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At least 721 records · Page 40Linked to original sources
PubMed1990

The fine structural localization of endogenous and exogenous peroxidase activity in human bone marrow mast cells under pathological conditions.

We have examined the ultrastructural characteristics of peroxidase activity in human bone marrow mast cells. These studies were performed in three patients with systemic mast cell disease, and in another six patients showing bone marrow mast cell hyperplasia. Endogenous peroxidase activity was localized in the perinuclear cisternae and strands of endoplasmic reticulum, but never in the granules. We have also demonstrated the "in vivo" existence of exogenous peroxidase activity in two of the three cases of systemic mast cell disease. The peroxidase internalization involved its binding to the plasma membrane, followed by its incorporation into the cell by a general endocytic process comprising the uptake of dispersed peroxidase-positive material mainly by phagocytosis of granular structures containing peroxidase. The exogenous peroxidase appeared in non-membrane bound granules, vacuoles or aggregates, but we have never seen the enzyme linked to the mast cell granules.

Adult↗
PubMed2003

The peroxidase gene family in plants: a phylogenetic overview.

The 73 class III peroxidase genes in Arabidopsis thaliana were used for surveying the evolutionary relationships among peroxidases in the plant kingdom. In Arabidopsis, the 73 genes were clustered in robust similarity groups. Comparison to peroxidases from other angiosperms showed that the diversity observed in Arabidopsis preceded the radiation of dicots, whereas some clusters were absent from grasses. Grasses contained some unique peroxidase clusters not seen in dicot plants. We found peroxidases in other major groups of land plants but not in algae. This might indicate that the class III peroxidase gene family appeared with the colonization of land by plants. The present survey may be used as a rational basis for further investigating the functional roles of class III peroxidases.

Arabidopsis↗
PubMed2004

Effect of pH on the stability of Pleurotus eryngii versatile peroxidase during heterologous production in Emericella nidulans.

Complementary DNA (cDNA) encoding the new versatile peroxidase from the ligninolytic basidiomycete Pleurotus eryngii has been expressed in the ascomycete Emericella nidulans. In recombinant E. nidulans cultures, the pH reached values as high as 8.3, correlating with a sharp decrease in peroxidase activity. Peroxidase was rapidly inactivated at alkaline pH, but was comparatively stable at acidic pH. The peroxidase inactivation in alkaline buffer could be reversed by adding Ca(2+) and lowering the pH. However, reactivation did not result after incubating the enzyme in non-buffered E. nidulans cultures that reached pH 7.5. To optimize recombinant peroxidase production, the effect of controlling the pH in E. nidulans bioreactor cultures was studied. An extended growth period, and a significant increase in the recombinant peroxidase level (5.3-fold higher activity than in the bioreactor without pH control) was obtained when the pH was maintained at 6.8, showing that culture pH is an important parameter for recombinant peroxidase production.

Bioreactors↗
PubMed2003

Salicylic acid changes the properties of extracellular peroxidase activity secreted from wounded wheat (Triticum aestivum L.) roots.

Wheat ( Triticum aestivum L.) roots released proteins showing peroxidase activity in the apoplastic solution in response to wound stress. Preincubation of excised roots with 1 mM salicylic acid at pH 7.0 enhanced the guaiacol peroxidase activity of the extracellular solution (so-called extracellular peroxidase). The soluble enzymes were partially purified by precipitation with ammonium sulfate followed by size exclusion and ion exchange chromatography. Despite an increase in the total activity of secreted peroxidase induced by pretreatment of excised roots with salicylic acid, the specific activity of the partially purified protein was significantly lower compared to that of the control. Purification of the corresponding proteins by ion exchange chromatography indicates that several isoforms of peroxidase occurred in both control and salicylic acid-treated samples. The activities of the extracellular peroxidases secreted by the salicylic acid-treated roots responded differently to calcium and lectins compared with those from untreated roots. Taken together, our data suggest that salicylic acid changes the isoforms of peroxidase secreted by wounded wheat roots.

Adaptation, Physiological↗
PubMed2003

Cyclometalated ruthenium(II) complexes as efficient redox mediators in peroxidase catalysis.

