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PubMed1977

Effects of selenium and vitamin E on blood selenium levels, tissue glutathione peroxidase activities and white muscle disease in sheep fed purified or hay diets.

The effects of selenium and vitamin E on blood selenium levels and tissue glutathione peroxidase activities were determined in sheep fed purified and hay diets. A significant increase of blood levels of this element and tissue glutathione peroxidase activities was found in sheep given selenium as compared to those not receiving this element. Of the tissues examined, the highest glutathione peroxidase activity was found in the heart. Vitamin E had no influence on either the blood selenium levels or upon the tissue glutathione peroxidase activity. With hydrogen peroxide as the substrate, tissue glutathione peroxidase activity was not correlated with the incidence of white muscle disease. Evidence is presented to suggest that 0.1 ppm dietary selenium is not sufficient under some conditions to meet the physiological requirements for this element.

Animal Feed↗
PubMed1983

Platelet glutathione peroxidase activity as an index of selenium status in rats.

Glutathione peroxidase activity in platelets increased stepwise in selenium-depleted rats that were repleted with graded levels of dietary sodium selenite. In a 3-phase depletion/repletion/depletion feeding study, glutathione peroxidase activity was similar in platelets and liver, which apparently contains the largest labile pool of selenium in the body. The activity of glutathione S-transferase (selenium-independent glutathione peroxidase) in platelets was low and was not affected by selenium deficiency, even though hepatic transferase was markedly elevated in selenium-deficient rats. Vitamin E deficiency did not affect activities of glutathione peroxidase or glutathione S-transferase in platelets or liver. Determination of glutathione peroxidase activity in platelets apparently is a promising technique for assessing selenium status and, possibly, for measuring selenium bioavailability.

Animals↗
PubMed1993

Modelling of the lignin peroxidase LIII of Phlebia radiata: use of a sequence template generated from a 3-D structure.

A model of the lignin peroxidase LIII of Phlebia radiata was constructed on the basis of the structure of cytochrome c peroxidase (CCP). Because of the low percentage of amino acid identity between the CCP and the lignin peroxidase LIII of Phlebia radiata, alignment of the sequences was based on the generation of a template from a knowledge of the 3-D structure of CCP and consensus sequences of lignin peroxidases. This approach gave an alignment in which all the insertions in the lignin peroxidase were placed at loop regions of CCP, with a 21.1% identity for these two proteins. The model was constructed using this alignment and the computer program COMPOSER, which assembles the model as a series of rigid fragments derived from CCP and other proteins. Manual intervention was required for some of the longer loop regions. The alpha-helices forming the structural framework, and especially the haem environment of CCP, are conserved in the LIII model and the core is close packed without holes. A possible site of the substrate oxidation at the haem edge of LIII is discussed.

Amino Acid Sequence↗
PubMed1985

Neutrophil mean peroxidase: a biologically interesting parameter with a potential for WBC differential quality control.

This study has shown the neutrophil mean peroxidase measurement on the Technicon H6000 to be a simple reproducible technique for measuring neutrophil myeloperoxidase. This measurement shows no interference from contaminating eosinophils unlike spectrophotometric methods. The WBC count had little effect on the CV of the neutrophil mean peroxidase within the normal working range of the machine. Variations in the hydrogen peroxide concentration of the peroxidase substrate also had little effect on this measurement. Haemoglobin however had a significant inhibitory effect on the neutrophil mean peroxidase but this was in a predictable manner. The same inhibition of peroxidase also caused a decrease in the eosinophil count. This varied between individuals. The method described represents a suitable assay for the detection of varying degrees of neutrophil myeloperoxidase activity including the acquired and hereditary deficiencies. This parameter is potentially useful for the quality control of the cytochemically derived WBC differential.

Autoanalysis↗
PubMed1986

Purification, characterization and origin of rat gastric peroxidase.

