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At least 1,261 records · Page 70Linked to original sources
PubMed2000

Characterization of different commercial soybean peroxidase preparations and use of the enzyme for N-demethylation of methyl N-methylanthranilate To produce the food flavor methylanthranilate.

The potential of different peroxidase preparations for the N-demethylation of methyl N-methylanthranilate to produce the food flavor methylanthranilate (MA) was investigated. All tested peroxidase preparations were able to catalyze the N-dealkylation. The tested soybean preparations vary widely with respect to their heme content. Furthermore, the operational stability of purified soybean peroxidase (SP) is at least 25-fold lower than that of horseradish peroxidase and only 5-fold higher than that of microperoxidase 8. Thus, the presence of a large protein chain around a porphyrin cofactor in a peroxidase is, by itself, insufficient to explain the observed differences in operational stability. Despite its relatively low operational stability, SP proved to be the most efficient biocatalyst for the production of MA with high yield and purity, especially observed at the high temperature and low pH values at which SP appeared to be optimally active.

Flavoring Agents↗
PubMed2001

Ethylene production and peroxidase activity in aphid-infested barley.

The purpose of this work was to investigate whether ethylene is involved in the oxidative and defensive responses of barley to the aphids Schizaphis graminum (biotype C) and Rhopalophum padi. The effect of aphid infestation on ethylene production was measured in two barley cultivars (Frontera and Aramir) that differ in their susceptibility to aphids. Ethylene evolution was higher in plants infested for 16 hr than in plants infested for 4 hr in both cultivars. Under aphid infestation, the production of ethylene was higher in cv. Frontera than in Aramir, the more aphid susceptible cultivar. Ethylene production also increases with the degree of infestation. Maximum ethylene evolution was detected after 16 hr when plants were infested with 10 or more aphids. Comparing the two species of aphids, Schizaphis graminum induced more ethylene evolution than Rhopalosiphum padi. Infestation with S. graminum increased hydrogen peroxide content and total soluble peroxidase activity in cv. Frontera, with a maximum level of H2O2 observed after 20 min of infestation and the maximum in soluble peroxidase activity after 30 min of infestation. When noninfested barley seedlings from cv. Frontera were exposed to ethylene, an increase in hydrogen peroxide and in total peroxidase activity was detected at levels similar to those of infested plants from cv. Frontera. When noninfested plants were treated with 40 ppm of ethylene, the maximum levels of H2O2 and soluble peroxidase activity were at 10 and 40 min, respectively. Ethylene also increased the activity of both cell-wall-bound peroxidases types (ionically and covalently bound), comparable with infestation. These results suggest that ethylene is involved in the oxidative responses of barley plants induced by infestation.

Animals↗
PubMed2002

Substrate specificity of african oil palm tree peroxidase.

The optimal conditions for catalysis by the peroxidase isolated from leaves of African oil palm tree (AOPTP) have been determined. The pH optimum for oxidation of the majority of substrates studied in the presence of AOPTP is in the interval of 4.5-5.5. A feature of AOPTP is low pH value (3.0) at which the peroxidase shows its maximal activity toward 2,2;-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS). Increasing the buffer concentration changes the AOPTP activity, the degree of the effect depending upon the chemical structure of the substrate. Under optimal conditions of AOPTP catalysis, the values of second order rate constant characterizing efficiency of enzymatic oxidation of substrates have been calculated. It was shown that among 12 peroxidase substrates studied, ABTS and ferulic acid are the best substrates for AOPTP. The results show that substrate specificities of AOPTP and royal palm tree peroxidase are similar, but different from substrate specificity of other plant peroxidases.

Arecaceae↗
PubMed1998

Cytochrome c oxidase as a proton-pumping peroxidase: reaction cycle and electrogenic mechanism.

Cytochrome oxidase (COX) is considered to integrate in a single enzyme two consecutive mechanistically different redox activities--oxidase and peroxidase--that can be catalyzed elsewhere by separate hemoproteins. From the viewpoint of energy transduction, the enzyme is essentially a proton pumping peroxidase with a built-in auxiliary eu-oxidase module that activates oxygen and prepares in situ H2O2, a thermodynamically efficient but potentially hazardous electron acceptor for the proton pumping peroxidase. The eu-oxidase and peroxidase phases of the catalytic cycle may be performed by different structural states of COX. Resolution of the proton pumping peroxidase activity of COX and identification of individual charge translocation steps inherent in this reaction are discussed, as well as the specific role of the two input proton channels in proton translocation.

