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)

Ascorbic acid, at physiological concentrations, can scavenge the myeloperoxidase-derived oxidant hypochlorous acid at rates sufficient to protect alpha 1-antiprotease against inactivation by this molecule. The rapid depletion of ascorbic acid at sites of inflammation, as in the inflamed rheumatoid joint, may therefore facilitate proteolytic damage.
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PMID:Biologically significant scavenging of the myeloperoxidase-derived oxidant hypochlorous acid by ascorbic acid. Implications for antioxidant protection in the inflamed rheumatoid joint. 303 Aug 5

The enzymes involved in antioxidative activity and the cellular content of the antioxidants glutathione and ascorbate in the cyanobacteria Nostoc muscorum 7119 and Synechococcus 6311 have been examined for their roles in hydroperoxide removal. High activities of ascorbate peroxidase and catalase were found in vegetative cells of both species and in the heterocysts of N. muscorum. The affinity of ascorbate peroxidase for H2O2 was 15- to 25-fold higher than that of catalase. Increased activity of ascorbate peroxidase was observed in N. muscorum when H2O2 production was enhanced by photorespiration. Catalase activity was decreased in dilute cultures whereas ascorbate peroxidase activity increased. Ascorbate peroxidase activity also increased when the CO2 concentration was reduced. Ascorbate peroxidase appears to be a key enzyme in a cascade of reactions regenerating antioxidants. Dehydroascorbate reductase was found to regenerate ascorbate, and glutathione reductase recycled glutathione. In vegetative cells glutathione was present in high amounts (2-4 mM) whereas the ascorbate content was almost 100-fold lower (20-100 microM). Glutathione peroxidase was not detected in either cyanobacterium. It is concluded from the high activity of ascorbate peroxidase activity and the levels of antioxidants found that this enzyme can effectively remove low concentrations of peroxides. Catalase may remove H2O2 produced under photooxidative conditions where the peroxide concentration is higher.
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PMID:Hydroperoxide metabolism in cyanobacteria. 308 78

Desirable characteristics of enzyme-antibody conjugates for use in enzyme immunoassay are labelling uniformity, permanent availability and stability. The use of monoclonal antibodies (McABS) for preparation of enzyme conjugates, in place of polyclonal antibodies, ensures labelling uniformity and permanent availability. The problem of stability still exists. Monoclonal antibody-horseradish peroxidase (McAB-HRPO) conjugates produced in our laboratory showed variable stability. After extensive testing of McAB-HRPO conjugates it became obvious that sodium borohydride, used as a reducing agent, did not result in the production of stable conjugates without enzyme pretreatment with fluorodinitrobenzene (FDNB). Ascorbic acid or ethanolamine used as the reducing agent, resulted in McAB-HRPO conjugates which were stable for periods of ten months or more when stored filter sterilized at 4 degrees C.
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PMID:Peroxidase-labelled monoclonal antibodies for use in enzyme immunoassay. 331 82

The nitrite ion is a direct causative agent for methemoglobinemia. Oxidation of hemoglobin to methemoglobin under aerobic conditions is induced by nitrite, catalyzed by methemoglobin in the presence of hydrogen peroxide, and inhibited by chemical reagents ranging from cysteine and ascorbic acid to sulfite. The stoichiometry of nitrate production is dependent on the initial [NO2-]/[HbO2] ratio, but reaches a limiting value of 1:1 [NO3-]: [Hb+] when [NO2-]/[HbO2] greater than 8. Ascorbic acid is an exceptionally effective inhibitor for the autocatalytic oxidation, but its use does not affect the stoichiometry of nitrate formation. Sulfite reduces nitrate production to a level that is half that observed in its absence. These chemical inhibitors act upon the rapid autocatalytic stage for hemoglobin oxidation, but they do not influence the slow direct oxidation of hemoglobin by nitrite. The autocatalytic stage for hemoglobin oxidation results from nitrogen dioxide formed from nitrite through the peroxidase activity of methemoglobin. Peroxide and methemoglobin are formed during the initiation stage by electron transfer from nitrite that is kinetically first order in oxyhemoglobin and in nitrite.
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PMID:Autocatalytic oxidation of hemoglobin induced by nitrite: activation and chemical inhibition. 383 41

