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At least 127 records · Page 7Linked to original sources
PubMed2000

Thioredoxin-dependent hydroperoxide peroxidase activity of bacterioferritin comigratory protein (BCP) as a new member of the thiol-specific antioxidant protein (TSA)/Alkyl hydroperoxide peroxidase C (AhpC) family.

Escherichia coli bacterioferritin comigratory protein (BCP), a putative bacterial member of the TSA/AhpC family, was characterized as a thiol peroxidase. BCP showed a thioredoxin-dependent thiol peroxidase activity. BCP preferentially reduced linoleic acid hydroperoxide rather than H(2)O(2) and t-butyl hydroperoxide with the use of thioredoxin as an in vivo immediate electron donor. The value of V(max)/K(m) of BCP for linoleic acid hydroperoxide was calculated to be 5-fold higher than that for H(2)O(2), implying that BCP has a selective capability to reduce linoleic acid hydroperoxide. Replacement of Cys-45 with serine resulted in the complete loss of thiol peroxidase activity, suggesting that BCP is a new bacterial member of TSA/AhpC family having a conserved cysteine as the primary site of catalysis. BCP exists as a monomer, and its functional Cys-45 appeared to exist as cysteine sulfenic acid. The expression level of BCP gradually elevated during exponential growth until mid-log phase growth, beyond which the expression level was decreased. BCP was induced 3-fold by the oxidative stress given by changing the growth conditions from the anaerobic to aerobic culture. Bcp null mutant grew more slowly than its wild type in aerobic culture and showed the hypersensitivity toward various oxidants such as H(2)O(2), t-butyl hydroperoxide, and linoleic acid hydroperoxide. The peroxide hypersensitivity of the null mutant could be complemented by the expression of bcp gene. Taken together, these data suggest that BCP is a new member of thioredoxin-dependent TSA/AhpC family, acting as a general hydroperoxide peroxidase.

Amino Acid Sequence↗
PubMed1996

Selenium-dependent peroxidases suppress 5-lipoxygenase activity in B-lymphocytes and immature myeloid cells. The presence of peroxidase-insensitive 5-lipoxygenase activity in differentiated myeloid cells.

Differentiation of HL-60 cells by dimethylsulfoxide induces 5-lipoxygenase protein expression, but only low cellular 5-lipoxygenase activity. Similarly, B-lymphocytes express 5-lipoxygenase protein and show activity in cell homogenates but not in intact cells. Here, we demonstrate that suppression of cellular 5-lipoxygenase activity in these cell lines is serum dependent and that the serum effect can be mimicked by selenium. Selenium-dependent inhibition of 5-lipoxygenase activity was also observed in the corresponding cell homogenates or 100,000 x g supernatants when dithiothreitol or glutathione (GSH) was added. The properties of the endogenous selenium-dependent inhibitor, i.e., molecular mass, utilization of GSH and dithiothreitol as substrates, sensitivity to iodacetate, inhibition of 5-lipoxygenase activity in the presence of the GPx-1 inhibitor mercaptosuccinate, suggest that a selenoenzyme with properties of the phospholipid hydroperoxide glutathione peroxidase (GPx-4) is responsible for the 5-lipoxygenase inhibition in BL41-E95-A and immature HL-60 cells. Differentiation of HL-60 cells in the presence of 1,25-dihydroxyvitamin D3 and transforming growth factor-beta (TGF beta) upregulated cellular 5-lipoxygenase activity regardless of whether the cell were grown with or without serum or selenium. Also, 5-lipoxygenase activity in homogenates or 100,000 x g supernatants of 1,25-dihydroxyvitamin D3/TGF beta differentiated HL-60 cells and of human granulocytes was not inhibited by dithiothreitol or GSH. Thus, after 1,25-dihydroxyvitamin D3/TGF beta differentiation, HL-60 cells resemble normal granulocytes with respect to the high 5-lipoxygenase activity in intact cells and to the dithiothreitol effects in broken cell preparations. Combination experiments with 100000 x g supernatants of BL41-E95-A cells and neutrophils revealed that the high 5-lipoxygenase activity of granulocytes is due to stability of the 5-lipoxygenase catalytic activity against selenium-dependent peroxidases, but not to low peroxidase activity. Our data suggest that the capability of mature myeloid cells to release large amounts of leukotrienes after stimulation is due to a peroxidase-insensitive 5-lipoxygenase catalytic activity.