Cyclometalated ruthenium(II) complexes, [Ru(II)(C~N)(N~N)(2)]PF(6) [HC~N=2-phenylpyridine (Hphpy) or 2-(4'-tolyl)pyridine; N~N=2,2'-bipyridine, 1,10-phenanthroline, or 4,4'-dimethyl-2,2'-bipyridine], are rapidly oxidized by H(2)O(2) catalyzed by plant peroxidases to the corresponding Ru(III) species. The commercial isoenzyme C of horseradish peroxidase (HRP-C) and two recently purified peroxidases from sweet potato (SPP) and royal palm tree (RPTP) have been used. The most favorable conditions for the oxidation have been evaluated by varying the pH, buffer, and H(2)O(2) concentrations and the apparent second-order rate constants ( k(app)) have been measured. All the complexes studied are oxidized by HRP-C at similar rates and the rate constants k(app) are identical to those known for the best substrates of HRP-C (10(6)-10(7) M(-1) s(-1)). Both cationic (HRP-C) and anionic (SPP and RPTP) peroxidases show similar catalytic efficiency in the oxidation of the Ru(II) complexes. The mediating capacity of the complexes has been evaluated using the SPP-catalyzed co-oxidation of [Ru(II)(phpy)(bpy)(2)]PF(6) and catechol as a poor peroxidase substrate as an example. The rate of enzyme-catalyzed oxidation of catechol increases more than 10000-fold in the presence of the ruthenium complex. A simple routine for calculating the rate constant k(c) for the oxidation of catechol by the Ru(III) complex generated enzymatically from [Ru(II)(phpy)(bpy)(2)](+) is proposed. It is based on the accepted mechanism of peroxidase catalysis and involves spectrophotometric measurements of the limiting Ru(II) concentration at different concentrations of catechol. The calculated k(c) value of 0.75 M(-1) s(-1) shows that the cyclometalated Ru(II) complexes are efficient mediators in peroxidase catalysis.

Animals↗
PubMed2003

Down-regulation of an anionic peroxidase in transgenic aspen and its effect on lignin characteristics.

It is generally accepted that peroxidases catalyze the final step in the biosynthesis of lignin. In this study, to examine how expression of prxA3a, a gene for an anionic peroxidase, might be related to lignification in plant tissues, we produced transgenic tobacco plants that harbored a gene for beta-glucuronidase (GUS) fused to the prxA3a promoter. Histochemical staining for GUS activity indicated that the prxA3a promoter was active mainly in the lignifying cells of stem tissues. Further, to examine the effects of suppressing the expression of prxA3a, we transferred an antisense prxA3a gene construct into the original host, hybrid aspen ( Populus sieboldii x P. gradidentata), under the control of the original promoter of the prxA3a gene. Eleven transformed aspens were obtained and characterized, and the stable integration of the antisense construct was confirmed by PCR and Southern blotting analysis in all these lines. Assays of enzymatic activity showed that both total peroxidase activity and acidic peroxidase activity were lower in most transgenic lines than in the control plants. In addition, the reduction of peroxidase activity was associated with lower lignin content and modified lignin composition. Transgenic lines with the highest reduction of peroxidase activity displayed a higher syringyl/vanillin (S/V) ratio and a lower S+V yield, mainly because of a decreased amount of V units. Thus, our results indicate that prxA3a is involved in the lignification of xylem tissue and that the down-regulation of anionic peroxidase alters both lignin content and composition in hybrid aspen.

Down-Regulation↗
PubMed1986

Specific assays for peroxidases in human saliva.

The peroxidase activity in human whole saliva is due to salivary peroxidase and, in some cases, myeloperoxidase; it is usually determined by spectrophotometric methods based on the rate of oxidation of chromogen substrates. Thiocyanate ion, a normal component of saliva, interferes with these kinetic assays by competing with the chromogen for the available oxidizing equivalents; this results in underestimation of peroxidase activity. Both salivary peroxidase and myeloperoxidase will catalyse the peroxidation of the thiocyanate ion; the product, hypothiocyanite ion, is a reactive oxidizing agent. We have developed an assay for total peroxidase activity in saliva, based on the rate of formation of hypothiocyanite, which is not affected by the concentrations of thiocyanate found in saliva. Myeloperoxidase will catalyse the peroxidation of the chloride ion but salivary peroxidase will not; the product of this in neutral solution is the hypochlorite ion, which is also a reactive oxidizing agent. The specific contribution was determined of myeloperoxidase to total peroxidase activity in saliva by measuring the rate of both hypochlorite and hypothiocyanite formation. Because the thiocyanate ion will compete with the chloride ion, the concentration of thiocyanate in saliva samples must be reduced below 0.05 mM prior to measurements of the rate of hypochlorite formation.

