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PubMed1977

Purification of bovine thyroid peroxidase.

Trypsin-solubilized peroxidase activity from beef subcellular particles was resolved by DEAE-cellulose chromatography into 5 fractions, which contained enzymatically active components that ranged in molecular size from 73,000 to 340,000 daltons. The most active fraction (mol wt, 92,000 by gel filtration) was further purified (59,000-fold overall) by chromatography on hydroxylapatite. This highly purified peroxidase preparation had an absorbance purity ratio (A410:A280) of 0.55 and oxidized iodide (I3-formation) and guaiacol at rates of 300 and 460 micronmol/min/mg, respectively, which were about 3 and 1 1/2 times, respectively, greater than any previously described preparations. The enzyme was contaminated with an inactive protein of equal size. The highly purified peroxidase preparation lost its activity within a few days even when stored at -15 C with iodide. Two of the other DEAE-cellulose fractions contained peroxidase components with estimated sizes (gel filtration) of 73,000, 96,000, and 98,000, which were further purified purified (1,600 and 15,600 fold) on hydroxylapatite. They were 1/4 to 1/40 as active as the highly purified preparation and also became increasingly labile on purification. The remaining two DEAE-cellulose fractions were heterogeneous mixtures of stable peroxidase components whose average molecular sizes (gel filtration) were 220,000, 300,000, and 340,000 daltons, and which were not amenable to further purification on hydroxylapatite. The ratio of guaiacol to iodide activity decreased from 3.0 in the particles to about 1.5 in the highly purified preparations. The turnover numbers of the purest peroxidase component (mol wt. 92,000) for iodide and guaiacol were very similar to those of highly purifed, commericial lacto- and horseradish peroxidases. The pH maxima for iodide oxidation were 7.4, 6.0, and 4.5 for thyroid, lacto-, and horseradish peroxidases, respectively, whereas guaiacol oxidation peaked at pH 7.0-7.8 for all three enzymes. On the basis of these results and the dissimilar molecular sizes reported for trypsin-solubilized thyroid peroxidase by several other investigators, it was concluded that the molecular size is primarily determined by the conditions of proteolysis.

Animals↗
PubMed1990

Hydroxyurea and p-aminophenol are the suicide inhibitors of ascorbate peroxidase.

Guaiacol peroxidase from spinach catalyzes the oxidation of p-aminophenol to produce the aminophenoxy radical as the primary product which is converted further into a stable oxidation product with an absorption peak at 470 nm. The p-aminophenol radicals oxidize ascorbate (AsA) to produce monodehydroascorbate radicals. Kinetic analysis indicates that p-aminophenol radicals also oxidize monodehydroascorbate to dehydroascorbate. Incubation of AsA peroxidase from tea leaves and hydrogen peroxide with p-aminophenol, p-cresol, hydroxyurea, or hydroxylamine results in the inactivation of the enzyme. No inactivation of the enzyme was found upon incubation of the enzyme with these compounds either in the absence of hydrogen peroxide or with the stable oxidized products of these compounds. The enzyme was protected from inactivation by the inclusion of AsA in the incubation mixture. The radicals of p-aminophenol and hydroxyurea were produced by AsA peroxidase as detected by their ESR signals. These signals disappeared upon the addition of AsA, and the signal characteristic of monodehydroascorbate was found. Thus, AsA peroxidase is inactivated by the radicals of p-aminophenol, p-cresol, hydroxyurea, and hydroxylamine which are produced by the peroxidase reaction, and it is protected from inactivation by AsA via the scavenging of the radicals. Thus, these compounds are the suicide inhibitors for AsA peroxidase. Isozyme II of AsA peroxidase, which is localized in chloroplasts, is more sensitive to these compounds than isozyme I. In contrast to AsA peroxidase, guaiacol peroxidase was not affected by these various compounds, even though each was oxidized by it and the corresponding radicals were produced.

Aminophenols↗
PubMed1987

Quantitative studies of hydroperoxide reduction by prostaglandin H synthase. Reducing substrate specificity and the relationship of peroxidase to cyclooxygenase activities.