Animals↗
PubMed2003

Characterization of antigenic properties of horseradish peroxidase with monoclonal antibodies.

Monoclonal antibodies (mcAbs) specific to alkaline isoenzymes of horseradish peroxidase were used to characterize the antigenic properties of horseradish peroxidase. The results of a competitive binding assay indicated that monoclonal antibodies can be divided into three groups directed against distinct parts of the protein. The interaction of monoclonal antibodies with native and modified horseradish peroxidase showed also three different patterns of reactivity. Antibodies from groups I and II are directed against epitopes which are conformational and formed by tertiary structure elements. Epitopes recognized by these antibodies are sensitive to heme removal or partial denaturation of peroxidase. Antibodies from group III bind specifically with epitopes consisting of primary or secondary structure elements. The antigenic determinants recognized by antibodies from group III PO(1) and 36F(9) were shown to be linear (continuous) and formed by amino acid residues 261-267 and 271-277, respectively, as determined by the peptide scanning method (PEPSCAN). The location of revealed linear antigenic determinants in the molecular structure of peroxidase is analyzed.

Amino Acid Sequence↗
PubMedDate not supplied

Cytochemical detection of endogenous peroxidase in the acinar cells of the hamster submandibular gland.

The presence of endogenous peroxidase activity in the hamster submandibular gland was investigated cytochemically by light and electron microscopy using diaminobenzidine methods. After fixation of tissue with 2% paraformaldehyde-2.5% glutaraldehyde and incubation in a DAB reaction medium containing 0.01% H2O2, the peroxidase reaction product was localized in the nuclear envelope, the cisternae of the endoplasmic reticulum, secretory granules and the Golgi apparatus in both the acinar and granular duct cells of the submandibular gland. This is in contrast to earlier investigators who failed to detect peroxidase activity in acinar cells of the hamster submandibular gland and reported that peroxidase is localized only in the granular duct cells. The discrepancy may be caused by differences in experimental procedures. It is suggested that fixation of tissue with a high concentration of glutaraldehyde and incubation in a DAB reaction medium containing a high concentration of H2O2 inhibits the peroxidase activity of acinar cells in the hamster submandibular gland.

3,3'-Diaminobenzidine↗
PubMed2004

Oxidation of phenolic compounds by peroxidase in the presence of soluble polymers.

The kinetics of Coprinus cinereus peroxidase-catalyzed 1-naphthol, 2-naphthol, and 4-hydroxybiphenyl oxidation was investigated. The initial rates of the naphthols' and 4-hydroxybiphenyl oxidations were linearly dependent on enzyme concentration. The rates depended on substrate concentration and saturated at concentrations above 100 microM of hydrogen peroxide, 25-50 microM of naphthols, and 10 microM of 4-hydroxybiphenyl. At the peroxide concentration 100 microM calculated K(m) and the maximal rate (V(max)) were 74.7 microM and 0.53 microM/sec or 175 microM and 2.0 microM/sec for 1- or 2-naphthol, respectively, and 29.68 microM and 0.42 microM/sec for 4-hydroxybiphenyl. Kinetic measurements of exhaustive naphthol and 4-hydroxybiphenyl oxidation showed that peroxidase is inactivated during the oxidation of the substrates. Different factors and additives, water soluble polymers and albumins (PEG, PEI, PL, BSA, HSA), influenced the initial naphthols and 4-hydroxybiphenyl oxidation rates, peroxidase inactivation rates, and the degree of the substrate conversion. Addition of albumin increased turnover number of naphthols oxidation 1.5-4 times. Light scattering increase was observed when peroxidase-catalyzed oxidation reaction was investigated and suggested that insoluble particles were formed during the process. The addition of polymers, change of concentration and ionic strength of the solution as well as the number of other factors influenced the observed light scattering. The number of particles formed during peroxidase-catalyzed naphthols' and 4-hydroxybiphenyl oxidation and their distribution according to size in the interval 2.5-300 microm were detected by particle counting in solutions.

Albumins↗
PubMed2004

Differential activity of peroxidase isozymes in response to wounding, gypsy moth, and plant hormones in northern red oak (Quercus rubra L.).