Humans↗
PubMed1983

Changes in the electrophoretic pattern of salivary peroxidase at the middle of the menstrual cycle.

Salivary peroxidase activity is known to increase at the middle of the menstrual cycle, and we report changes in electrophoretic patterns of salivary peroxidase over the same period. Peroxidase during the early follicular and late luteal phases of the menstrual cycle has been resolved into three forms by polyacrylamide gel electrophoresis. An additional, low mobility peroxidase has been detected at midcycle when two electrophoretic forms occurring at other times are reduced; this is coincident with the peak in total peroxidase activity. Available evidence suggests that this ovulatory peroxidase represents a catalytically active aggregate of the peroxidases normally present in saliva.

Electrophoresis, Polyacrylamide Gel↗
PubMed1988

A simple two-step immunocytochemical method using protein A-peroxidase to stain immunoreactive cell antigens.

We report a simple two-step immunocytochemical method that uses staphylococcal protein A conjugated to horseradish peroxidase and the H2O2-3,3'-diaminobenzidine chromogenic reaction to stain neurons and fibers containing immunoreactive cell antigens. Our protein A-peroxidase method was found to produce stains of equal or superior quality to those of the classical 3-step peroxidase-anti-peroxidase (PAP) technique. Since the chromogenic reaction with protein A-peroxidase has low non-specific tissue binding, the reaction can be carried out at acidic pH with higher horseradish peroxidase activity and no significant increase in background. Using this method, we were able to produce clear stains of neurons and fibers containing tyrosine hydroxylase or fibers containing methionine-enkephalin. The use of protein A-peroxidase conjugate substantially simplified the immunocytochemistry procedure, and reduced both the time and cost of experiments.

Animals↗
PubMed1983

Histochemical distribution of peroxidase in amphioxus and cyclostomes with special reference to the endostyle.

The histochemical distribution of peroxidase was studied in amphioxus, ammocoetes larvae, adult lampreys, and hagfish. The endostyle of amphioxus displayed peroxidase activity in zone 5 and, in some individuals, in zone 1 as well. The endostyle of ammocoetes exhibited strong peroxidase activity in type 2c and type 3 cells. These peroxidase-positive regions coincide well with radioiodine-binding regions previously described. Thyroid follicles of adult lampreys stained strongly for peroxidase, but those of the hagfish did not. The branchial sac of amphioxus showed peroxidase activity, but the gill sac of cyclostomes did not. The intestine did not show peroxidase activity in amphioxus or in cyclostomes.

Animals↗
PubMed1983

Non-proteolytic solubilization of bovine thyroid peroxidase: thermodynamic parameters of the thermoinactivation.

1. A subcellular fractionation from bovine thyroid gland homogenate was carried out by differential centrifugation. The maximal peroxidase activity was found in the microsomal fraction. 2. The effect of non-proteolytic agents on the solubilization of the enzyme was studied. It was found that non-ionic detergents with Hydrophilic Lipophilic Balance (HLB) between 12 and 14, such as Triton X-100 and Brij 96, were the best solubilizing agents. 3. The effect of pH, ionic strength, time and temperature of incubation of the peroxidase solubilization was analyzed. 4. The thermodynamic parameters of the thermoinactivation of solubilized enzyme and the activation energy (Ea) of the peroxidase-catalyzed reaction were calculated. 5. The values obtained for these parameters were very similar to those of the plant peroxidases, suggesting a common catalytic mechanism, as Bardsley et al., Eur. J. Biochem. (1982) have pointed out. 6. However thyroid peroxidase does not undergo any reactivation as plant peroxidases do, due to the role of the hydrophobic interactions which hold the peroxidase bound to microsomal membranes in the thyroid glands.

Animals↗
PubMed1975

Differentiation of two abnormalities in thyroid peroxidase causing organification defect and goitrous hypothyroidism.

