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At least 1,423 records · Page 79Linked to original sources
PubMed1983

Microwave effects on immobilized peroxidase chemiluminescence.

Protein gels formed by crosslinking bovine serum albumin and horseradish peroxidase with glutaraldehyde were used to measure effects on peroxidase activity of 400-MHz (CW) radiofrequency radiation (RFR) at an average specific absorption rate (SAR) of 1.45 W/kg. The enzyme activity was measured by luminol chemiluminescence recorded on photographic film after hydrogen peroxide activation. Activity was measured during RFR exposure of gels or after exposure of gels polymerized in the RFR field. During exposure, a significant (P less than .05) reversible increase occurred in overall mean peroxidase activity of gels activated with 0.88 M H2O2 but not in those activated with 8.8 M H2O2. Gels containing solubilized luminol and formed in the field showed no overall mean increase in peroxidase activity, but did display a highly significant (P less than .001) alteration in the distribution of local activities when compared to unexposed gels. These results are apparently due to changes in the rate of diffusion (concentration equilibration) of hydrogen peroxide in the gel.

Enzymes, Immobilized↗
PubMedDate not supplied

Interaction of metals with peroxidase--mediated luminol-enhanced, chemiluminescence (PLmCL).

The peroxidase-mediated luminol-enhanced chemiluminescence (PLmCL) method has been used to study the in vitro effect of contaminants such as heavy metals on the reactive oxygen species production by immunocytes. We were interested to know whether metals could directly affect peroxidase-mediated luminescence, taking horseradish peroxidase (HRP) as a model enzyme, since this could contribute to the inhibition of immunocyte LmCL. Copper inhibited PLmCL in a dose-dependent manner, while cadmium, iron, silver and lead only partly decreased the signal in the concentration range tested. In contrast, zinc enhanced the signal at high concentrations. Eventually, chromium, mercury and aluminium did not affect PLmCL. It is suggested that these effects reflect the ability of the metals to interact with the active site of the peroxidase. These results demonstrate that such interactions have to be considered when interpreting the effects of metals on immunocytes using the LmCL method.

Animals↗
PubMed2002

Redox intermediates of plant and mammalian peroxidases: a comparative transient-kinetic study of their reactivity toward indole derivatives.

A comparative study on the reactivity of five indole derivatives (tryptamine, N-acetyltryptamine, tryptophan, melatonin, and serotonin), with the redox intermediates compound I (k2) and compound II (k3) of the plant enzyme horseradish peroxidase (HRP) and the two mammalian enzymes lactoperoxidase (LPO) and myeloperoxidase (MPO), was performed using the sequential-mixing stopped-flow technique. The calculated bimolecular rate constants (k2, k3) revealed substantial differences regarding the oxidazibility of the substrates by redox intermediates at pH 7.0 and 25 degrees C. With HRP it was shown that k2 and k3 are mainly determined by the reduction potential (Eo') of the substrate with k2 being 7-45 times higher than k3. Compound I of mammalian peroxidases was a much better oxidant than HRP compound I with the consequence that the influence of the indole structure on k2 of LPO and MPO was small varying by a factor of only 88 and 38, respectively, which is in strong contrast to a factor of 160,000 determined for k2 of HRP. Interestingly, the k3 values for all three enzymes were very similar. Oxidation of substrates by mammalian peroxidase compound II is strongly constrained by the nature of the substrate. The k3 values for the five indoles varied by a factor of 3,570 (LPO) and 200,000 (MPO), suggesting that the reduction potential of compound II of mammalian peroxidase is less positive than that of compound I, which is in contrast to the plant enzyme.

Animals↗
PubMed1993

Peroxidase-catalyzed desulfonation of 3,5-dimethyl-4-hydroxy and 3,5-dimethyl-4-aminobenzenesulfonic acids.

Horseradish peroxidase (HRP), lignin peroxidase (LiP), and Mn(III)-malonate (a manganese peroxidase mimic) oxidized 3,5-dimethyl-4-hydroxybenzenesulfonic acid (I) to 2,6-dimethyl-1,4-benzoquinone (III) and 2,6-dimethyl-1,3,4-trihydroxybenzene (IV). Only LiP was efficient at oxidizing 3,5-dimethyl-4-aminobenzenesulfonic acid (II); LiP oxidized II to 2,6-dimethyl-1,4-benzoquinone (III) and 2,6-dimethyl-3-hydroxy-1,4-benzoquinone (V). In these reactions, the H2O2-oxidized peroxidases or Mn(III)-malonate oxidized the aromatic ring by two electrons to produce a cation. Nucleophilic attack by water on the sulfonic acid bearing carbon eliminated sulfonic acid as inorganic sulfite and produced 2,6-dimethyl-1,4-benzoquinone (III). Possible mechanisms for the formation of IV and V are discussed.