We measured total peroxidase activity and the activities of peroxidase isoforms in leaves of red oak (Quercus rubra L.) seedlings exposed to wounding and plant hormones in the greenhouse. Activity of specific peroxidase isoforms was induced differentially by gypsy moth wounding, mechanical wounding, and the wound-associated plant hormone jasmonic acid. Activity of one isoform was enhanced modestly by treatment with salicylate. A study of peroxidase activity in naturally occurring galls elicited on red oak leaves by 12 hymenopteran and dipteran insect species found 16 POD isoforms, 11 of which were differentially induced or suppressed in galls compared with leaves. In both studies, total peroxidase activity as measured spectrophotometrically was not clearly related to activity of these isoforms. These results indicate that red oak seedlings and trees may respond specifically to wounding, particular insects, and plant signals through changes in the activities of individual isozymes.

Animals↗
PubMed1998

Plasma levels of selenium, selenoprotein P and glutathione peroxidase and their correlations to fish intake and serum levels of thyrotropin and thyroid hormones: a study on Latvian fish consumers.

OBJECTIVE: To study the relationships between fish intake and different markers of selenium status and thyroid hormone function. DESIGN: Cross-sectional study. SETTING AND SUBJECTS: Sixty-eight men (age 24-79 years) were recruited among coastal fishermen and inland subjects from Latvia. None of the subjects was on selenium medication or had any known endocrine disease. MAIN OUTCOME MEASURES: Correlations between fish intake, plasma levels of selenium, selenoprotein P, glutathione peroxidase, organic mercury in erythrocytes and TSH in serum. RESULTS: Selenium in plasma ranged from 0.30 to 1.56 micromol/l, selenoprotein P from 0.54 to 2.21 arbitrary units relative to pooled plasma, and glutathione peroxidase from 1.20 to 5.73 mg/l. The number of fish meals per month was correlated with plasma selenium, selenoprotein P and glutathione peroxidase (r = 0.63, r = 0.62 and r = 0.50, respectively; P<0.001). Plasma selenium was correlated with selenoprotein P and glutathione peroxidase (r = 0.88 and r = 0.67, respectively; P < 0.001), and also selenoprotein P and glutathione peroxidase were correlated (r = 0.63, P < 0.001). The mean plasma selenium level in those with a high fish intake (21-50 fish meals/month), was 81% higher than in those with lowest fish intake. TSH in serum was inversely correlated with plasma selenium and selenoprotein P. Thyroid hormone levels were not correlated with plasma selenium, selenoproteins or fish intake. CONCLUSIONS: In this study group, selenium from fish intake had a marked impact on all variables studied on selenium status. No impact of selenium status on T3 and T4 levels was observed. The slightly negative correlation of selenium status with TSH levels might indicate a higher TSH secretion at low selenium status.

Adult↗
PubMed2001

Plant peroxidases: substrate complexes with mechanistic implications.

Plant peroxidases are capable of binding phenolic substrates, and it has been possible to crystallize complexes between horseradish peroxidase C (HRP C) and benzhydroxamic acid. The X-ray structures of the binary HRP C:ferulic acid complex and the ternary HRP C:CN(-):ferulic acid complex to 2.0 and 1.45 A resolution, respectively, have also been solved recently. Ferulic acid is a naturally occurring phenolic compound found in the plant cell wall and it is an in vivo substrate for plant peroxidases. The X-ray structures demonstrate the flexibility of the aromatic-donor-binding site in plant peroxidases and highlight the role of the distal arginine in substrate oxidation and ligand binding. A general mechanism of peroxidase substrate oxidation (compound I-->compound II and compound II-->resting state) can be proposed on the basis of the complexes and a large body of biochemical evidence.

Binding Sites↗
PubMed2001

A new versatile peroxidase from Pleurotus.

Lignin peroxidase (LiP) and manganese peroxidase (MnP) have been investigated in Phanerochaete chrysosporium. A third ligninolytic peroxidase has been described in Pleurotus and Bjerkandera. Two of these versatile peroxidases (VPs) have been cloned, sequenced and characterized. They have high affinity for Mn(2+), hydroquinones and dyes, and also oxidize veratryl alcohol, dimethoxybenzene and lignin dimers. The deduced sequences show higher identity with Ph. chrysosporium LiP than MnP, but the molecular models obtained include a Mn(2+)-binding site. Concerning aromatic substrate oxidation, Pl. eryngii VP shows a putative long-range electron transfer pathway from an exposed trytophan to haem. Mutagenesis and chemical modification of this tryptophan and the acidic residues forming the Mn(2+)-binding site confirmed their role in catalysis. The existence of several substrate oxidation sites is supported further by biochemical evidence. Residue conservation in other fungal peroxidases is discussed.