A membrane-bound peroxidase (EC 1.11.1.7) from rat stomach has been solubilized by 0.2% cetyltrimethylammonium bromide in the presence of 1.2 M NH4Cl. The enzyme was purified 3355-fold to apparent homogeneity as judged by acid polyacrylamide gel electrophoresis and appears to be a cationic protein. In sodium dodecyl sulfate gel electrophoresis, the enzyme shows single polypeptide band of Mr 45,000. In gel permeation, the Mr has been estimated as 47,000. Spectral properties indicate the presence of Soret band at 412 nm which shifts to 425 nm on complexation with CN- and to 430 nm on reduction with dithionite. The velocity constant, k1 for the reaction of the peroxidase with H2O2 is 1.38 X 10(7) M-1 s-1 and Km for H2O2 is 0.1 mM. The enzyme contains active sulphydryl groups and is inhibited by sulphydryl reagents of which p-hydroxymercuribenzoate is more reactive than mersalyl or N-ethylmaleimide. The enzyme is very resistant to thermal denaturation up to 65 degrees C and also to chaotropic reagents at least up to 2 M above which it is inactivated. The enzyme shows similarity with the intestinal eosinophil peroxidase as regards the molecular mass, spectral, kinetic and some of the catalytic properties. However, they differ significantly in terms of their interaction with fluoride ion, sulphydryl reagents, chaotropic reagent and also with the antiserum against the gastric peroxidase. Histochemically, the gastric peroxidase is shown to be localised in the gastric gland proper of the fundic stomach, rich in parietal and chief cells.

Animals↗
PubMed1990

Two-dimensional 1H-NMR studies of horseradish peroxidase C and its interaction with indole-3-propionic acid.

The binding of aromatic donor molecules to plant peroxidases has been investigated by examining the complex formed between horseradish peroxidase isoenzyme C and indole-3-propionic acid using two-dimensional 1H-NMR spectroscopy. Despite the relatively high molecular mass and paramagnetism of the protein, this technique can be successfully applied to provide new information on the structure of the complex. A number of relatively well-resolved resonances in certain regions of the one-dimensional spectrum are assigned to amino acid type on the basis of the two-dimensional experiments. Two phenylalanine side chains are found to interact at positions close to the haem group as shown by nuclear Overhauser effect spectroscopy (NOESY). Furthermore, the NOESY spectrum of the complex reveals distinct interactions between these phenylalanine residues and the indole ring of the donor molecule. The binding site is found to comprise of these phenylalanine side chains and also the methyl group of a leucine or valine residue. On the basis of the model structure of horseradish peroxidase isoenzyme C proposed by Welinder and Nørskov-Lauritsen and information from previous studies of the related turnip peroxidases, possible locations for this binding site are discussed. The NMR methods adopted here may be generally applicable to the study of peroxidase--aromatic-donor interactions.

Amino Acid Sequence↗
PubMed1977

Protein A-peroxidase: a valluable tool for the localization of antigens.

Protein A of Staphylococcus aureus has been conjugated to horseradish peroxidase and used in an indirect immunolabeling technique to visualize membrane and viral antigens. The same Protein A-peroxidase conjugate was used with antisera from five different species. Using this indirect test, membrane markers for T and B lymphocytes were labeled with a greater specificity than when peroxidase conjugated anti-immunoglobulin was used in the second step. Viral antigens on cells infected with measles, vesicular stomatitis, herpes or visna virus, respectively, were also stained in the protein A-peroxidase indirect test with a greater specificity than indirect method using anti-immunoglobulin. Paired preparations were examined in the light and electron microscope. Ultrastructural analysis showed that the protein A-peroxidase conjugate penetrated well through fixed viral membranes and resulted in fine resolution of antigenic sites.

Animals↗
PubMedDate not supplied

Degradation of textile dyes mediated by plant peroxidases.

The peroxidase enzyme from the plants Ipomea palmata (1.003 IU/g of leaf) and Saccharum spontaneum (3.6 IU/g of leaf) can be used as an alternative to the commercial source of horseradish and soybean peroxidase enzyme for the decolorization of textile dyes, mainly azo dyes. Eight textiles dyes currently used by the industry and seven other dyes were selected for decolorization studies at 25-200 mg/L levels using these plant enzymes. The enzymes were purified prior to use by ammonium sulfate precipitation, and ion exchange and gel permeation chromatographic techniques. Peroxidase of S. spontaneum leaf (specific activity of 0.23 IU/mg) could completely degrade Supranol Green and Procion Green HE-4BD (100%) dyes within 1 h, whereas Direct Blue, Procion Brilliant Blue H-7G and Chrysoidine were degraded >70% in 1 h. Peroxidase of Ipomea (I. palmata leaf; specific activity of 0.827 U/mg) degraded 50 mg/L of the dyes Methyl Orange (26%), Crystal Violet (36%), and Supranol Green (68%) in 2-4 h and Brilliant Green (54%), Direct Blue (15%), and Chrysoidine (44%) at the 25 mg/L level in 1 to 2 h of treatment. The Saccharum peroxidase was immobilized on a hydrophobic matrix. Four textile dyes, Procion Navy Blue HER, Procion Brilliant Blue H-7G, Procion Green HE-4BD, and Supranol Green, at an initial concentration of 50 mg/L were completely degraded within 8 h by the enzyme immobilized on the modified polyethylene matrix. The immobilized enzyme was used in a batch reactor for the degradation of Procion Green HE-4BD and the reusability was studied for 15 cycles, and the half-life was found to be 60 h.