The peroxidase activity of prostaglandin H (PGH) synthase catalyzes reduction of 5-phenyl-4-pentenyl hydroperoxide to 5-phenyl-4-pentenyl alcohol with a turnover number of approximately 8000 mol of 5-phenyl-4-pentenyl hydroperoxide/mol of enzyme/min. The kinetics and products of reaction establish PGH synthase as a classical heme peroxidase with catalytic efficiency similar to horseradish peroxidase. This suggests that the protein of PGH synthase evolved to facilitate peroxide heterolysis by the heme prosthetic group. Comparison of an extensive series of phenols, aromatic amines, beta-dicarbonyls, naturally occurring compounds, and nonsteroidal anti-inflammatory drugs indicates that considerable differences exist in their ability to act as reducing substrates. No correlation is observed between the ability of compounds to support peroxidatic hydroperoxide reduction and to inhibit cyclooxygenase. In addition, the resolved enantiomers of MK-410 and etodolac exhibit dramatic enantiospecific differences in their ability to inhibit cyclooxygenase but are equally potent as peroxidase-reducing substrates. This suggests that there are significant differences in the orientation of compounds at cyclooxygenase inhibitory sites and the peroxidase oxidation site(s). Comparison of 5-phenyl-4-pentenyl hydroperoxide reduction by PGH synthase and horseradish peroxidase reveals considerable differences in reducing substrate specificity. Both the cyclooxygenase and peroxidase activities of PGH synthase inactivate in the presence of low micromolar amounts of hydroperoxides and arachidonic acid. PGH synthase was most sensitive to arachidonic acid, which exhibited an I50 of 0.6 microM in the absence of all protective agents. Inactivation by hydroperoxides requires peroxidase turnover and can be prevented by reducing substrates. The I50 values for inactivation by 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid are 4.0 and 92 microM, respectively, in the absence and presence of 500 microM phenol, a moderately good reducing substrate. The ability of compounds to protect against hydroperoxide-induced inactivation correlates directly with their ability to act as reducing substrates. Hydroquinone, an excellent reducing substrate, protected against hydroperoxide-induced inactivation when present in less than 3-fold molar excess over hydroperoxide. The presence of a highly efficient hydroperoxide-reducing activity appears absolutely essential for protection of the cyclooxygenase capacity of PGH synthase. The peroxidase activity is, therefore, a twin-edged sword, responsible for and protective against hydroperoxide-dependent inactivation of PGH synthase.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkenes↗
PubMed1985

Characterization of hog thyroid peroxidase.

Several fundamental properties of purified hog thyroid peroxidase (A413 nm/A280 nm = 0.55) were investigated in comparison with bovine lactoperoxidase. The Mr of thyroid peroxidase was 71,000. The prosthetic group of thyroid peroxidase was identified spectrophotometrically as protoheme IX after the enzyme was hydrolyzed with Pronase. Optical spectra of oxidized and reduced thyroid peroxidases and their complexes with azide and cyanide were very similar to lactoperoxidase, except that lactoperoxidase had two reduced forms with the Soret band either at 446 or 435 nm, and thyroid peroxidase lacked a reduced form having the 446-nm band. From comparison of their pyridine hemochrome spectra, epsilon mM at 413 nm of thyroid peroxidase was estimated to be 114, being the same as that of lactoperoxidase. The cyanide inhibition for the reaction of thyroid peroxidase was competitive with hydrogen peroxide and the inhibition constant was in rough accord with the dissociation constant of its cyanide complex measured from spectrophotometric titration. Azide inhibited the reaction with an inhibition constant which was about one one-thousandth of the dissociation constant for its spectrally discernible complex. The azide inhibition was not competitive with hydrogen peroxide and decreased as the reaction proceeded. Aminotriazole inhibited the reaction strongly, and the inhibition was augmented during the reaction. These inhibition patterns of azide and aminotriazole were more or less observed in the reaction of lactoperoxidase, but not in the case of horseradish peroxidase. Characteristics of animal peroxidases are discussed.

