Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ascorbate peroxidase is a widespread plant enzyme that catalyzes the removal of potentially harmful H2O2. This enzyme is particularly important in legume root nodules due to their high potential for generating activated forms of oxygen. A cDNA clone of soybean nodule ascorbate peroxidase was used to construct an expression system in Escherichia coli. The recombinant protein had an N-terminal tag of six consecutive histidine residues to allow for purification by Ni(2+)-agarose affinity chromatography. Large amounts of recombinant peroxidase (about 27% of total soluble protein) were produced but most of the peroxidase was present in the apo-form (without heme). Addition of delta-aminolevulinic acid to the growth media resulted in an increase in production of holoprotein. Apoprotein was easily converted to the holo-form by in vitro reconstitution with hemin. The reconstituted protein was catalytically, spectrally, and immunologically indistinguishable from native ascorbate peroxidase.
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PMID:Heterologous expression and characterization of soybean cytosolic ascorbate peroxidase. 863 16

Ascorbate peroxidase (EC 1.11.1.11) has been purified to electrophoretic homogeneity from Euglena gracilis Z. The enzyme showed a molecular mass of 58 kDa on SDS-PAGE and gel filtration, indicating that Euglena ascorbate peroxidase exists as a monomeric form. The substrate specificity for an electron donor and the stability of the purified enzyme were similar to those of cytosolic isozymes from higher plants. One of the characteristic properties was that Euglena ascorbate peroxidase reduces organic hydroperoxides as well as hydrogen peroxide. The N-terminal amino-acid sequence showed no significant similarity to any other ascorbate peroxidase from higher plants. However, the sequence of the peptides from the purified enzyme exhibited a high degree of homology to sequences of cytosolic and chloroplastic ascorbate peroxidases. Monoclonal antibodies against the purified Euglena ascorbate peroxidase were prepared. Two monoclonal antibodies (EAP1 and EAP2) showed high homology to cytosolic ascorbate peroxidases of higher plants, as judged by Western blot analysis. The EAP1 was also specific for chloroplastic ascorbate peroxidase from spinach. These findings indicate that Euglena ascorbate peroxidase exists in highly homologous regions with the ascorbate peroxidases of higher plants.
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PMID:Molecular characterization of Euglena ascorbate peroxidase using monoclonal antibody. 864 9

Ole e 1, the major allergen from olive pollen, is a glycoprotein containing a single Asn-linked glycan moiety. Rabbit antiserum against this protein has been obtained; and its immunologic cross-reactivities in Western blotting with ascorbate oxidase, horseradish peroxidase, bromelain, ovalbumin, and honeybee venom phospholipase A2 have been studied. Ascorbate oxidase, peroxidase, and bromelain are recognized by the Ole e 1 antiserum. When these three proteins are deglycosylated by periodate treatment, such an immunologic reaction does not occur. The relative affinities of these proteins have been analyzed by direct and inhibition ELISA experiments. A commercially available antibody against horseradish peroxidase has also been considered in these studies. This antibody reacts with Ole e 1 but not with the periodate-deglycosylated allergen. Horseradish peroxidase, bromelain, and ascorbate oxidase are recognized by the IgE of sera from patients who are hypersensitive to olive tree pollen. This binding is also abolished by periodate treatment. The results are interpreted in terms of the presence of an epitope in the carbohydrate moiety of Ole e 1, which would contain a xylose involved in recognition by both IgE and IgG antibodies.
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PMID:Cross-reactivity between the major allergen from olive pollen and unrelated glycoproteins: evidence of an epitope in the glycan moiety of the allergen. 864 22

The accumulation of 2.2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical catalyzed by peroxidase can be inhibited by the presence of L-ascorbic acid in the reaction medium, this inhibition delaying the accumulation of the ABTS radical and giving rise to a lag time. A kinetic approach to explain this lag time is presented, which also makes it possible to determine the amount of L-ascorbic acid in the reaction medium. The stoichiometry of the system was determined as 1 mol of L-ascorbic reducing 2 mol of ABTS radicals. L-Ascorbic acid is not the only compound to have this ability, since other antioxidant compounds also react with the ABTS radical. We studied the ABTS/H2O2/horseradish peroxidase system in the presence of L-ascorbic acid and other antioxidant compounds. The influence of such factors as pH, enzyme concentration, and L-ascorbic acid concentration was studied. A good correlation between the lag time and the L-ascorbic acid present in the medium was observed, and under optimal conditions, the method could determine as little as 0.65 nmol of L-ascorbic acid. Based on our findings, we propose a method to measure the total antioxidant activity of different compounds related to L-ascorbic acid and apply this method to determining the total antioxidant activity present in fruit juices.
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PMID:Inhibition by L-ascorbic acid and other antioxidants of the 2.2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) oxidation catalyzed by peroxidase: a new approach for determining total antioxidant status of foods. 866 May 2