Arachidonate 5-Lipoxygenase↗
PubMed2000

The cloning of a new peroxidase found in lignocellulose cultures of Pleurotus eryngii and sequence comparison with other fungal peroxidases.

We report cloning and sequencing of gene ps1 encoding a versatile peroxidase combining catalytic properties of lignin peroxidase (LiP) and manganese peroxidase (MnP) isolated from lignocellulose cultures of the white-rot fungus Pleurotus eryngii. The gene contains 15 putative introns, and the deduced amino acid sequence consists of a 339-residue mature protein with a 31-residue signal peptide. Several putative response elements were identified in the promoter region. Amino acid residues involved in oxidation of Mn(2+) and aromatic substrates by direct electron transfer to heme and long-range electron transfer from superficial residues as predicted by analogy with Phanerochaete chrysosporium MnP and LiP, respectively. A dendrogram is presented illustrating sequence relationships between 29 fungal peroxidases.

Amino Acid Sequence↗
PubMed1999

[The role of the extent of hydration of reversed micelles of surfactant s in the regulation of the peroxidase activity of ferritin and immunocomplexes of cortisol-peroxidase conjugates].

The effect of the degree of hydration (W0) of reversed micelles of Aerosol OT (AOT) and its mixture with Triton X-45 in heptane on the peroxidase activity of horse spleen ferritin in the oxidation of various substrates by hydrogen peroxide and organic hydroperoxides and on the activity of solubilized or immobilized immunocomplexes of horseradish peroxidase-cortisol conjugates (HP-COR) was studied. The peroxidase activity versus W0 plot has maxima at W0 8-14 and 19-22, which cannot be attributed to dissociation of immunocomplexes into its components or of ferritin into its subunits. The possibility of the stabilization of the conformers of oligomeric proteins by reversed micelles and the effect of the self-association of micelles on the peroxidase activity of the HP-COR immunocomplexes and ferritin were discussed. A procedure for the isolation of the iron-containing cluster from the ferritin molecule without reduction of the Fe3+ ions was suggested.

Animals↗
PubMed1998

Evidence for indole-3-acetic acid binding site in plant peroxidases. Structural similarity between peroxidases and auxin-binding proteins.

Application of computer methods allowed us to demonstrate that plant peroxidases and auxin-binding proteins contain structurally similar fragments. The mapping of the fragments was done using a model structure of horseradish peroxidase. Five of six structurally similar fragments belong to the distal domain and form a subdomain in plant peroxidases that includes the distal heme-coordinating sequence, LHFHDC (amino acid residues 39-44 in horseradish peroxidase). The existence of a substrate-binding site for indole-3-acetic acid in the distal subdomain comprising helices A (whole), B (middle), C (beginning), and D (whole) and the loop between helices D and D' is discussed.

Amino Acid Sequence↗
PubMed2006

QM/MM modeling of compound I active species in cytochrome P450, cytochrome C peroxidase, and ascorbate peroxidase.

QM/MM calculations provide a means for predicting the electronic structure of the metal center in metalloproteins. Two heme peroxidases, Cytochrome c Peroxidase (CcP) and Ascorbate Peroxidase (APX), have a structurally very similar active site, yet have active intermediates with very different electronic structures. We review our recent QM/MM calculations on these systems, and present new computational data. Our results are in good agreement with experiment, and suggest that the difference in electronic structure is due to a large number of small differences in structure from one protein to another. We also discuss recent QM/MM calculations on the active species of cytochrome P450, in which a similar sensitivity of the electronic structure to the environment is found. However, this does not appear to explain different catalytic profiles of the different drug-metabolizing isoforms of this class of enzyme.

Ascorbate Peroxidases↗
PubMed1988

Oxidation of catechol by horseradish peroxidase and human leukocyte peroxidase: reactions of o-benzoquinone and o-benzosemiquinone.