Animals↗
PubMed1982

The reactivity of Mg-substituted horseradish peroxidases.

Mg-substituted horseradish peroxidases were oxidized by K2IrCl6 or K3Fe(CN)6 to their porphyrin radical form and the 1:1 stoichiometric relationship was confirmed by spectrophotometric, fluorophotometric, and ESR titration methods. The values of E'0 for oxidations of Mg peroxidases A and C were both 0.63 V at pH 6 and depended on pH in the same way as postulated for the Compound I/Compound II couples of the corresponding enzymes. Unlike Zn peroxidase C, Mg peroxidase C was not directly oxidized by H2O2. The oxidation was catalyzed by the native peroxidase. Mg peroxidase C was photooxidized to the radical form faster than Zn peroxidase C, but its oxidation was accomplished by irreversible changes in the porphyrin in the early stage of reaction. The rate of reduction of the oxidized Mg peroxidases in the presence of various electron donors was measured at varying pH values and compared with the rate of Compound I reduction. A role of porphyrin as a site of electron transfer in the peroxidase catalysis was suggested.

Electron Spin Resonance Spectroscopy↗
PubMed1983

Effects of cytochalasin D and colchicine on the uptake, translocation, and biliary secretion of horseradish peroxidase and [14C]sodium taurocholate in the rat.

The roles of microfilaments and microtubules in the hepatocellular uptake, translocation, and biliary excretion of horseradish peroxidase and [14C]sodium taurocholate were investigated using the microfilament inhibitor cytochalasin D and the microtubule inhibitor colchicine. In separate studies, horseradish peroxidase and [14C]taurocholate were injected separately as a bolus into rat portal veins after treatment with cytochalasin D or colchicine, and bile was collected and analyzed for the presence of horseradish peroxidase and [14C]taurocholate. Cytochalasin D treatment depressed bile flow by approximately 50% and decreased the biliary secretion of [14C]taurocholate in direct proportion to bile flow. Horseradish peroxidase secretion into bile was unaffected, and total biliary protein secretion was decreased only slightly. Because of the depression of bile secretion, concentrations in bile of horseradish peroxidase and total biliary protein increased significantly. Consistent with reported observations of cytochalasin D, decreases in microfilaments and dilated bile canaliculi were observed by electron microscopy; however, the vesicular transport of horseradish peroxidase as observed using electron microscopy cytochemistry appeared to be normal and unaffected by cytochalasin D treatment. Colchicine, in contrast, had minimal effect on bile flow and did not diminish the biliary secretion of [14C]taurocholate. Colchicine inhibited both the total amount of horseradish peroxidase secreted into bile as well as the rate of its secretion in comparison with control and cytochalasin D-treated animals. Cellular morphology was consistent with published observations for colchicine, which included a marked decrease in microtubules. In addition, after electron microscopy cytochemistry there was a paucity of horseradish peroxidase-containing vesicles within the hepatocytes, suggesting that colchicine interfered with the vesicular transport of horseradish peroxidase. Collectively, the data suggest that (a) the mechanism used by hepatocytes for the secretion of bile acids is independent of the vesicular transport of biliary proteins and is dependent upon intact microfilaments and (b) such vesicular transport of protein into bile requires an intact and functioning microtubular network.

Animals↗
PubMed1993

Thiols as peroxidase substrates.

The abilities of haem peroxidases to catalyse the oxidation of various thiols were studied using the spin-trapping electron spin resonance (ESR) technique. Myeloperoxidase, a neutrophil and monocyte enzyme, catalysed the oxidation of cysteamine, cysteine methyl, and ethyl ester and to some extent 2-mercaptoethanol and thioglycollic acid. This peroxidase poorly catalysed the oxidation of cysteine, N-acetylcysteine, penicillamine, and glutathione under the same conditions. The dependence on pH of peroxidase-catalysed thiol oxidation may indicate that the thiolate anion form is the actual peroxidase substrate. Another leucocyte peroxidase, eosinophil peroxidase, had similar catalytic properties toward thiols as myeloperoxidase. Lactoperoxidase (found in milk, saliva, and tears) and the plant horseradish peroxidase were, however, different from the aforementioned leucocyte peroxidases in their abilities to catalyse the oxidation of thiols.