Vitamin C (ascorbic acid), commonly taken as a dietary supplement and excreted in the urine, can interfere with peroxidase redox indicator systems such as those used in reagent-strip tests for urinary glucose and hemoglobin. We investigated whether the concentrations of ascorbic acid in urine after modest supplementary doses of vitamin C are high enough to interfere with such dipstick tests. After adding glucose or hemoglobin to urine collected from persons not taking vitamin C and from persons taking 350 to 1000 mg of vitamin C daily, we tested four reagent strips for interference and found that these commonly taken doses did frequently interfere with all test systems examined.
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PMID:Ascorbic acid interference in reagent-strip reactions for assay of urinary glucose and hemoglobin. 395 16

A continuous-flow assay for measuring oxalate in urine is described. Covalently attached oxalate oxidase (EC 1.2.3.4) is used to oxidize the oxalate anion to carbon dioxide and hydrogen peroxide. The formed hydrogen peroxide is measured colorimetrically (A580) with an established reaction using horseradish peroxidase (EC 1.11.17), 3-methyl-2-benzothiazolinone hydrazone (MBTH) and 3-dimethylaminobenzoic acid (DMAB). Ascorbate interference is eliminated by treating the urine sample with sodium nitrite prior to assaying. The assay is accurate (mean recovery of added oxalate in spiked urine sample is 93 +/- 11%), sensitive (detection limit 1.0 mumol/L), reproducible (within-batch CV 3.5%; between-batch CV 5%) and relatively rapid (15 samples/h). This assay correlates well (R = 0.99) with another established enzymatic method (using oxalate decarboxylase).
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PMID:Continuous-flow assay for urinary oxalate using immobilised oxalate oxidase. 403 68

Myeloperoxidase (MPO) is present at high levels in polymorphonuclear leukocytes (PMNs) and has been used as a marker to quantify the accumulation of PMNs in inflamed tissues. MPO activity in inflamed ocular tissues was inhibited by aspirates of aqueous humor. This inhibition could be duplicated by the addition of ascorbic acid at concentrations equivalent to those present in the aliquots of aqueous humor. Similarly, aqueous humor and ascorbic acid inhibited MPO from isolated rabbit leukocytes. Therefore, ascorbic acid appears to inhibit the functional activity of the peroxidase in PMNs, thus preventing potential tissue damage by this enzyme when released during leukocyte degranulation in inflammation. Ascorbic acid might fulfill a role as an endogenous anti-inflammatory agent in the eye.
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PMID:Ascorbic acid inhibits the activity of polymorphonuclear leukocytes in inflamed ocular tissues. 609 25

Polymorphonuclear leucocytes (PMN) are known to produce superoxide and other oxygen derivatives upon activation as part of their microbicidal armory. Here we report that extracellular ascorbate is effectively oxidised by activated but not by resting human PMN in vitro. The oxidation of ascorbate is mainly caused by the superoxide that is generated by the activated cells, as shown by its effective inhibition by superoxide dismutase. However, myeloperoxidase, which may generate hypochlorite, also contributes to a significant extent. Ascorbate reduces superoxide to peroxide, as indicated by measurements of the stoichiometry of ascorbate and oxygen consumption. These results support the notion that extracellular ascorbate may serve as an important physiological protecting agent against oxygen radical damage in inflammation.
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PMID:Activated polymorphonuclear leucocytes consume vitamin C. 609 56

Fibronectin and collagens are major constituents of the cell matrix of fibroblasts. Fibronectin is a 220,000 dalton glycoprotein that mediates a variety of adhesive functions of cells examined in vitro. Fibronectin is secreted in a soluble form and interacts with collagen to form extracellular filaments. Fibronectin and procollagen type I were localized using the peroxidase anti-peroxidase method. Under standard culture conditions, fibronectin and procollagen were localized to non-periodic 10 nm extracellular fibrils, the cell membrane and plasma membrane vesicles. Ascorbate treatment of cells leads to a new larger fibril with a diameter of approximately 40 nm. Antibodies to fibronectin and procollagen I react to these native collagen fibrils with an axial periodicity of approximately 70 nm. Fibronectin is clearly associated with native collagen fibrils produced by ascorbate treated cells and there is an asymetric distribution or segregation of fibronectin on these collagen fibrils with a 70 nm axial repeat.
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PMID:An axial periodic fibrillar arrangement of antigenic determinants for fibronectin and procollagen on ascorbate treated human fibroblasts. 616 Mar 20

Ascorbic acid (vitamin C) was found to stimulate the chlorinating activity of human myeloperoxidase (donor:hydrogen peroxide oxidoreductase, EC 1.11.1.7) 3-fold in vitro and to shift the pH optimum of the reaction to higher pH values. These effects are due to the conversion by ascorbic acid of inactive compound II formed during turnover into native enzyme.
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PMID:Vitamin C stimulates the chlorinating activity of human myeloperoxidase. 631 33


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