Oxidative damage (lipid peroxidation, LPO) induced in a completely defined system containing glutathione (GSH), purified gamma-glutamyl transpeptidase (GGT), and EDTA- and ADP-chelated ferric iron was enhanced by catalytic amounts of cupric ions and by ceruloplasmin (CP). The enhancement depended on GSH concentration, GGT activity, the presence of iron, and the chelation of copper by o-phenanthroline. High concentrations of CP inhibited LPO. Cu- and CP-enhanced, GSH-GGT-driven LPO was inhibited by the chain-breaking radical scavengers butylated hydroxyanisol, alpha-tocopherol, and Trolox C (a synthetic analog of alpha-tocopherol) but not by the hydroxyl scavenger mannitol. Ascorbic acid increased LPO in the presence of Cu or CP. Cu-enhanced LPO was partially sensitive to superoxide dismutase but not to catalase or horseradish peroxidase. The results indicate that Cu and CP enhance thiol-driven LPO and promote thiol-dependent mutagenesis by a very similar, if not the same, mechanism and are in agreement with the idea that this enhancement is due to redox reactions of chelated Cu and Fe, rather than to the reactivity of Cu in the Fenton reaction.
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PMID:Promotion of glutathione-gamma-glutamyl transpeptidase-dependent lipid peroxidation by copper and ceruloplasmin: the requirement for iron and the effects of antioxidants and antioxidant enzymes. 902 Mar 10

Phenolphthalein, a widely used laxative, is the active ingredient in more than a dozen commercial nonprescription formulations. Fast-flow EPR studies of the reaction of phenolphthalein with horseradish peroxidase (HRP) and hydrogen peroxide permit the direct detection of two free radicals. One has EPR parameters characteristic of phenoxyl radicals. The other has a broad unresolved spectrum, possibly arising from free radical polymeric products of the initial phenoxyl radical. EPR spin-trapping studies of incubations of phenolphthalein with lactoperoxidase, reduced glutathione (GSH), and hydrogen peroxide with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) demonstrate stimulated production of DMPO/.SG compared with an identical incubation lacking phenolphthalein. In the absence of DMPO, measurements with a Clark-type oxygen electrode show that molecular oxygen is consumed by a sequence of reactions initiated by the glutathione thiyl radical. Enhanced production of DMPO superoxide radical adduct is also found in a system of phenolphthalein, NADH, and lactoperoxidase. In this system the phenolphthalein phenoxyl radical abstracts hydrogen from NADH to generate NAD., which is not spin trapped by DMPO, but reacts with molecular oxygen to produce the superoxide radical detected by EPR. In the absence of DMPO, the oxygen consumption is measured using the Clark-type electrode. Production of ascorbate radical anion is also enhanced in a system of phenolphthalein, ascorbic acid, hydrogen peroxide, and lactoperoxidase. Ascorbate inhibits oxygen consumption when phenolphthalein is metabolized in the presence of either glutathione or NADH by reducing radical intermediates to their parent molecules and forming the relatively stable ascorbate anion radical. The detection of enhanced free radical production in these three systems, a consequence of futile metabolism (or redox cycling), suggests that phenolphthalein may be a significant source of oxidative stress in physiological systems. Parallel EPR and oxygen consumption studies with phenolphthalein glucuronide give analogous results, but with lesser enhancement of free radical production.
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PMID:In vitro free radical metabolism of phenolphthalein by peroxidases. 910 47