Catalysis↗
PubMed1977

Ultrastructural localization of peroxidase in leukocytes of rat bone marrow and blood.

The differentiation of leukocytes in the bone marrow and blood of normal adult male rats was studied by electron microscopy and peroxidase cytochemistry. Tissue samples were fixed in glutaraldehyde, or paraformaldehyde-glutaraldehyde, and incubated in a peroxidase medium containing 3,3'-diaminobenzidine and H2O2 ad pH 7.6. Mature cells of blood were identified, and then the earlier stages of maturation in bone marrow were analyzed. In immature cells of four cell lines, neutrophils, monocytes, basophils, and eosinophils, peroxidase is synthesized and could be demonstrated in the rough endoplasmic reticulum (RER), Golgi complex, and in cytoplasmic granules. Later in maturation, reaction product for peroxidase could not be found in RER or Golgi complex, indicating that peroxidase synthesis had ceased. In two cell lines, neutrophils and monocytes, peroxidase-negative granules were formed, and the mature cells contained two populations of cytochemically distinct granules. All granules of mature eosinophils were peroxidase-positive. In mature basophils, some granules were clearly peroxidase-positive; others displayed variable density, making interpretation uncertain. Mast cells were never seen in blood, but were abundant in bone marrow; peroxidase was never found in their granules by either electron microscopic cytochemistry or a variety of light microscopic methods. Hence, these cells differ from basophils, not only in morphology but also in the enzyme content of their granules.

Animals↗
PubMed1998

Mechanisms for protection against inactivation of manganese peroxidase by hydrogen peroxide.

It has been reported that cation radicals of aromatic substrates maintain the active form of lignin peroxidase by oxidatively converting compound III, generated during peroxidase turnover, into ferric enzyme (D. P. Barr and S. D. Aust, 1994, Arch. Biochem. Biophys. 312, 511-515). In this work, we investigated protective mechanisms for manganese peroxidase. Oxidation of Mn(II) by manganese peroxidase displayed complex kinetics, which were explained by accumulation of compound III followed by its reactivation by the enzymatically produced Mn(III). Conversion of compound III to ferric enzyme by Mn(III) was not observed for lignin peroxidase or heme propionate-modified recombinant manganese peroxidase, suggesting that Mn(III) may interact with compound III of native manganese peroxidase at a heme propionate to oxidize iron-coordinated superoxide via long-range electron transfer. Additionally, Mn(II) also reactivated compound III. Although this reaction was slower, it could prevent compound III accumulation when excess Mn(II) was present. Another protective mechanism for manganese peroxidase is proposed for insufficient chelator conditions. In contrast to effective Mn(II) chelators, low-affinity ligands supported considerably slower enzyme turnover, and Mn(III) released was more reactive with hydrogen peroxide, resulting in a catalase-type reaction. Reactivation of compound III and catalatic activity may provide biologically relevant mechanisms for protection of manganese peroxidase against suicidal inactivation by hydrogen peroxide under a variety of manganese and oxalate conditions.

Basidiomycota↗
PubMed1989

Molecular cloning, nucleotide sequence, and abscisic acid induction of a suberization-associated highly anionic peroxidase.