Binding Sites↗
PubMed1968

A comparison of horseradish peroxidase and manganese ions as catalysts for the oxidation of dihydroxyfumaric acid.

With horseradish peroxidase as catalyst the main product was dihydroxytartrate, but small amounts of glycolaldehyde, mesoxalic semialdehyde, mesoxalate and possibly glyoxal were also formed. Mn(2+) catalysis gave rise only to mesoxalate and oxalate. When oxygen uptake was followed by a manometric method the rate of the peroxidase-catalysed reaction was proportional to oxygen concentration and marked inhibition by cyanide was obtained only at low buffer concentration. The catalytic effects of peroxidase and Mn(2+) were almost always additive. Chelating agents inhibited the Mn(2+)-catalysed reaction, but had either no effect or a slight accelerating effect on the peroxidase-catalysed reaction. It is concluded that Mn(2+) does not function as cofactor in the peroxidase-catalysed oxidation.

Aldehydes↗
PubMed1971

Complex-formation between cytochrome c and cytochrome c peroxidase. Kinetic studies.

1. The kinetics of ferrocytochrome c peroxidation by yeast peroxidase are described. Kinetic differences between the older and more recent preparations of the enzyme most probably arise from differences in intrinsic turnover rates. 2. The time-courses of cytochrome c peroxidation by the enzyme follow essentially first-order kinetics in phosphate buffer. Deviations from first-order kinetics occur in acetate buffer, and are due to a higher enzymic turnover rate in this medium accompanied by a greater tendency to autocatalytic peroxidation of cytochrome c. 3. The kinetics of ferrocytochrome c peroxidation by yeast peroxidase are interpreted in terms of a mechanism postulating formation of reversible complexes between the peroxidase and both reduced and oxidized cytochrome c. Formation of these complexes is inhibited at high ionic strengths and by polycations. 4. Oxidized cytochrome c can act as a competitive inhibitor of ferrocytochrome c peroxidation by peroxidase. The K(i) for ferricytochrome c is approximately equal to the K(m) for ferrocytochrome c and thus probably accounts for the observed apparent first-order kinetics even at saturating concentrations of ferrocytochrome c. 5. The results are discussed in terms of a possible analogy between the oxidations of cytochrome c catalysed by yeast peroxidase and by mammalian cytochrome oxidase.

Acetates↗
PubMed1971

Deiodination of L-thyroxine and its activity on the oxidation in vitro of reduced nicotinamide-adenine dinucleotide by peroxidase plus hydrogen peroxide.

When l-thyroxine activates the oxidation of NADH by peroxidase+H(2)O(2), little removal of phenolic-ring iodine atoms becomes apparent until most of the NADH has been oxidized, after which it increases markedly. This extensive deiodination is accompanied by loss of the ability of thyroxine to catalyse the oxidation of NADH by peroxidase+H(2)O(2). The slight deiodination observed before the appearance of extensive deiodination is somewhat higher when the effect of thyroxine on NADH oxidation is greater, and lower when thyroxine has exerted a slighter effect. ICN (but not I(2) or thyronine) catalyses NADH oxidation, in both the presence and the absence of peroxidase+H(2)O(2): thyroxine+peroxidase+H(2)O(2) are thus comparable with ICN alone in their effects on NADH oxidation. The obvious conclusion from the above observation, namely that the active moiety is the halogen liberated from thyroxine (or ICN) is, however, not directly supported by some of the results obtained by measuring the degree of deiodination of thyroxine in the system. In an attempt to reconcile some apparently contradictory conclusions, it is suggested that, when thyroxine activates oxidation of NADH by peroxidase+H(2)O(2), the diphenyl ether structure is undergoing cyclic deiodination and iodination. This would be accompanied by the maintenance in the reaction medium of an oxidized form of iodine, similar to that liberated by ICN, which would be the actual active moiety, until the NADH concentration becomes so low that the diphenyl ether structure is ruptured oxidatively. An alternative explanation is that thyroxine is oxidized to a form that either oxidizes NADH or loses iodine in competing reactions.

Chemical Phenomena↗
PubMed1982

Studies on mammalian intestinal peroxidase.