Azo Compounds↗
PubMed2006

Oxidation capacity of laccases and peroxidases as reflected in experiments with methoxy-substituted benzyl alcohols.

A set of methoxy-substituted benzyl alcohol (MBA) congeners were examined regarding susceptibility to oxidation by Trametes versicolor laccase, T. versicolor lignin peroxidase and horseradish peroxidase: 2,4,5-trimethoxybenzyl alcohol (TMBA), 3,4,5-TMBA, 2,3,4-TMBA, 2,5-dimethoxybenzyl alcohol (DMBA), 3,4-DMBA, and 2,3-DMBA. The corresponding methoxy-substituted benzaldehydes were strongly predominant as products on enzymic oxidation. This together with different reaction rates and redox potentials makes the MBAs suitable as substrates in the characterization of ligninolytic enzymes. For fungal laccase, the reaction rate order was: 2,4,5-TMBA >> 2,5-DMBA > 3,4-DMBA > 3,4,5-TMBA approximately 2,3,4-TMBA approximately 2,3-DMBA. Horseradish peroxidase displayed a similar reactivity order. Oxidation of some of the MBAs with laccase and horseradish peroxidase was only observed when the reactions were carried out at low pH and with relatively high-substrate concentration. 3,4-DMBA (veratryl alcohol) was the best substrate for lignin peroxidase and the reaction rate order was: 3,4-DMBA > 2,4,5-TMBA approximately 3,4,5-TMBA > 2,5-DMBA > 2,3,4-TMBA approximately 2,3-DMBA. The oxidation experiments with different MBAs elucidate the potential of the enzymes as oxidants in various applications.

Basidiomycota↗
PubMed1981

Comparison of chromogens for the determination of horseradish peroxidase as a marker in enzyme immunoassay.

o-Phenylenediamine, 2,2'-azino-di(3-ethylbenzthiazoline sulphonic acid-6) (ABTS), o-dianisidine and 4-aminoantipyrine were compared as chromogens for the determination of horseradish peroxidase. Highest sensitivity in the determination of horseradish peroxidase-IgG conjugates in dissolved form was obtained with o-phenylenediamine. When these conjugates were used in a two-site binding enzyme immunoassay for hepatitis B surface antigen (HBsAg), the steepest calibration curve and the lowest detection limit were obtained when ABTS was used to determine the immune complexes bound to the solid phase. Non-ionic detergents, such as polyoxyethylene-sorbitol ester, retarded horseradish peroxidase inactivation, resulting in a chromogen-dependent activity rise of horseradish peroxidase. An optimised determination of horseradish peroxidase is reported, in which the sensitivity of the solid phase enzyme immunoassay is doubled by the use of o-dianisidine.

Ampyrone↗
PubMed1976

[Catalytic properties and stability of horseradish peroxidase immobilized in polyacrylamide gel].

Effect of polyacrylamide (PAA) gel on properties of horseradish peroxidase, immobilized by means of the incorporation into PAA gel is studied. Catalytic properties of immobilized enzyme are studied. Km value and pH-dependency of the enzyme activity are found to be close to those of soluble enzyme, kcat value is 3 times lower at pH 7.0. PH-stability of immobilized peroxidase at 20 degrees C and thermostability of soluble and immobilized peroxidases at pH 7.0 within the temperature range from 20 to 81 degrees C are studied. The stability of peroxidase in PAA gel is found to decrease (in 3 times at 20 degrees C, and in 17 times at 56 degrees C). A mechanism of the effect of PAA gel on catalytic properties and stability of peroxidase is discussed.

Acrylamides↗
PubMed1979

Studies on the conjugation of horseradish peroxidase to immunoglobulin G via glutaraldehyde.

Horseradish peroxidase was conjugated to immunoglobulin G via glutaraldehyde by a two-step procedure using an increasing excess of peroxidase in the second step reaction. The yield of conjugated monomeric IgG and the amount of free IgG were analyzed by SDS-polyacrylamide electrophoresis and gel-filtration. The antigen binding capacity of the enzyme-antibody conjugates was evaluated by radial immunodiffusion. Conjugation of peroxidase to IgG with a 1:20 molar:molar excess of glutaraldehyde-activated peroxidase resulted in a high yield of conjugated IgG without any detectable amounts of polymers of IgG or residual free IgG. The antigen binding capacity of the conjugate varied between different antigen-antibody systems, but in general it was not significantly different from that of native IgG. The enzyme activity was reduced to 70% of the activity of native peroxidase.