A highly anionic peroxidase induced in suberizing cells was suggested to be the key enzyme involved in polymerization of phenolic monomers to generate the aromatic matrix of suberin. The enzyme encoded by a potato cDNA was found to be highly homologous to the anionic peroxidase induced in suberizing tomato fruit. A tomato genomic library was screened using the potato anionic peroxidase cDNA and one genomic clone was isolated that contained two tandemly oriented anionic peroxidase genes. These genes were sequenced and were 96% and 87% identical to the mRNA for potato anionic peroxidase. Both genes consist of three exons with the relative positions of their two introns being conserved between the two genes. Primer extension analysis showed that only one of the genes is expressed in the periderm of 3 day wound-healed tomato fruits. Southern blot analyses suggested that there are two copies each of the two highly homologous genes per haploid genome in both potato and tomato. Abscisic acid (ABA) induced the accumulation of the anionic peroxidase transcripts in potato and tomato callus tissues. Northern blots showed that peroxidase mRNA was detectable at 2 days and was maximal at 8 days after transfer of potato callus to solid agar media containing 10(-4) M ABA. The transcripts induced by ABA in both potato and tomato callus were identical in size to those induced in wound-healing potato tuber and tomato fruit. The anionic peroxidase peptide was detected in extracts of potato callus grown on the ABA-containing media by western blot analysis. The results support the suggestion that stimulation of suberization by ABA involves the induction of the highly anionic peroxidase.

Abscisic Acid↗
PubMed2002

Degradation of chlorophenols by Phanerochaete chrysosporium: effect of 3,4-dichlorophenol on extracellular peroxidase activities.

Extracellular peroxidases play an important role in the degradation of chlorophenols by Phanerochaete chrysosporium. Depending on the moment of 3,4-dichlorophenol addition, the production of lignin peroxidase and manganese peroxidase in C-limited agitated cultures was affected in opposite ways. In cultures that received 3,4-dichlorophenol at the time of inoculation, fungal growth was reduced and peroxidases were not produced, whereas peroxidase activities were stabilized after 3,4-dichlorophenol addition to pregrown cultures. Further investigation revealed that mRNA encoding lignin peroxidase was not produced in cultures started with 3,4-dichlorophenol, suggesting that the onset of secondary metabolism was affected. In addition, the stabilization of lignin peroxidase activity was not the result of an activation of lignin peroxidase gene transcription, as shown by Northern blot experiments, but likely due to the inhibition of peroxidase degradation by extracellular proteases.

Biodegradation, Environmental↗
PubMed1998

Use of azo dye ligand chromatography for the partial purification of a novel extracellular peroxidase from Streptomyces viridosporus T7A.

Crude peroxidase preparations from the lignocellulose-degrading actinomycete, Streptomyces viridosporus T7A, were shown to decolorize several azo dye isomers and showed a correlation of dye structure to degradability similar to that shown by fungal Mn-peroxidase, an enzyme not previously described in actinomycetes. Addition of the heme-peroxidase inhibitor KCN did not significantly change the ability of the T7A enzyme(s) to decompose the dyes. These results suggest that T7A may produce an Mn- or other peroxidase with similar substrate specificity to Mn-peroxidase. Affinity chromatography using immobilized azo dye isomers was used for purifying peroxidases from T7A. A significantly purified peroxidase preparation was obtained irrespective of the azo dye used. In comparison, concanavalin A lectin affinity chromatography showed very poor binding and resolution for T7A peroxidases. Azo dye affinity purification gave preparations sufficiently purified to allow amino acid microsequencing for two of the bound proteins. N-terminal amino acid sequences were found to share significant homology with a fungal Mn-peroxidase and actinomycete cellulases.

Amino Acid Sequence↗
PubMed2006

Peroxidase activity in soybeans following inoculation with Phytophthora sojae.

The effects of race-specific resistance as conditioned by Rps genes (rps, Rps1-k, Rps2, Rps3, Rps6) in two genetic backgrounds (Williams & Harosoy) on accumulation of soluble peroxidases were determined by a soybean peroxidase capture assay (SPCA) after inoculation with P. sojae races 2, 7, or 25. Peroxidase activity increased in all isolines during the 72 h after inoculation, but reactions varied depending on time after inoculation, genetic background, Rps gene and P. sojae race. Peroxidase activity was higher in race-specific resistant than in susceptible reactions at 72 h. after inoculation, except for plants with the Rps2 gene which confers a unique form of root resistance in addition to the whole plant race-specific resistance. Williams isolines had larger increases in peroxidase activity than Harosoy isolines when data were averaged across Rps genes, and was most evident when plants were inoculated with race 2. When soybeans were inoculated with race 7 Rps1-k resistant plants had the highest increase in peroxidase activity, but Rps2 susceptible plants had a significantly higher peroxidase activity than plants with rps, Rps3, and Rps6 that were also susceptible. Results from inoculations with race 25 were somewhat different, Rps2 resistant plants had the highest increase in peroxidase activity; however, plants with the Rps3 or Rps6 gene that were also resistant did not have a significantly higher peroxidase activity than susceptible plants with the rps or Rps1-k gene.

