases, the newly expanded family of NADPH oxidases will be discussed. We hope that this collection of scientists who share a common interest in peroxidase biology but each possess expertise in distinctly different aspects of the subject will provide a setting for spirited discussion and a lively exchange of views to yield advances in understanding and to create new applications of those insights to benefit clinical medicine, agriculture and industry.

Animals↗
PubMed1988

Notes on the peroxidase activity of human basophil leukocytes.

In recent years, basophils have been described as peroxidase-positive in some textbooks (6, 8). However, as far as basophils in the peripheral blood from healthy persons are concerned, they must be considered as peroxidase-negative. This discrepancy is thought to be based on the following points: 1) fixation of human basophils is more difficult than that of the other leukocytes; 2) counterstaining with a certain basic dye causes misinterpretation of the enzyme reaction; 3) diaminobenzidine which has been most frequently used as hydrogen donor in the peroxidase reaction is so sensitive to non-enzymatic substances that substrate-minus experiments as well as inhibition experiments for peroxidase are absolutely necessary; and 4) basophils in the peripheral blood from healthy persons are originally peroxidase-negative. On the other hand, basophils in the peripheral blood from patients with myeloid leukemia are frequently peroxidase-positive, and yet, the peroxidase demonstrated in such basophils is not true myeloperoxidase since peroxidase from the above patients is resistant to heating, methanol and other chemicals known as inhibitors of myeloperoxidase. These data are illustrated by many color photographs.

Basophils↗
PubMed1987

Endogenous peroxidase activity as a marker of macrophage renewal during BCG-induced inflammation in the rat lung.

To determine whether the cytochemical localization of peroxidase activity could be used as a marker of monocyte influx into the lung during an inflammatory response, the authors studied the peroxidase phenotypes of lavaged alveolar macrophages from rats with bacille Calmette-Guérin (BCG)-induced pulmonary inflammation. Rats were immunized subcutaneously and 2 weeks later intravenously with BCG. During the early phase of pulmonary inflammation, an increase was observed in the numbers of alveolar macrophages with no peroxidase activity in the endoplasmic reticulum. These cells appeared to reflect monocyte influx into the injured lung. The later stages of inflammation were characterized by increased numbers of alveolar macrophages with peroxidase-positive endoplasmic reticulum, probably due to activation of enzymatic activity in situ. During the early phase, peroxidase activity was also observed within macrophage cytoplasmic inclusions, probably representing both primary monocyte lysosomes and internalized myeloperoxidase from inflammatory neutrophils. Serial observations indicated that the peroxidase-positive cytoplasmic inclusions became negative with time. It is concluded that inflammation-induced modulation of peroxidase activity in the endoplasmic reticulum and in cytoplasmic inclusions makes the alveolar macrophage peroxidase phenotype no more than a rough marker of monocyte influx into the inflamed lung.

Animals↗
PubMed1987

Characterization of the major hydroperoxide-reducing activity of human plasma. Purification and properties of a selenium-dependent glutathione peroxidase.

We have recently characterized the major hydroperoxide-reducing enzyme of human plasma as a glutathione peroxidase (Maddipati, K. R., Gasparski, C., and Marnett, L. J. (1987) Arch. Biochem. Biophys. 254, 9-17). We now report the purification and kinetic characterization of this enzyme. The purification steps involved ammonium sulfate precipitation, hydrophobic interaction chromatography on phenyl-Sepharose, anion exchange chromatography, and gel filtration. The purified peroxidase has a specific activity of 26-29 mumol/min/mg with hydrogen peroxide as substrate. The human plasma glutathione peroxidase is a tetramer of identical subunits of 21.5 kDa molecular mass as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and is different from human erythrocyte glutathione peroxidase. The plasma peroxidase is a selenoprotein containing one selenium per subunit. Unlike several other glutathione peroxidases this enzyme exhibits saturation kinetics with respect to glutathione (Km for glutathione = 4.3 mM). The peroxidase exhibits high affinity for hydroperoxides with Km values ranging from 2.3 microM for 13-hydroperoxy-9,11-octadecadienoic acid to 13.3 microM for hydrogen peroxide at saturating glutathione concentration. These kinetic parameters are suggestive of the potential of human plasma glutathione peroxidase as an important regulator of plasma hydroperoxide levels.