Aldehydes↗
PubMed1975

Effect of cadmium chloride on the rat testicular soluble selenoenzyme, glutathione peroxidase.

Thirty-six hours after male rats were injected with 25 mumoles cadmium chloride/ml/kg of body weight they exhibited decreased plasma and testicular glutathione (GSH) peroxidase activity, testicular atrophy and necrosis, and increased testicular thiobarbituric acid-reactive products. Seven days after injection, only the plasma GSH peroxidase activity returned to normal. The decrease in testicular GSH peroxidase activity was not reversible by dialysis against buffer or by the addition of selenium as buffered selenomethionine. In vitro inhibition of testicular GSH peroxidase activity occurred at 0.3 mM cadmium. All in vivo effects were prevented by a prior injection of 25 mumoles sodium selenite/ml/kg of body weight. Testicular GSH peroxidase may be the direct or indirect target of cadmium-induced testicular damage, and this damage results in lipid peroxidation.

Animals↗
PubMed1978

[Chemical modification of epsilon-amino lysine groups in horseradish peroxidase. Its effect on catalytic properties and spatial structure of the enzyme].

Effect of chemical modification of horseradish peroxidase lysine epsilon-amino groups by propionic, butyric, valeric, succinic anhydrides and trinitrobenzolsulfonic acid (TNBS) on catalytic properties of the enzyme is investigated. All the preparations of modified peroxidase have 100% peroxidase activity for o-dianizidine at pH 7.0, which indicates the absence of lysine epsilon-amino group in the enzyme active site. pH-dependencies of modified peroxidase relative activity are studied; modification by anhydrides of monobasic acids is not found to result in changes of the relative activity pH-profile, while modification by succinic anhydride widens it. Absorption and circular dichoism spectra of native and modified peroxidase within 260--270 nm are obtained, some changes in the enzyme tertiary structure after its epsilon-amino groups modification are observed. Modification of four epsilon-amino groups by buturic and succinic anhydrides and of three epsilon-amino groups by TNBS is found to increase the regidity of protein surrounding of heme, and modification of six epsilon-amino groups by TNBS results in more unwrapped enzyme structure as compared with its native molecule.

Butyrates↗
PubMed1986

Peroxidase activity in the mouse uterus, placenta and fetus during pregnancy.

Changes in peroxidase activity during pregnancy were examined in CD-1 mice. Peroxidase activity was measured with guaiacol as the substrate in uterine extracts of nonpregnant mice and in uterine, placental, and fetal extracts of pregnant mice on days 9, 12, 14, 16, and 18 of gestation. Uterine peroxidase activity in nonpregnant mice was high, but declined logarithmically to only 0.2% by day 18 of pregnancy. In contrast to this decline, a concomitant 50-fold logarithmic increase in fetal peroxidase activity was observed between day 12 and 18. Activity in placental extracts did not change significantly throughout the gestational period examined. These results suggest that membrane bound peroxidase in mouse uterus and fetus undergoes major shifts during pregnancy.

Animals↗
PubMed1986

Enhancement of cardioplegic protection with the free-radical scavenger peroxidase.

This study assesses the ability of the free-radical scavenger peroxidase to enhance cardioplegic protection when given during or before myocardial ischemia. Forty-four isolated isovolumetric buffer-perfused rat hearts were studied. In a first series of experiments that consisted of three groups, hearts were subjected to 90 min of normothermic global ischemia followed by 45 min of reperfusion. One group received a crystalloid cardioplegic solution given as a single dose at the onset of arrest. A second group received cardioplegic solution supplemented with superoxide dismutase (200,000 U/liter), and a third group received cardioplegic solution supplemented with peroxidase (6000 U/liter). Based on comparisons of postreperfusion coronary flow, left ventricular developed pressure, maximum dP/dt, and diastolic pressure, we found that the best protection was provided by peroxidase-enriched cardioplegia. A second series of experiments was then undertaken to assess the effects of the latter enzyme given as a pretreatment. Hearts were subjected to 3 hr of global ischemia, during which myocardial protection was provided by hypothermia (15 degrees C) along with multidose cardioplegia. The treatment group was given peroxidase (10,000 U/liter) added to the perfusate fluid for 15 min before the onset of cardioplegic arrest without further enzyme supplementation during ischemia or reperfusion. Hearts perfused with standard buffer for an equal period of time served as controls. While the two groups demonstrated the same degree of postischemic increase in myocardial stiffness, peroxidase-pretreated hearts had a significantly better recovery of contractile indexes at 30 and 45 min of reflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Contribution of protein conformation to stereochemistry and reactivity of the active center of heme proteins and enzymes. The existence of horseradish peroxidase conformations and their possible role in the catalysis mechanism].