The metabolism of secondary phenolic metabolites of benzene, such as catechol, by peroxidases represents one possible mechanism underlying benzene-induced myelotoxicity. The oxidation of catechol by horseradish peroxidase and peroxidases present in human leukocytes was therefore examined. Peroxidatic oxidation resulted in o-benzoquinone production, which was characterized as its bromothiophenol adduct. o-Benzoquinone-glutathione conjugates were formed during peroxidatic oxidation of catechol in the presence of glutathione. Both mono- and diglutathione conjugates were detected. As much as 80% of catechol removed during peroxidatic oxidation could be recovered as glutathione conjugates of o-benzoquinone. Glutathione had no inhibitory effect on the removal of catechol during peroxidatic oxidation. In the presence of divalent cations (Mg2+, Zn2+), however, which slow the rate of o-semiquinone disproportionation, glutathione was found to inhibit catechol removal. This suggests that in the absence of stabilizing metal, reduction of the o-benzosemiquinone radical by glutathione cannot compete with other rapid reactions of the radical such as disproportionation. No interaction of the o-benzosemiquinone radical with oxygen could be detected even in the presence of stabilizing metals or superoxide dismutase which inhibits the reverse reaction of the SQ + O2 in equilibrium Q + O.2 equilibrium. Thus, under physiological conditions, glutathione and oxygen would not be expected to reduce or oxidize respectively the o-benzosemiquinone radical. These data show that the generation of thiol conjugates of o-benzoquinone can be used as probes of peroxidatic oxidation of catechol.

Benzoquinones↗
PubMed1984

Genetically determined conidial longevity is positively correlated with superoxide dismutase, catalase, glutathione peroxidase, cytochrome c peroxidase, and ascorbate free radical reductase activities in Neurospora crassa.

Aging of post-mitotic cells, the conidia, of Neurospora crassa is defined as the time-dependent loss of viability under a constant laboratory environment which probably resembles the organism's tropical habitat; namely, at 30 degrees C, 85-100% relative humidity under white light. Median lifespan is defined as the age at which survival of a conidial population has declined to 50% of that of a fully viable population at birth. A collection of short (age-) and long-lived (age+) mutants were previously selected from the wild-type whose median lifespan is 22 days. Thus, five groups of strains with distinct lifespans of 7, 22, 36, 50 and 60 days were defined. The purposes of the present investigation were to determine if the activities of anti-oxygenic enzymes are correlated with lifespan and to elucidate the function of the cellular longevity determinant genes. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) were highly-correlated with lifespan; whereas glutathione reductase and non-specific peroxidase activities were not correlated. The short-lived mutants were also deficient in cytochrome c peroxidase (CPX) and ascorbate free radical reductase (AFR), but not deficient in dehydroascorbate reductase. (These latter three enzymes were not examined in age+ mutants.) By isoelectric focusing analysis, the deficiencies of SOD, CAT, and GPX activities of age- mutants were defined in terms of specific isozymes. The mutants were specifically deficient in a cyanide-resistant mitochondrial isozyme of SOD. Sixteen age- genes, called the age-1 complex, were previously mapped on one arm of the seven chromosomes. On the basis of mapping and complementation data, it was inferred that the genes are spatially and functionally redundant. The hypothesis of functional redundancy is also supported by the enzyme data. Of seven mutants examined, representing seven of the age- genes, all were deficient in SOD, CAT and CPX, and six were deficient in AFR. Of four mutants examined, representing four of the genes, all were deficient in GPX. The results indicate a molecular basis for the previously observed photosensitivity of the mutants.(ABSTRACT TRUNCATED AT 400 WORDS)

Catalase↗
PubMed1986

The formation of ES of cytochrome-c peroxidase: a comparison with lactoperoxidase and horseradish peroxidase.