Clinical and laboratory evaluations are reported on two patients with congenital goiter and hypothyroidism due to iodide organification defect. In one patient, a 31-year-old white male with severe mental retardation, administration of perchlorate caused discharge of 69% of the radioiodine accumulated in the thyroid gland. Thyroid tissue had negligible peroxidase activity in the tyrosine-iodinase, triliodide, and guaiacol assays. Preincubation of subcellular fractions with hematin restored activity. The restored enzyme was labile to high concentrations of H2O2 (5.6times 10-4 h2o2 produced inhibition in the triiodide assay). Heating of the enzyme for 5 min at 46 degrees C produced 50% inactivation, while higher temperatures were required to half-inactivate normal peroxidases. This case represents a second example of the "peroxidase apoenzyme-prosthetic group defect" causing congenital goiter. The second patient, an example of the "deficient peroxidase defect," was a 10-yr-old girl with 35% discharge of thyroidal radioiodine by perchlorate. Peroxidase activity in the goiter tissue was quantitatively decreased (10%-20% of normal values) but kinetically normal with respect to apparent Km for H2O2. Hematin had little effect on the enzyme. Peroxidase activity had abnormal subcellular distribution, since pellets sedimenting between 39,000 and 105,000 g contained most of the activity. Normal thyroglobulin was observed in the thyroid gland of the patient. Two distinct defects of the peroxidase system can produce congenital goiter by limiting organification of iodide.

Adult↗
PubMed1985

Ultrastructural peroxidase cytochemistry of three established human myelogenous leukemia cell lines, HL-60, KG-1 and ML-2.

We studied the ultrastructural peroxidase cytochemistry of three established human acute myelogenous leukemia cell lines (HL-60, KG-1 and ML-2) to clarify the cytochemical differences and the differences in maturation/differentiation stages. HL-60 cells contained azurophil granules which exhibited strong peroxidase reaction. The more central region of individual granules is less reactive than the outer portion of these granules. The secretory apparatus of HL-60 cells, i.e. rough endoplasmic reticulum, perinuclear cisterna and Golgi apparatus, also contained peroxidase-reactive material. ML-2 cells contained azurophil granules with peroxidase reaction; however, nuclear membranes were peroxidase-negative and thin cisternae of rough endoplasmic reticulum exhibited only a faint peroxidase reaction. KG-1 cells were peroxidase-negative. From these findings KG-1 is classified as the least mature of the cell lines studied. ML-2 cells are considered early promyelocytes and HL-60 cells as late promyelocytes.

Cell Differentiation↗
PubMed1988

Electron paramagnetic resonance spectroscopy of thyroid peroxidase.

Thyroid peroxidase was isolated from porcine thyroids by two methods. Limited trypsin proteolysis was employed to obtain a cleaved enzyme, and affinity chromatography was used to isolate intact thyroid peroxidase. Enzyme isolated by both methods was used in the examination of the heme site of native thyroid peroxidase and its complexes by EPR spectroscopy. Intact thyroid peroxidase showed a homogeneous high-spin EPR signal with axial symmetry, in contrast to the rhombic EPR signal of native lactoperoxidase. Reaction of cyanide or azide ion with native thyroid peroxidase resulted in the loss of the axial EPR signal within several hours. The EPR spectroscopy of the nitrosyl adduct of ferrous thyroid peroxidase exhibited a three-line hyperfine splitting pattern and indicated that the heme-ligand structure of thyroid peroxidase is significantly different from that of lactoperoxidase.

Animals↗
PubMed1993

Inhibition of intestinal peroxidase activity by nonsteroidal antiinflammatory drugs.