In the spectral region 350-800 nm at 4.2 K we measured magnetic circular dichroism (MCD) spectra of the pentacoordinated complex of protcheme with 2-methylimidazole, deoxyleghemoglobin, neutral and alkaline forms of reduced horseradish peroxidase in the equilibrium states, as well as in non-equilibrium states produced by low-temperature photolysis of their carbon monoxide derivatives. Earlier the corresponding results have been obtained for myoglobin, hemoglobin and cytochromes P-450 and P-420. The energies of Fe-N (proximal His) and Fe-N(pyrroles) bonds and their changes upon ligand binding in heme proteins and enzymes were compared with those in the model heme complex thus providing conformational contribution into stereochemistry of the active site. The examples of weak and strong conformational "pressure" on stereochemistry were analysed and observed. If conformational energy contribution into stereochemistry prevails the electronic one the heme stereochemistry remains unchanged on ligand binding as it was observed for leghemoglobin and alkaline horseradish peroxidase. The change of bond energies in myoglobin and hemoglobin on ligand binding are comparable with those in protein free pentacoordinated protoheme, giving an example of weak conformational contribution to heme stereochemistry. The role of protein conformation energy in the modulation of ligand binding properties of heme in leghemoglobin relative to those in myoglobins is discussed. The most striking result were obtained in the study of reduced horseradish peroxidase in the pH region of 6.0-10.2. It was found that such different perturbations as ligand binding and heme-linked ionization of the distal amino acid residue induce identical changes in heme stereochemistry. Neither heme-linked ionization in the carbon monoxide complex nor the geometry of Fe-Co bond affect the heme local structure of photoproducts. These and other findings suggest a very low conformation mobility of horseradish peroxidase whose protein constraints appear to allow only two preferable geometries of specific amino acid residues that form the heme pocket. The role of the two tertiary structure constraints on the heme in the mechanism of horseradish peroxidase function is discussed. It is supposed that one conformation produces a heme environment suitable for two-electron oxidation of the native enzyme to compound I by hydrogen peroxide while another conformation changes the heme stereochemistry in the direction favourable for back reduction of compound I by the substrate to the resting enzyme through two one-electron steps. The switch from one tertiary structure to another is expected to be induced by substrate bind

Binding Sites↗
PubMed1985

Heme-linked ionization of horseradish peroxidase compound II monitored by the resonance Raman Fe(IV)=O stretching vibration.

Fe(IV)=O resonance Raman stretching vibrations were recently identified by this laboratory for horseradish peroxidase compound II and ferryl myoglobin. In the present report it is shown that Fe(IV)=O stretching frequency for horseradish peroxidase compound II will switch between two values depending on pH, with pKa values corresponding to the previously reported compound II heme-linked ionizations of pKa = 6.9 for isoenzyme A-2 and pKa = 8.5 for isoenzyme C. Similar pH-dependent shifts of the Fe(IV)=O frequency of ferryl myoglobin were not detected above pH 6. The Fe(IV)=O stretching frequencies of compound II of the horseradish peroxidase isoenzymes at pH values above the transition points were at a high value approaching the Fe(IV)=O stretching frequency of ferryl myoglobin. Below the transition points the horseradish peroxidase frequencies were found to be 10 cm-1 lower. Frequencies of the Fe(IV)=O stretching vibrations of horseradish peroxidase compound II for one set of isoenzymes were found to be sensitive to deuterium exchange below the transition point but not above. These results were interpreted to be indicative of an alkaline deprotonation of a distal amino acid group, probably histidine, which is hydrogen bonded to the oxyferryl group below the transition point. Deprotonation of this group at pH values above the pKa disrupts hydrogen bonding, raising the Fe(IV)=O stretching frequency, and is proposed to account for the lowering of compound II reactivity at alkaline pH. The high value of the Fe(IV)=O vibration of compound II above the transition point appears to be identical in frequency to what is believed to be the Fe(IV)=O vibration of compound X.

Deuterium↗