Salt damage to plants has been attributed to a combination of several factors including mainly osmotic stress and the accumulation of toxic ions. Recent findings in our laboratory showed that phospholipid hydroperoxide glutathione peroxidase (PHGPX), an enzyme active in the cellular antioxidant system, was induced by salt in citrus cells and mainly in roots of plants. Following this observation we studied the two most important enzymes active in elimination of reactive oxygen species, namely, superoxide dismutase (SOD) and ascorbate peroxidase (APX), to determine whether a general oxidative stress is induced by salt. While Cu/Zn-SOD activity and cytosolic APX protein level were similarly induced by salt and methyl viologen, the response of PHGPX and other APX isozymes was either specific to salt or methyl viologen, respectively. Unlike PHGPX, cytosolic APX and Cu/Zn-SOD were not induced by exogenously added abscisic acid. Salt induced a significant increase in SOD activity which was not matched by the subsequent enzyme APX. We suggest that the excess of H2O2 interacts with lipids to form hydroperoxides which in turn induce and are removed by PHGPX. Ascorbate peroxidase seems to be a key enzyme in determining salt tolerance in citrus as its constitutive activity in salt-sensitive callus is far below the activity observed in salt-tolerant callus, while the activities of other enzymes involved in the defence against oxidative stress, namely SOD, glutathione reductase and PHGPX, are essentially similar.
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PMID:Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in citrus. 942 31

Ascorbate peroxidase (APX) is a hydrogen peroxide-scavenging peroxidase which uses ascorbate (AsA) as the specific electron donor. APX has not been isolated in mammals. Ocular tissue contains AsA at high concentrations, and we detected APX activity in bovine retinal pigment epithelium (RPE) and choroid. We purified APX from bovine RPE and choroid by four chromatographic steps. The purified APX was a monomeric hemoprotein with a molecular mass of 43 kDa. The amino acid sequence of the amino-terminal region of the purified APX showed a high degree of homology to that of plants. The primary product of the APX reaction was identified as the monodehydroascorbate radical. The APX showed high specificity for AsA as an electron donor. This is the first isolation and characterization of APX from mammals, and its role in the protection against active species of oxygen in ocular tissue is discussed.
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PMID:Purification and molecular properties of ascorbate peroxidase from bovine eye. 944 80

Ascorbate peroxidase (AP) is a key enzyme that scavenges potentially harmful H2O2 and thus prevents oxidative damage in plants, especially in N2-fixing legume root nodules. The present study demonstrates that the nodule endodermis of alfalfa (Medicago sativa) root nodules contains elevated levels of AP protein, as well as the corresponding mRNA transcript and substrate (ascorbate). Enhanced AP protein levels were also found in cells immediately peripheral to the infected region of soybean (Glycine max), pea (Pisum sativum), clover (Trifolium pratense), and common bean (Phaseolus vulgaris) nodules. Regeneration of ascorbate was achieved by (homo)glutathione and associated enzymes of the ascorbate-glutathione pathway, which were present at high levels. The presence of high levels of antioxidants suggests that respiratory consumption of O2 in the endodermis or nodule parenchyma may be an essential component of the O2-diffusion barrier that regulates the entry of O2 into the central region of nodules and ensures optimal functioning of nitrogenase.
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PMID:Antioxidant defenses in the peripheral cell layers of legume root nodules. 944 34

Chlorins are cyclic tetrapyrrole derivatives of great interest for use in photodynamic therapy. We have found that horseradish peroxidase (EC 1.11.1.7) (HRP) can convert deuteroporphyrin IX (Deutero) into chlorins. Some characteristics of this enzymatic transformation were investigated. The formation of chlorins was determined spectrophotometrically by monitoring the change in absorbance in the Q-band region (638 nm). The reaction occurred without addition of H2O2 and had a pH optimum of 7.5. The presence of thiol-containing reductants, with a great preference for reduced glutathione, was required and could not be substituted by adding H2O2. Ascorbic acid acted as a potent inhibitor of the reaction, while other organic acids (citric and benzoic) had little to no inhibitory effect. The requirement for O2 was suggested by the inhibitory effect of sodium hydrosulfite and was confirmed by carrying the assay in nitrogen-saturated solutions. Though the reaction occurred without adding H2O2, low amounts of H2O2 (3-30 microM) were stimulatory to the assay. However, concentrations of 300 microM H2O2 or higher were inhibitory. Similarly, light was not required, but was stimulatory at low levels and inhibitory at high levels. Catalase and deferoxamine were inhibitory, but superoxide dismutase and mannitol had no effects. Kinetic analysis and respiratory studies suggest that HRP may initially react with reduced glutathione in a reaction that does not consume much oxygen. The ensuing steps, probably involving an oxygen free radical and porphyrin radical intermediates, consume a large amount of O2 to oxidize Deutero into chlorin.
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PMID:Horseradish peroxidase-dependent oxidation of deuteroporphyrin IX into chlorins. 950 Aug 44


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