Peroxidases↗
PubMed1990

Lignin peroxidase H2 from Phanerochaete chrysosporium: purification, characterization and stability to temperature and pH.

The wood-destroying fungus Phanerochaete chrysosporium secretes extracellular enzymes known as lignin peroxidases that are involved in the biodegradation of lignin and a number of environmental pollutants. Several lignin peroxidases are produced in liquid cultures of this fungus. However, only lignin peroxidase isozyme H8 has been extensively characterized. In agitated nutrient nitrogen-limited culture, P. chrysosporium produces two lignin peroxidases in about equal proportions. The molecular weights of these two major proteins (H2 and H8) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 38,500 (H2) and 42,000 (H8). The isoelectric points of these enzymes were 4.3 for H2 and 3.65 for H8. All subsequent experiments in this study were performed with H2 as it contributed the most (42%) to total activity and had the highest specific activity (57.3 U/mg). The Km values of lignin peroxidase H2 for H2O2 and veratryl alcohol were calculated to be 47 microM and 167 microM at pH 3.5, respectively. The pH optima for veratryl alcohol oxidase activity were pH 2.5 at 25 degrees C, pH 3.0 at 35 degrees C, and pH 3.5 at 45 degrees C. In the same manner the temperature optimum shifted from 25 degrees C at pH 2.5 to 45 degrees C at pH 3.5 and approximately 45-60 degrees C at pH 4.5. During storage the resting enzyme was relatively stable for 48 h up to 50 degrees C. Above this temperature the enzyme lost all activity within 6 h at 60 degrees C. At 70 degrees C all activity was lost within 10 min. The resting enzyme retained approximately 80% of its initial activity when stored at 40 degrees C for 21 h at a pH range of 4.0-6.5. Above pH 7.5 and below 4.0, the enzyme lost all activity in less than 5 h. During turnover the enzyme remained active at pH 5.5 for over 2 h whereas the enzyme activity was lost after 45 min at pH 2.5. The oxidation of veratryl alcohol was inhibited by EDTA, azide, cyanide, and by the catalase inhibitor 3-amino-1,2,4-triazole, but not by chloride. In the absence of another reducing substrate incubation of lignin peroxidase H2 with excess H2O2 resulted in partial and irreversible inactivation of the enzyme. The spectral characteristics of lignin peroxidase H2 are similar to those of other peroxidases. The suitability of lignin peroxidases for industrial applications is discussed.

Benzyl Alcohols↗
PubMed1983

Histochemical distribution of peroxidase in ascidians with special reference to the endostyle and the branchial sac.

The histochemical distribution of peroxidase was studied in 10 species of ascidians. In the endostyle, strong peroxidase activity was found in zone 7 in Ciona intestinalis, Ascidia zara, Ascidia sydneiensis samea, Cnemidocarpa areolata, Styela clava, and Pyrura vittata. The activity in zone 7 was weak in Styela plicata and Halocynthia hilgendorfi. Pyura michaelseni and Halocynthia roretzi showed only faint activity in zone 7, but showed strong activity in zone 9 and in the transitional zone, respectively. Pyura vittata exhibited peroxidase activity in zone 5 as well as in zone 7. Zone 8 was negative for peroxidase, but the cilia of zone 8 cells were distinctly stained for peroxidase in Ciona intestinalis and Cnemidocarpa areolata. These results show that wide species differences exist in the distribution of peroxidase in the ascidian endostyle. Peroxidase activity was also detected in the branchial sac, although here again wide species differences were noted in terms of peroxidase-positive sites. Peroxidase activity was also found in the postpharyngeal alimentary canal, but not in the tunic.