Electrophoresis, Polyacrylamide Gel↗
PubMed1994

A di-heme cytochrome c peroxidase from Nitrosomonas europaea catalytically active in both the oxidized and half-reduced states.

A di-c-heme containing cytochrome (cytochrome c553 peroxidase) has been isolated from the chemoautotrophic bacterium Nitrosomonas europaea. Sequence analysis of the N terminus and the two heme-containing peptides generated by digestion of the enzyme with trypsin show 40% homology overall to sequences reported for the di-heme peroxidase from Pseudomonas aeruginosa (Rönnberg, M., Kalkkinen, N., and Ellfolk, N. (1989) FEBS Lett. 250, 175-178). At room temperature and pH 7.0, one heme is low spin with Em7 = +450 mV and the other is high spin with Em7 = -260 mV. EPR spectra show a mixture of high spin and low spin signals at cryogenic temperatures. Anionic ligands (CN-, N3-, F-, CNO-) bind so as to perturb the high spin heme when cytochrome c553 peroxidase is either fully oxidized (FeLS3+:FeHS3+) or half-reduced (FeLS2+:FeHS3+). The EPR signal of the high potential, low spin heme in fully oxidized enzyme is unperturbed by the presence of the ligands. Furthermore, each ligand results in similar characteristic EPR signals for either oxidation state of the peroxidase. Both the fully oxidized and half-reduced oxidation states of cytochrome c553 peroxidase are catalytically active as evidenced by the enzyme's ability to oxidize horse heart cytochrome c in the presence of H2O2, as well as by optical changes associated with the addition of H2O2 to the peroxidase. In the presence of stoichiometric amounts of H2O2, the half-reduced enzyme is rapidly oxidized and the fully oxidized enzyme shows a significant decrease in absorbance in the Soret region of the optical spectrum coupled with a lesser increase near 600-650 nm. These latter optical changes are similar to what is observed in the formation of a porphyrin cation radical. This suggests that this di-heme peroxidase may form a compound I intermediate analogous to that formed by horseradish peroxidase.

Amino Acid Sequence↗
PubMed1977

Studies in neuronal ceroid-lipofuscinosis: leukocyte peroxidase deficiency in a patient with neuronal ceroid-lipofuscinosis (Jansky-Bielschowsky type).

Leukocyte peroxidase deficiency has been demonstrated in a confirmed case of neuronal ceroid-lipofuscinosis with guaiacol, o-dianisidine, and p-phenylenediamine used as hydrogen donors in the peroxidase assay system. Nitroblue tetrazolium (NBT) reduction values in the leukocytes of the patient were also found to be significantly higher than those of normal controls, indicating the impaired hydrogen peroxide catabolism. When the patient was given a daily dose of vitamin E (400 I.U.), vitamin C (1 gm), and methionine (1 gm.) along with a weekly intramuscular injection of vitamin B12, the leukocyte peroxidase values of the patient returned to normal levels in about 7 weeks. NBT reductions values also decreased to normal levels. The regenerated enzyme in the patient's leukocytes was shown to have similar chromatographic and electrophoretic properties as the leukocyte peroxidase of normal controls. After about 28 weeks of therapy, the peroxidase levels in the leukocytes of the patient returned to original low levels, with concomitant increase in the NBT reduction values. The effect of vitamin therapy on normal control subjects was, at least in some cases, an increase of leukocyte peroxidase. A significant increase in the peroxidase levels of the patient's leukocytes during vitamin therapy remains unexplained, and the possibility of peroxidase deficiency being a secondary manifestation rather than the primary defect in Batten's disease cannot be ruled out.

Ascorbic Acid↗
PubMed1996

Modulation of embryonic glutathione peroxidase activity and phenytoin teratogenicity by dietary deprivation of selenium in CD-1 mice.