The peroxidase activity of the mitochondrial fraction of rat intestine is inhibited in vitro by non-steroidal antiinflammatory drugs (NSAIDs), such as indomethacin (IMN) and acetylsalicylic acid (ASA), the former being more potent than the latter. The peroxidase was solubilised by cetab-NH4Cl extraction and purified to apparent homogeneity by Sephadex G-150 gel filtration and affinity chromatography on Con-A Sepharose. The purified enzyme activity was 80% inhibited by 150 microM IMN and 50% by 2.67 mM ASA. IMN could also inhibit lactoperoxidase activity to the same extent but not the horseradish peroxidase activity. The inhibition of peroxidase-catalysed iodide oxidation by IMN and ASA was optimal at pH 5.5 and 4.5, respectively. Kinetic studies revealed that the inhibition by IMN was competitive with respect to iodide or guaiacol, while the inhibition by ASA was noncompetitive and reversible in nature. Studies of some structural analogues showed that indole-3-acetic acid was as effective as IMN, while salicylic acid was more potent than ASA. Spectral studies showed a small bathochromic shift of the Soret band of the enzyme by IMN, suggesting its possible interaction at or near the heme moiety. The competitive nature of IMN may be explained as due to its oxidation by the peroxidase to a product absorbing at 412 nm, the formation of which is inhibited by iodide. We suggest that IMN inhibits intestinal peroxidase activity by acting as a competitive substrate for the enzyme. As intestinal peroxidase is mainly contributed by the invading eosinophils, NSAIDs may affect the host defence mechanism by inhibiting the activity of the enzyme.

Animals↗
PubMed1987

Variations among cultured cells in glutathione peroxidase activity in response to selenite supplementation.

The aim of this study was to devise conditions for manipulation of the activity of selenium-dependent glutathione peroxidase in cell lines by means of variation in culture medium contents of selenite and fetal calf serum. Nine different cell lines were studied. A low glutathione peroxidase activity was, in most cases, obtained by the use of a medium with a low (2%) serum content. Selenite induced in most of the cell lines an increase in glutathione peroxidase activity, with a plateau ranging from 10 nM to 300-1000 nM. Growth-retarding effects of selenite became apparent at 300-2000 nM, showing a large cell line variation. Supplementation with 50-100 nM selenite for 1 week should generally be suitable for maximal glutathione peroxidase induction. The selenium contents of serum batches were highly variable, pointing to the importance of using only one well-defined, preferably low-selenium, batch. The glutathione peroxidase activities varied considerably between cell lines and the selenite-induced increases ranged from negligible to more than 10-fold. The availability of cell lines with such variable responses should be valuable for experiments aimed at evaluating the importance of glutathione peroxidase and selenium compounds independently of glutathione peroxidase for the protection against oxidative insult.

Cell Division↗
PubMed1993

Lignin-degrading peroxidases of Phanerochaete chrysosporium.

Lignin and manganese peroxidases are secreted by the basidiomycete Phanerochaete chrysosporium during secondary metabolism. These enzymes play major roles in lignin degradation. The active site amino acid sequence of these lignin-degrading peroxidases is similar to that of horseradish peroxidase (HRP) and cytochrome c peroxidase (CcP). The mechanism by which they oxidize substrates also appears to be the similar. pH has a similar effect on lignin peroxidase compound I formation as on HRP or CcP; however, the pKa controlling compound I formation for lignin peroxidase appears to be much lower. Lignin-degrading peroxidases are able to catalyze the oxidation of substrates with high redox potential. This unique ability is consistent with a heme active site of low electron density, which is indicated by high redox potential.

Amino Acid Sequence↗
PubMed1996

Involvement of peroxidase in chorion hardening in Aedes aegypti.

Peroxidase activity is detectable in Aedes aegypti ovaries, containing developing eggs, at 24 h following blood feeding, and peak peroxidase activity is reached at 36-48 h after the blood-meal. Peroxidase is associated with the chorion layer in mature eggs and the majority of the enzyme is released from the chorion layer by treating the isolated chorion fraction with SDS/urea. Analysis of the SDS/urea solubilized chorion proteins using SDS-PAGE with tropolone/H2O2 or dopa staining verified the presence of both peroxidase and phenol oxidase in the released chorion proteins. The molecular weight of chorion peroxidase is about 61,000 Da as determined by SDS-PAGE analysis. Incubation of the solubilized chorion proteins with tyrosine and H2O2 produces dityrosine, and hyrolysis of hardened egg chorion results in the detection of dityrosine and trityrosine in the chorion hydrolysate. Data suggest that chorion peroxidase is involved in the hardening of the mosquito egg chorion by catalyzing the formation of ditryrosine through tyrosine residues on structural proteins. The overall hardening of the A. aegypti egg chorion includes both peroxidase-mediated chorion protein crosslinking through dityrosine formation and phenol oxidase-catalyzed chorion melanization.

Aedes↗