Basidiomycota↗
PubMed1994

Effect of heme-apoprotein interactions on the activity of horseradish and wheat germ peroxidases.

The apoenzymes of horseradish and wheat germ peroxidases were reconstituted with synthetic hemins that differ from natural heme in the substitution pattern of side chains. Both enzymes show dual peroxidase and oxygenase activity, being the latter the oxidation of porphobilinogen in the presence of oxygen and a reducing agent. The oxygenase activity was almost unaffected in both enzymes reconstituted with synthetic hemes, while peroxidase activities were inhibited to different extents. According to the pattern of activity inhibition it was concluded that there is low flexibility of both apoproteins in the regions of the acid side chain contact which could be a general features of peroxidases.

Apoenzymes↗
PubMed1992

Cloning and sequencing of a cDNA encoding ascorbate peroxidase from Arabidopsis thaliana.

A cDNA clone encoding ascorbate peroxidase (AP, EC 1.11.1.11) was isolated from a phage lambda gt11 library of cDNA from Arabidopsis thaliana by immunoscreening with monoclonal antibodies against the enzyme, and then sequenced. The cDNA insert hybridized to a 1.1 kb poly(A)+ RNA from leaves of A. thaliana. Genomic hybridization suggests that the cDNA obtained here corresponds to a single-copy gene. The N-terminal amino acid sequence of Arabidopsis AP was determined by protein sequencing of the immunochemically purified enzyme, and proved to be homologous to the N-terminal amino acid sequence of the chloroplastic AP of spinach. The predicted amino acid sequence of the mature AP of A. thaliana, deduced from the nucleotide sequence, consists of 249 amino acid residues, which is 34% homologous with cytochrome c peroxidase of yeast, but less homologous with other plant peroxidases. Amino acid residues at the active site of yeast cytochrome c peroxidase are conserved in the amino acid sequence of Arabidopsis AP. The poly(dG-dT) sequence, which is a potential Z-DNA-forming sequence, was found in the 3' untranslated region of the cDNA.

Amino Acid Sequence↗
PubMed1984

Lysosomes in skeletal muscle following denervation. Time course of horseradish peroxidase uptake and increase of lysosomal enzymes.

The in-vivo uptake of exogenously applied horseradish peroxidase and the activities of the lysosomal enzymes acid phosphatase and cathepsin D were studied histochemically and/or biochemically in innervated and 2-14 day-denervated tibialis anterior muscles of the mouse. The biochemically determined uptake of horseradish peroxidase showed a large increase already 4 days after denervation. The activities of the lysosomal enzymes increased in a more gradual fashion, and only cathepsin D showed an increase in activity when expressed as total activity per muscle. Histochemically horseradish peroxidase was found to be localized in muscle fibres in characteristic spindle-shaped segments after denervation. The main increase in the number of such segments per transverse section of the muscle occurred between 3 and 6 days after denervation. In serial sections these segments frequently showed positive staining also for acid phosphatase. It is concluded that exogenously applied horseradish peroxidase is taken up into the lysosomal system, which after denervation becomes organized into characteristic spindle-shaped segments in the muscle fibres. The endocytic activity of muscle fibres increases early after denervation. This is followed by a more gradual increase in activity of lysosomal enzymes and finally by an organization of the lysosomal system into characteristic spindle-shaped segments. The results are compatible with the working hypothesis that increased endocytosis may initiate lysosomal activation in denervated skeletal muscle.

Acid Phosphatase↗
PubMed1986

Salivary peroxidases.

Peroxidases are known to be involved in the intracellular metabolism of H2O2 coupled with various physiological functions. Apart from the thyroid gland, the enzyme has been isolated from various extrathyroidal sources of which salivary gland is one of the richest sources of the enzyme. The enzyme from bovine and goat submaxillary gland has been extensively studied in terms of their molecular, spectral, kinetic, catalytic and immunological properties and compared with the lactoperoxidase which is similar to the salivary peroxidase. The modulation of the salivary peroxidase by various factors and the probable mechanism of the modulation has been described. The enzyme has also been compared with the thyroid peroxidase as regards their physicochemical properties as well as on the immunological and functional aspects. The similarities and dissimilarities have been incorporated. The possible function of the enzyme in iodine metabolism and in bactericidal action has been discussed.