Selenium (Se)-dependent and -independent glutathione (GSH) peroxidases detoxify H2O2 and lipid hydroperoxides, which may mediate the teratogenicity of phenytoin and related xenobiotics. To test this hypothesis, CD-1 mice were placed on Se-deficient diets for 15, 25 or 40 days and bred so that the day of analysis corresponded to gestational day 11. In Se-replete control animals, embryonic peroxidase activities were only 5% of activities in maternal liver (P < .05). After 15 days of Se deprivation, maternal activities for H2O2 (reflecting Se-dependent peroxidase) and cumene hydroperoxide (CmOOH) (reflecting both Se-dependent and -independent peroxidases) were reduced to 20% (P < .05) and 35% of controls, respectively. At this time, the incidence of fetal cleft palates initiated by phenytoin (55 mg/kg intraperitoneally on gestational days 11, 12 and 13) was doubled, from 12% to 25% (P < .05). Selenite rescue (Na2SeO3, 350 micrograms/kg intraperitoneally on day 9) restored maternal and embryonic peroxidase activities and completely inhibited phenytoin-initiated postpartum lethality and fetal resorptions in animals that had been Se depleted for 15 days. After 40 days of Se deprivation, maternal and embryonic peroxidase/H2O2 activities were reduced to < 1% and 27% of Se-replete controls, respectively. In contrast, maternal peroxidase/CmOOH activity was increased to 70% of controls, reflecting induction of Se-independent peroxidase, compared with that with 15 days' depletion. Phenytoin-initiated cleft palates with 40 days' depletion appeared to be reduced (16%) compared with Se-replete controls (24%) (P < .07). In 40-day Se-depleted animals given selenite rescue, the 10% incidence of cleft palates was significantly lower than that in the 40-day Se-replete group (24%) but not the Se-depleted group (16%). This is the first demonstration of reduced Se-dependent GSH peroxidase activities in embryonic tissues with dietary Se-deprivation. The results implicate reactive oxygen species and lipid hydroperoxides in the mechanism of phenytoin teratogenicity and suggest that GSH peroxidases are important embryoprotective enzymes.

Abnormalities, Drug-Induced↗
PubMed1998

Ascorbic acid-dependent cytoprotection of ovarian cells by leukocyte and nonleukocyte peroxidases.

Luteal cells contain high levels of ascorbic acid that is secreted by stimulation with agents like luteinizing hormone (LH) and prostaglandin F2 alpha (PGF2 alpha). One role for interstitial ascorbic acid, we propose, may be the detoxification of H2O2 by regeneration of catalytically active peroxidase. By serving as a preferred secondary substrate, ascorbic acid regenerates the catalytically active peroxidase that is inhibited irreversibly by H2O2 alone. To test this hypothesis, luteal cells were incubated in the absence and presence of peroxidases and H2O2, and the maximal cyclic AMP and steroidogenic response to LH was examined. In luteal cells, H2O2 is known to severely inhibit LH-sensitive cyclic AMP accumulation and steroidogenesis, and the addition of lactoperoxidase, myeloperoxidase, eosinophil peroxidase, or ascorbic acid (1 mM) alone had no effect on these responses to H2O2. However, co-incubation of ascorbic acid and the peroxidases completely reversed the inhibition of cyclic AMP accumulation and steroidogenesis produced by H2O2. These findings and the results that show direct oxidation of ascorbic acid in the presence of peroxidase and H2O2, but not with H2O2 alone, support the conclusion that ascorbic acid released from cells may detoxify H2O2 by regenerating the catalytically active state of peroxidases.

Animals↗
PubMed1999

Expression of eosinophil peroxidase in the immature basophil cell line KU812-F.

Although peroxidase activity in basophils can be detected by optical and ultrastructural cytochemistry, its characteristics remain to be determined. We have demonstrated the characteristics of peroxidase activity induced in the immature basophil cell line, KU812-F. Ultrastructurally, peroxidase activity was detected in granules as well as in the perinuclear space and endoplasmic reticulum. Immunocytochemistry revealed that KU812-F cells were stained by anti-eosinophil peroxidase antibodies, and eosinophil peroxidase mRNA, not myeloperoxidase, was detected in the cells using Northern hybridization and reverse transcription-polymerase chain reaction. Eosinophil peroxidase can be one of the molecules shared with eosinophils and basophils. The biological function of eosinophil peroxidase detected in basophils remains uncertain.

Basophils↗