The activation energy for the formation of the first red compound, ES, for cytochrome-c peroxidase (ferrocytochrome-c: hydrogen-peroxide oxidoreductase, EC 1.11.1.5) by i-propyl hydroperoxide and the rate constants for the formation of ES with various hydroperoxides have been determined. Multivariate data analysis by the partial least-squares model in latent variables has been used to compare the rate constants with the corresponding rate constants for the formation of compound I from lactoperoxidase and two isoenzymes of horseradish peroxidase. The results show that the rate of formation of ES from cytochrome-c peroxidase is highly correlated with the pKa of the hydroperoxides. The activation energy for the formation of ES with i-propyl hydroperoxide is close to the corresponding value for hydrogen peroxide.

Cytochrome-c Peroxidase↗
PubMed1994

Molecular dynamics studies on peroxidases: a structural model for horseradish peroxidase and a substrate adduct.

Molecular dynamics (MD) calculations are performed on cytochrome c peroxidase (CcP) and on horseradish peroxidase, isoenzyme C (HRP), and its substrate adduct with p-cresol. For CcP, a refinement in solution of the X-ray structure is obtained which indicates that in solution the protein structure is very similar to that in the crystal. For HRP, the X-ray structure is not available. We have generated a model of this protein based on the recently reported structure of the similar lignin peroxidase (LiP) protein. This model involves the entire system as all the amino acid residues match the sequence. This HRP model was refined through energy minimization and MD calculations. A refined structural model for HRP, for the first time involving the entire protein, is therefore now available. The tertiary structure of HRP is close to that of LiP, and also the active site in the two proteins has significantly similar structures. The well-ordered water molecules and the extensive H-bond network present in the X-ray structure of CcP is maintained in the dynamics without any constraints, indicating that the active site residues produce a field strong enough to make all these interactions quite stable. Interestingly, also in HRP a network of ordered water molecules and H-bonds is present, again without constraints. This is consistent with the similarities of the active sites in the two proteins. Finally, we have calculated the MD structure of the adduct of HRP and a substrate molecule, p-cresol. This structural model is compared with the NMR data, which are in fairly good agreement. The binding site and the protein-substrate interactions are discussed.

Binding Sites↗
PubMed1989

Thyroid microsomal/thyroid peroxidase autoantibodies show discrete patterns of cross-reactivity to myeloperoxidase, lactoperoxidase and horseradish peroxidase.

The recent cloning of the thyroid peroxidase (TPO) has shown that it is identical to the thyroid microsomal antigen (TMA), a potent antigen involved in autoimmune thyroid disease (ATD), which shares significant sequence homology with myeloperoxidase. The present study shows that autoantibodies (aAb) to the TMA/TPO antigen cross-react with human leucocyte myeloperoxidase, bovine lactoperoxidase and horseradish peroxidase. Cross-reactivity to myeloperoxidase was only apparent by ELISA using reduced and alkylated antigen preparations or by immunoblotting following denaturation with SDS. Sequential absorption of sera on SDS-denatured thyroid microsomes immobilized on Sepharose-4B followed by absorption on native microsomes removed all aAb specificities to TMA/TPO and the three peroxidase preparations, giving compelling evidence on the genuine cross-reactive nature of these aAbs. Sera from different patients contain different qualitative and quantitative specificities of aAb to the TMA/TPO antigen, confirming the polyclonal nature of this autoimmune response.

Absorption↗
PubMed1986

Peroxidase activity at consecutive nodes of Ranvier in the nerve to the medial gastrocnemius muscle after intramuscular administration of horseradish peroxidase.

The distribution of axoplasmic organelles at consecutive nodes of Ranvier was investigated light- and electronmicroscopically in horseradish peroxidase-transporting muscle nerve fibres of the adult cat. Three main and apparently temporally interrelated distribution patterns were noted. These patterns were referred to as A, B and C. The axoplasm of type-A and type-B nodes was highly segregated with regard to the proximodistal distribution of certain organelles. At type-A nodes horseradish peroxidase-positive membrane limited bodies and horseradish peroxidase-negative vesiculotubular membrane profiles were accumulated just distal and just proximal to the nodal mid-level, respectively. At B nodes a disc-like accumulation of enzyme activity, that was situated a few micron proximal to the mid-level, added to the type-A pattern. The type-C node showed a barely segregated axoplasm in which horseradish peroxidase-positive bodies were distributed randomly. We suggest, on the basis of the mutual order of the nodal types in a sequence of consecutive nodes and their appearance relative to the time after the administration of the HRP, that the different axoplasmic patterns reflect the operation of an ordered process that delays part of the retrogradely transported HRP for 2-3 days. The large number of lysosome-like HRP positive bodies that appeared at the nodes during this process indicates that the nodal axoplasm not only delays but also might take part in the degradation of the foreign protein.