Animals↗
PubMed1977

The blood-brain barrier to horseradish peroxidase under normal and experimental conditions.

This review paper deals with the transport of the protein tracer horseradish peroxidase across cerebral vessels under normal and various experimental conditions. Electronmicroscopical investigations have revealed that, under normal conditions, a minor vesicular transfer of intravenously injected peroxidase occurs across the endothelium in segments of arterioles, capillaries and venules, especially in arterioles with a diameter about 15-30 mu. This normally occurring vesicular transport is susceptible to various experimental conditions. Thus the transfer of tracer increases when a hypertonic solution is injected into the internal carotid artery presumably due to vesicular transport. Extensive acute hypertension of short duration also increases the vesicular transfer of peroxidase from blood to brain. Identical observations are obtained when the hypertension is evoked by intravenous injection of phentolamine and by electrically induced seizures. During the postischemic period, one hour after release of the occlusion of an internal carotid artery in the Mongolian gerbil the vesicular transport of peroxidase is increased across the endothelium of cerebral vessels. The explanation may be release of serotonin from blood platelets during the occlusion. The serotonin could then increase the blood pressure locally in the brain resulting in an enhanced permeability. Serotonin, after perfusion through the cerebral ventricular system, is also able to increase the normally occurring vesicular transfer. The most likely mechanism behind this phenomenon seems at the moment to be local hypertension evoked by serotonin-induced vasoconstriction of arterioles. Finally, the enhanced vesicular transport across cerebral endothelium caused by porto-caval anastomosis is mentioned and the possible role of disturbances in the metabolism of amines as responsible for the extravasation is discussed.

Animals↗
PubMed1981

Comparison between biochemical and histochemical assessments of peroxidase activity in rat mammary tumours.

The endogenous peroxidase content of 26 'hormone-dependent' and 16 'hormone-independent' rat mammary tumours was assessed by means of a biochemical (guaiacol) assay on tumour extracts and by means of a histochemical (diaminobenzidine) technique on frozen sections of the same tumours. By guaiacol assay, the hormone-dependent tumours had significantly higher peroxidase levels than the hormone-independent tumours. In contrast, by diaminobenzidine staining of the same tumours, peroxidase was detectable in 94% of hormone-independent tumours but in only 54% of hormone-dependent tumours. Moreover, there was no direct correlation between the results of biochemical and histochemical methods. At least in these rat mammary tumours, therefore, histochemical estimates of peroxidase activity based on the diaminobenzidine reaction do not seem to reflect the same tissue properties as biochemical estimates based on the guaiacol reaction after tissue disruption.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Identical populations of phagocytes and dying neurons revealed by intravascularly injected horseradish peroxidase, and by endogenous glutaraldehyde-resistant acid phosphatase, in the brains of chick embryos.

Intravascularly injected horseradish peroxidase selectively labels certain classes of cells in the brains of chick embryos: phagocytes, which have characteristic distributions and resemble either gitter cells or microglia; and some, but not all, dying neurons. Healthy neurons are not labelled. If the isthmo-optic nucleus is caused to degenerate by an intraocular injection of colchicine on the opposite side, most of its neurons take up peroxidase. However, destroying the afferents to the isthmo-optic nucleus increases its loss of neurons without affecting the number labelled. In sections double-reacted for horseradish peroxidase and endogenous acid phosphatase, all, and indeed only, the peroxidase-labelled cells exhibit intense, clumped acid phosphatase activity which resists glutaraldehyde fixation. This is true of all cell types in both normal and operated embryos. Even healthy neurons exhibit acid phosphatase activity, but this can be distinguished, because it is largely inhibited by fixation with glutaraldehyde.

Acid Phosphatase↗
PubMed1984

NALL-1, an acute lymphoblastic leukemia cell line with peroxidase activity.

All cells examined from the non-B, non-T acute lymphoblastic leukemia cell line, NALL-1, stained positive both for terminal deoxynucleotidyl transferase and for common ALL antigen. In addition, peroxidase activity was detected by light microscopy in 55 to 75% of cells and peroxidase-positive granules were detected ultrastructurally in greater than 80% of cells. Peroxidase activity in NALL-1 may result from derepression of peroxidase genes or clonal proliferation of a biphenotypic precursor cell.