A peroxidase, purified from rat small intestine to apparent homogeneity as judged by polyacrylamide-gel electrophoresis, exhibited an absorbance ratio (A412/A280) of 0.783. Its Mr (44000 +/- 1000) and spectral properties were similar to those of the pig intestinal enzyme. The velocity constant for the reaction between rat intestinal peroxidase and hydrogen peroxide was found to be 1.8 x 10(7) M-1 . s-1. Benzhydroxamic acid inhibited the peroxidative oxidation of guaiacol by intestinal peroxidase from both species but the concentration required to cause half-inhibition of the enzyme from the rat was higher by one order of magnitude than for the pig enzyme. The amino acid composition of highly-purified pig intestinal peroxidase showed a relative abundance of basic amino acids (lysine and arginine) and was similar to that of lactoperoxidase, but not that of myeloperoxidase. The initial ten amino acid residues of this enzyme (the first reported partial sequence for a mammalian peroxidase) were also determined.

Amino Acid Sequence↗
PubMed1983

Immunological relationship between peroxidases in eosinophils, uterus and other tissues of the rat.

A rabbit antibody against purified pig intestinal peroxidase was shown by means of Western blotting and immunodetection to bind to peroxidases in various rat tissues, including eosinophils, uterus, uterine fluid and mammary tumours, and also to bind to bovine lactoperoxidase. The peroxidase in all rat tissues had an Mr of 53 000, except for uterine fluid, in which the cross-reacting band had an Mr of 80 000. The results indicate that while some of the peroxidase present in uterine tissue could be derived from eosinophils, the enzyme secreted into the lumen of the uterus is likely to have a different origin. They also suggest that mammary tumour peroxidase could originate from infiltration by eosinophils.

Animals↗
PubMed1990

The cellular location and specificity of bacterial cytochrome c peroxidases.

The locations of cytochrome c peroxidase and catalase activities in the two Gram-negative bacteria Pseudomonas stutzeri (N.C.I.B. 9721) and Paracoccus denitrificans (N.C.I.B. 8944) were investigated by the production of spheroplasts. In both species the cytochrome c peroxidase was predominantly periplasmic: 92% of total activity in Ps. stutzeri and 98% of nonmembrane-bound activity in Pa. denitrificans were found in this cellular compartment. In contrast, the catalase was mostly in the cytoplasmic fraction. Purification of the Pa. denitrificans cytochrome c peroxidase showed it to be the haem c-containing polypeptide of Mr 42,000 that has already been described by Bosma, Braster, Stouthamer & Van Versefeld [(1987) Eur. J. Biochem. 165, 665-670] but was not identified by them as a peroxidase. The visible-absorption spectra of the enzyme closely resemble those of cytochrome c peroxidase from Pseudomonas aeruginosa but the donor specificity is different, with the Pa. denitrificans enzyme preferring the basic mitochondrial cytochromes c to the acidic cytochromes c-551 and reacting well with the Pa. denitrificans cytochrome c-550.

Bacterial Proteins↗
PubMed1994

Synthesis of dehydrogenation polymers of ferulic acid with high specificity by a purified cell-wall peroxidase from French bean (Phaseolus vulgaris L.).

A cationic (pI 8.3) wall-bound peroxidase has been purified to homogeneity from suspension-cultured cells of French bean (Phaseolus vulgaris L.). The enzyme was a glycoprotein and its M(r) was 46,000 as determined by SDS/Page and h.p.l.c. gel filtration. It was localized biochemically to microsomes and the cell wall, and the latter subcellular distribution was confirmed by immunogold techniques. The native enzyme showed absorption maxima at 403, 500 and 640 nm, with an RZ (A405/A280) of 3.3. The peroxidase oxidized guaïacol and natural phenolic acids. By desorption-chemical-ionization mass spectrometry the enzyme was found to oxidize the model compound, ferulic acid, into dehydrodiferulic acid. Kinetics studies indicated an apparent Km of 113.3 +/- 22.9 microM and a Vmax of 144 mumol.min-1.nmol-1 of protein at an H2O2 concentration of 100 microM. In comparison with a second French-bean peroxidase (FBP) and horseradish peroxidase, as a model, it acted with a 6-10-fold higher specificity in this capacity. It is a member of the peroxidase superfamily of bacterial, fungal and plant haem proteins by virtue of its highly conserved amino acid sequence within the proximal and distal haem-binding sites. This is good evidence that this particular FBP may function in constructing covalent cross-linkages in the wall during development and response to pathogens.

Amino Acid Sequence↗