Acid Phosphatase↗
PubMed1991

Combined use of in situ hybridization and unlabeled antibody peroxidase anti-peroxidase methods: simultaneous detection of type I procollagen mRNAs and factor VIII-related antigen epitopes in keloid tissue.

In this study, we developed methodology that allows the combined use of in situ hybridization and peroxidase anti-peroxidase techniques on the same tissue section. A human pro alpha 1(I) collagen cDNA and antibodies to factor VIII-related antigen were used on keloid tissue sections as a model for a fibrotic reaction. The basic protocols of the techniques were modified to obtain optimal results. The feasibility of this new method was demonstrated by elucidation of type I procollagen gene expression in the cells of blood vessel wall and the adjacent fibroblasts. In the case of capillaries, pro alpha 1(I) collagen mRNAs were detected within endothelial cells identified by the presence of factor VIII-related antigen. Pro alpha 1(I) collagen mRNAs were also found in close proximity of medium-size blood vessels, but in this context clearly outside the vessel wall. These results may contribute to the understanding of pathogenetic aspects of keloids and other fibrotic conditions. Thus, the combination of in situ hybridization and peroxidase anti-peroxidase techniques provides a useful tool to examine gene expression simultaneously both at mRNA and protein levels in fibrotic tissues. This methodology is also applicable to a variety of other biologic and pathologic situations.

DNA↗
PubMedDate not supplied

Effect of polymers on enhanced chemiluminescent assays for peroxidase and peroxidase labels.

Hydroxypropyl methylcellulose, hydroxyethyl cellulose, and hydroxybutyl methylcellulose stabilized light emission in a boronic acid-enhanced chemiluminescent assay for horseradish peroxidase. The stabilization of light emission was concentration-dependent and more effective with substituted boronic acid enhancers (e.g. 4-iodophenylboronic acid) than with substituted phenol enhancers (e.g. 4-iodophenol). Hydroxybutyl methylcellulose improved the linearity of the dose-response curve in a peroxidase-based antioxidant assay and stabilized light emission post-consumption of the antioxidant (Trolox). This polymer had no effect on the signal from a peroxidase label immobilized on a membrane (dot blot) or on the inside surface of a microwell in an enzyme immunoassay for thyrotropin.

Antioxidants↗
PubMed1998

Class I heme peroxidases: characterization of soybean ascorbate peroxidase.

An efficient expression system [D. A. Dalton et al. Arch. Biochem. Biophys. 328, 1-8, 1996) for soybean nodule ascorbate peroxidase (APX) has, for the first time, been used to generate enzyme in large enough quantities for detailed biophysical analysis. The recombinant APX has been characterized by electronic absorption, EPR, NMR and circular dichroism spectroscopies, and by electrochemistry. Electronic, EPR, and NMR spectra are consistent with a high-spin ferric resting state for the enzyme at 298 K. Low-temperature EPR (7 K) and electronic absorption (77 K) experiments indicate formation of a low-spin heme derivative at these temperatures. The midpoint reduction potential for the Fe(III)/Fe(II) redox couple, determined by spectroelectrochemistry, is -159 +/- 2 mV vs SHE (pH 7.0, 25.0 degrees C, mu = 0.10 M). Circular dichroism spectra of pea and soybean APXs are very similar, indicating common structural features for the two enzymes. The melting temperature of soybean APX, as monitored by circular dichroism spectroscopy, is 49 degrees C. These results represent the first detailed spectroscopic and electrochemical analysis of soybean ascorbate peroxidase and are discussed in the broader context of other class I peroxidases.