Adolescent↗
PubMedDate not supplied

Selenium-containing peroxidases of germinating barley.

Germinating barley grown on an artificial medium was exposed to 75Se-selenite for 8 d. Then the leaves were homogenized and proteins were separated by means of Sephadex G-150 filtration, followed by DEAE-Sepharose chromatography. Each fraction collected was assayed for total protein, radioactivity, and peroxidase activity. In barley leaves, three protein peaks (peaks no. I, II, and III) with peroxidase activity could be separated by Sephadex G 150 filtration. Each fraction was then further separated on DEAE-Sepharose chromatography. Thus, peaks I and II were resolved by DEAE-Sepharose into one major and two minor peaks of radioactivity. However, only the major peak showed peroxidase activity. Peak III was resolved from the gel filtration on the DEAE-sepharose into one major and four minor peaks of radioactivity. The major and three of the minor radioactivity peaks contained peroxidase activity. The protein fractions were separated by polyacrylamide gel electrophoresis. The molecular weights of separated proteins were estimated by means of molecular markers, and 75Se radioactivity was evaluated by autoradiography. Thus, gel filtration peak I contained four bands with mol wts of 128, 116, 100, and 89 kDa. Of these, the 89 kDa protein contained selenium. Peak II contained three protein bands with mol wts 79.4, 59.6, and 59.9. The 59.6 band was a selenoprotein. Peak III contained four protein bands (and some very weak bands). The four major bands had mol wts of 38.6, 31.6, 30.2, and 29.2 kDa. The last mentioned band was a selenoprotein.

Animals↗
PubMed2006

Redox properties of the Fe3+/Fe2+ couple in Arthromyces ramosus class II peroxidase and its cyanide adduct.

The thermodynamics of the one-electron reduction of the ferric heme in free and cyanide-bound Arthromyces ramosus peroxidase (ARP), a class II plant peroxidase, were determined through spectro-electrochemical experiments. The data were compared with those for class III horseradish peroxidase C (HRP) and its cyanide adduct, and were interpreted in terms of ligand binding features, electrostatic effects and solvent accessible surface area of the heme group and of catalytically relevant residues in the heme distal site. The E(o)' values for free and cyanide-bound ARP (-0.183 and -0.390 V, respectively, at 25 degrees C and pH 7) are higher than those for HRP and HRP-CN. ARP features an enthalpic stabilization of the ferrous state and a remarkably negative reduction entropy, which are both unprecedented for heme peroxidases. Once the compensatory contributions of solvent reorganization are partitioned from the measured reduction enthalpy, the resulting protein-based deltaH(o)'(rc(int)) value for ARP turns out to be less positive than that for HRP by +10 kJ mol(-1). The smaller stabilization of the oxidized heme in ARP most probably results from the less pronounced anionic character of the proximal histidine, and the decreased polarity in the heme distal site as compared with HRP, as indicated by the X-ray structures. The surprisingly negative deltaS(o)'(rc) value for ARP is the result of peculiar reduction-induced solvent reorganization effects.

Crystallography, X-Ray↗
PubMed1984

Sedimentation equilibrium studies on the interaction between cytochrome c and cytochrome c peroxidase.

The interaction between cytochrome c and cytochrome c peroxidase was investigated using sedimentation equilibrium at pH 6,20 degrees C, in a number of buffer systems varying in ionic strength between 1 and 100 mM. Between 10 and 100 mM ionic strengths, the sedimentation of the individual proteins was essentially ideal, and sedimentation equilibrium experiments on mixtures of the two proteins were analyzed assuming ideal solution behavior. Analysis of the distribution of mixtures of cytochrome c and cytochrome c peroxidase in the ultracentrifuge cell based on a model involving the formation of a 1:1 cytochrome c-cytochrome c peroxidase complex gave values of the equilibrium dissociation constant ranging from 2.3 +/- 2.7 microM at 10 mM ionic strength to infinity (no detectable interaction) at 100 mM ionic strength. Attempts to determine the presence of complexes involving two cytochrome c molecules bound to cytochrome c peroxidase were inconclusive.

Cytochrome c Group↗
PubMed1987

Binding of horse heart cytochrome c to yeast porphyrin cytochrome c peroxidase: a fluorescence quenching study on the ionic strength dependence of the interaction.