Animals↗
PubMed1992

Comparison of structure and activities of peroxidases from Coprinus cinereus, Coprinus macrorhizus and Arthromyces ramosus.

Initial structural and kinetic data suggested that peroxidases from Coprinus cinereus, Coprinus macrorhizus and Arthromyces ramosus were similar. Therefore they were characterized more fully. The three peroxidases were purified to RZ 2.5 and showed immunochemical identity as well as an identical M(r) of 38,000, pI about 3.5 and similar amino acid compositions. The N-termini were blocked for amino acid sequencing. The peroxidases had similar retention volumes by anion-exchange and gel-filtration chromatography. All peroxidases showed multiple peaks by Concanavalin A-Sepharose chromatography. The Concanavalin A-Sepharose profiles were different and depended furthermore on a fermentation batch. Tryptic peptide maps were very similar except for one peptide. This peptide contained an N-linked glycan composed of varying ratios of glucosamine and mannose for the three peroxidases. Rate constants and their pH dependence were the same for the three peroxidases using guaiacol or iodide as reducing substrates. We conclude that peroxidases from Coprinus cinereus, Coprinus macrorhizus and Arthromyces ramosus are most likely identical in their amino acid sequences, but deviate in glycosylation which, apparently, has no influence on the reaction rates of the enzyme. We suggest, that the Coprinus fungi express one peroxidase only in contrast to the lignin-degrading white-rot Basidiomycetes, which produce multiple peroxidase isozymes.

Amino Acid Sequence↗
PubMed1993

Glutathione peroxidase, glial cells and Parkinson's disease.

Hyperoxidation phenomena are suspected to be involved in dopaminergic cell death in Parkinson's disease, which affects preferentially the neuromelanin-containing dopaminergic neurons of the substantia nigra. Glutathione peroxidase is the major protective enzyme against hydrogen peroxide toxicity. The distribution of glutathione peroxidase-containing cells was investigated by immunohistochemistry in the midbrain of four control subjects and four patients with Parkinson's disease. (1) Glutathione peroxidase-like immunoreactivity was detected exclusively in glial cells. (2) In control brains, the density of glutathione peroxidase-positive cells was higher in the vicinity of the dopaminergic cell groups known to be resistant to the pathological process of Parkinson's disease. (3) In Parkinson's disease, an increased density of glutathione peroxidase-immunostained cells was observed, surrounding the surviving dopaminergic neurons. The increase in glutathione peroxidase-containing cells was correlated with the severity in dopaminergic cell loss in the respective cell groups. The data suggest that in control brains, a low density of glutathione peroxidase-positive cells surround the dopaminergic neurons the most vulnerable to Parkinson's disease, and that in parkinsonian brains, the increased number of glutathione peroxidase-positive cells may contribute to protect neurons against pathological death. Thus, the amount of glutathione peroxidase protein-containing cells may be critical for a protective effect against oxidative stress, although it cannot be excluded that the level of the enzyme activity remains the crucial factor.

Aged↗
PubMed2005

Purification and characterization of a cationic peroxidase Cs in Raphanus sativus.

A short distance migrating cationic peroxidase from Korean radish seeds (Raphanus sativus) was detected. Cationic peroxidase Cs was purified to apparent homogeneity and characterized. The molecular mass of the purified cationic peroxidase Cs was estimated to be about 44 kDa on SDS-PAGE. After reconstitution of apoperoxidase Cs with protohemin, the absorption spectra revealed a new peak in the Soret region around 400 nm, which is typical in a classical type III peroxidase family. The optimum pH of peroxidase activity for o-dianisidine oxidation was observed at pH 7.0. Kinetic studies revealed that the reconstituted cationic peroxidase Cs has Km values of 1.18 mM and of 1.27 mM for o-dianisidine and H2O2, respectively. The cationic peroxidase Cs showed the peroxidase activities for native substrates, such as coumaric acid, ferulic acid, and scopoletin. This result suggested that cationic peroxidase Cs plays an important role in plant cell wall formation during seed germination.

Gene Expression Regulation, Developmental↗