Amino Acid Sequence↗
PubMed1991

Peroxidase-catalyzed bromination of tyrosine, thyroglobulin, and bovine serum albumin: comparison of thyroid peroxidase and lactoperoxidase.

A recent paper (Buchberger, W., 1988, J. Chromatogr. 432, 57) on lactoperoxidase-catalyzed bromination of tyrosine and thyroglobulin stated, without evidence, that thyroid peroxidase (TPO) is able to use bromide as a substrate. This was in disagreement with unpublished experiments previously performed in this laboratory, and we undertook, therefore, to examine this subject further. Highly purified porcine TPO was compared with lactoperoxidase (LPO) and chloroperoxidase (CPO) for ability to catalyze bromination of tyrosine, thyroglobulin, and bovine serum albumin (BSA). The incubation mixture contained 50-100 nM peroxidase, 10-500 microM 82Br-, tyrosine (150 microM), thyroglobulin (0.3 or 1 microM), or BSA (7.5 microM), and a source of H2O2. The latter was either generated by glucose (1 mg/ml)-glucose oxidase (0.5 or 1 micrograms/ml), or added initially as a bolus (100 microM). With TPO, formation of organically bound 82Br was undetectable under all conditions in the pH range 5.4-7.0. Lactoperoxidase and CPO, on the other hand, displayed considerable brominating activity. Lactoperoxidase was much more active at pH 5.4 than at pH 7.0 and was more active with BSA as acceptor than with tyrosine or thyroglobulin. The distribution of 82Br among the various amino acids in LPO-brominated thyroglobulin and BSA was determined by HPLC. As expected, monobromotyrosine and dibromotyrosine together comprised the greatest part of the bound 82Br. However, a surprisingly high percentage (20-25%) was present as monobromohistidine. Evidence was also obtained for the presence of a small percentage of the bound 82Br as tetrabromothyronine. Peroxidase-catalyzed bromination probably depends on the oxidation of Br- to Br+ by the Compound I form of the enzyme. Since oxidation of Br- to Br+ requires a stronger oxidant than oxidation of I- to I+, our results suggest that Compound I of LPO and of CPO has a higher oxidation potential than Compound I of TPO. In vivo experiments with rats on a low iodine diet injected with 82Br- showed that even under conditions of high stimulation by thyrotropic hormone, there is negligible formation of organic bromine in the thyroid. Measurements of thyroid:serum concentration ratios for 82Br- in similar rats provided no evidence that Br- is a substrate for the iodide transport system of the thyroid.

Animals↗
PubMed1978

Rapid preparation of peroxidase: anti-peroxidase complexes for immunocytochemical use.

Soluble immune complexes of horseradish peroxidase and antibody to peroxidase (PAP) have been widely used in the 'unlabelled antibody' method for the immunocytochemical detection of cellular antigens. This paper describes a simple and rapid method for preparation of these complexes by column chromatography of a mixture of the enzyme and the IgG fraction of antiperoxidase antiserum on Sephacryl S-200. The material eluting in the void column consists of stable soluble PAP complexes, with a molar peroxidase: antiperoxidase ratio of 0.8 and a molecular weight of approximately 400,000. When tested immunocytochemically this material gives identical results to those obtained with conventionally prepared PAP.

Animals↗
PubMed1983

Deuterium exchangeable proton hyperfine resonances of low-spin cytochrome c peroxidase and the mechanism of peroxidase catalysis.

Deuterium exchangeable hyperfine proton NMR resonances of cytochrome c peroxidase (EC 1.11.1.5) are identified in H2O solutions of the enzyme. One of these is assigned to the proximal histidine's imidazole N-H. Its shift and pH dependence indicate that an imidazolate form, which has been postulated for peroxidases, is ruled out for cytochrome c peroxidase-cyanide. A qualitative comparison of relative heme-pocket dynamics is also possible. When the bulk water resonance is irradiated with a continuous, but off acquisition, decoupler frequency the N-H resonance shows no intensity loss, indicating that saturation transfer between the proximal histidine and solvent water is either minimal, or extremely slow.

Cytochrome-c Peroxidase↗