The binding of horse heart cytochrome c to yeast cytochrome c peroxidase in which the heme group was replaced by protoporphyrin IX was determined by a fluorescence quenching technique. The association between ferricytochrome c and cytochrome c peroxidase was investigated at pH 6.0 in cacodylate/KNO3 buffers. Ionic strength was varied between 3.5 mM and 1.0 M. No binding occurs at 1.0 M ionic strength although there was a substantial decrease in fluorescence intensity due to the inner filter effect. After correcting for the inner filter effect, significant quenching of porphyrin cytochrome c peroxidase fluorescence by ferricytochrome c was observed at 0.1 M ionic strength and below. The quenching could be described by 1:1 complex formation between the two proteins. Values of the equilibrium dissociation constant determined from the fluorescence quenching data are in excellent agreement with those determined previously for the native enzyme-ferricytochrome c complex at pH 6.0 by difference spectrophotometry (J. E. Erman and L. B. Vitello (1980) J. Biol. Chem. 225, 6224-6227). The binding of both ferri- and ferrocytochrome c to cytochrome c peroxidase was investigated at pH 7.5 as functions of ionic strength in phosphate/KNO3 buffers using the fluorescence quenching technique. The binding in independent of the redox state of cytochrome c between 10 and 20 mM ionic strength, but ferricytochrome c binds with greater affinity at 30 mM ionic strength and above.

Animals↗
PubMed1989

Cytochrome c peroxidase activity of a protease-modified form of cytochrome c-552 from the denitrifying bacterium Pseudomonas perfectomarina.

Protease activity present in aerobically grown cells of Pseudomonas perfectomarina, protease apparently copurified with cytochrome c-552, and trypsin achieved a limited proteolysis of the diheme cytochrome c-552. That partial lysis conferred cytochrome c peroxidase activity upon cytochrome c-552. The removal of a 4000-Da peptide explains the structural changes in the cytochrome c-552 molecule that resulted in the appearance of both cytochrome c peroxidase activity (with optimum activity at pH 8.6) and a high-spin heme iron. The oxidized form of the modified cytochrome c-552 bound cyanide to the high-spin ferric heme with a rate constant of (2.1 +/- 0.1) X 10(3) M-1 s-1. The dissociation constant was 11.2 microM. Whereas the intact cytochrome c-552 molecule can be half-reduced by ascorbate, the cytochrome c peroxidase was not reducible by ascorbate, NADH, ferrocyanide, or reduced azurin. Dithionite reduced the intact protein completely but only half-reduced the modified form. The apparent second-order rate constant for dithionite reduction was (7.1 +/- 0.1) X 10(2) M-1 s-1 for the intact protein and (2.2 +/- 0.1) X 10(3) M-1 s-1 for the modified form. In contrast with other diheme cytochrome c peroxidases, reduction of the low-spin heme was not necessary to permit ligand binding by the high-spin heme iron.

Amino Acid Sequence↗
PubMed1984

Effects of monoclonal antibodies to bovine and Paracoccus denitrificans cytochromes c on reactions with oxidase, reductase and peroxidase.

The effects of monoclonal antibodies to bovine and Paracoccus denitrificans cytochromes c (Kuo, L.M. and Davies, H.C. (1983) Mol. Immunol. 20, 827-838) in the reactions of the cytochromes c with cytochrome c oxidase, reductase and peroxidase were studied. Spectrophotometric assays were employed, under conditions where binding of cytochrome c to the enzymes appears to be rate-limiting. Less than stoichiometric amounts of antibodies to P. denitrificans cytochrome c added to the cytochrome rendered some of it nonoxidizable or nonreducible by the P. denitrificans membrane-bound electron transport system and decreased the rate constant with the remaining cytochrome c. The antibodies appear to affect both electron transport reactions (blocking effects) with the oxidase and reductase and binding effects (effects on rate constants) and to distinguish between the two. Different ratios of antibody site to cytochrome c gave different extents of blocking of the reductase as compared with the oxidase reaction. Differences were also apparent in the effect of these antibodies on the reaction of yeast peroxidase and the oxidase with the P. denitrificans cytochrome c. Antibodies to bovine and P. denitrificans cytochromes c had considerably less effect on the reactions of the bovine cytochrome with bovine oxidase and reductase. One antibody was inhibitory to the oxidase reaction with bovine cytochrome c, but not to that with the reductase. Also, an antibody which inhibited the oxidase reaction had no effect on the reaction with yeast peroxidase. The data give evidence that the interaction areas on cytochrome c for oxidase and reductase and peroxidase are not identical, although they may be nearby.

Animals↗