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)

Myeloperoxidase with an A420/280 ratio of 0,48 was prepared from normal human leucocytes. This partially purified preparation catalysed guaiacol oxidation, iodination of bovine serum albumin and de-iodination of 125I-thyroxine. Non-steroidal anti-inflammatory drugs (naproxen, indomethacin and flufenamic acid) showed a significant inhibitory effect on myeloperoxidase-catalysed iodination at concentrations of 10(-4)M and higher. Guaiacol also inhibited myeloperoxidase-catalysed iodination, and its iodination inhibition curve was nearly identical to that obtained with the anti-inflammatory drugs. At concentrations between 10(-3)M and 10(-7)M the antiinflammatory drugs had very little or no effect on thyroxine de-iodination. Flufenamic acid and indomethacin, however, inhibited de-iodination significantly at a concentration of 10(-2)M. It is postulated that non-steroidal anti-inflammatory drugs may inhibit myeloperoxidase-catalysed protein iodination by acting as oxidizable cofactors which compete with other oxidizable substrates for oxidants formed by the peroxidase-hydrogen peroxide complex. In view of this and because the myeloperoxidase-hydrogen peroxide system may be involved in inflammatory tissue damage, the possibility should be considered that the action of non-steroidal anti-inflammatory drugs is at least partly attributable to a radical scavenging effect or to sequestration of oxidants.
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PMID:Inhibitory effects of non-steroidal anti-inflammatory drugs on human myeloperoxidase. 22 74

Hydrogen peroxide-dependent oxidation of xenobiotics in a crude fraction of human term placental membranes (nuclei, mitochondria and microsomes) was investigated. Guaiacol was employed as a model substrate. The rate of its oxidation was found to be dependent on the concentration of protein, H2O2 and the substrate as well as the pH of the buffer. Several other classical substrates for peroxidases from different sources viz. pyrogallol, benzidine, p-PDA, DMBD, ABTS, TMPD and TMBD and endogenous chemicals such as bilirubin and epinephrine were also found to undergo oxidation. The xenobiotic oxidizing capacity of the membranes was retained by CaCl2 (0.5 M) extract as well as by the partially purified enzyme obtained by affinity (Con A) chromatography. The H2O2-dependent chemical oxidation by the partially purified peroxidase was inhibited by NaN3 and KCN (IC50 values 41 and 23 microM respectively). These results suggest that peroxidase may be a major enzyme in human term placenta capable of oxidation of endogenous chemicals and xenobiotics.
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PMID:Peroxidase: a novel pathway for chemical oxidation in human term placenta. 129 5

Guaiacol peroxidase from spinach catalyzes the oxidation of p-aminophenol to produce the aminophenoxy radical as the primary product which is converted further into a stable oxidation product with an absorption peak at 470 nm. The p-aminophenol radicals oxidize ascorbate (AsA) to produce monodehydroascorbate radicals. Kinetic analysis indicates that p-aminophenol radicals also oxidize monodehydroascorbate to dehydroascorbate. Incubation of AsA peroxidase from tea leaves and hydrogen peroxide with p-aminophenol, p-cresol, hydroxyurea, or hydroxylamine results in the inactivation of the enzyme. No inactivation of the enzyme was found upon incubation of the enzyme with these compounds either in the absence of hydrogen peroxide or with the stable oxidized products of these compounds. The enzyme was protected from inactivation by the inclusion of AsA in the incubation mixture. The radicals of p-aminophenol and hydroxyurea were produced by AsA peroxidase as detected by their ESR signals. These signals disappeared upon the addition of AsA, and the signal characteristic of monodehydroascorbate was found. Thus, AsA peroxidase is inactivated by the radicals of p-aminophenol, p-cresol, hydroxyurea, and hydroxylamine which are produced by the peroxidase reaction, and it is protected from inactivation by AsA via the scavenging of the radicals. Thus, these compounds are the suicide inhibitors for AsA peroxidase. Isozyme II of AsA peroxidase, which is localized in chloroplasts, is more sensitive to these compounds than isozyme I. In contrast to AsA peroxidase, guaiacol peroxidase was not affected by these various compounds, even though each was oxidized by it and the corresponding radicals were produced.
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PMID:Hydroxyurea and p-aminophenol are the suicide inhibitors of ascorbate peroxidase. 215 59

Peroxidase activity was partially purified from neonatal (3 to 6 days old) rat skin. The membrane-bound peroxidase activity was extracted with 0.5 M calcium chloride and was monitored spectrophotometrically at 470 nm with 2-methoxyphenol (guaiacol) and hydrogen peroxide as substrates. Subcellular distribution studies indicated the activity to be highest and comparable in nuclei and mitochondria, lowest in microsomes, and absent in cytosol. The peroxidase activity was partially purified by affinity chromatography on concanavalin A-sepharose 4B and by gel filtration using Bio-Gel P-150. Purification factors from these two steps were about 25 and 4, respectively. Peroxidase extraction in the presence of 2 mM N-ethylmaleimide increased activity about twofold. The combination of 2 mM N-ethylmaleimide and 10% (w/v) glycerol was found to be optimal for preservation of activity. Peroxidase activity increased linearly with increases in protein concentration, time, and guaiacol concentration. Activity was inhibited approximately 75% by 0.1 mM potassium cyanide or 0.05 mM sodium azide. Pyrogallol, hydroquinone, p-cresol, catechol, benzidine, 3,3'-dimethoxybenzidine, tetramethylbenzidine and p-phenylenediamine also acted as substrates for the rat cutaneous peroxidase.
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PMID:Peroxidase, an alternate pathway to cytochrome P-450 for xenobiotic metabolism in skin: partial purification and properties of the enzyme from neonatal rat skin. 285 75

Previous studies have shown that phenylbutazone, another pyrazolone, inhibits thyroid peroxidase activity and interferes with iodide organification. We have developed "in vitro" studies with rat particulated peroxidase and lactoperoxidase (LPO) to study the effects of dipyrone upon thyroid peroxidase and to determine the type of inhibition. The 3-monoiodothyrosine (MIT) and 3,5-diiodothyrosine (DIT) synthesis was markedly affected by 6 X 10(-4) M dipyrone with inhibitions of 59% and 30% respectively. No difference was observed with lower concentrations. Inhibition of peroxidase activity (Triiodide assay) was found when crude rat peroxidase preparations and LPO were incubated with dipyrone in concentrations ranging from 10(-3) M to 10(-8) M, with a Ki of 2.5 X 10(-5) M and 4 X 10(-5) M respectively. Guaiacol peroxidation was scarcely affected by the action of the drug; 10(-3) M produced inhibition of 50%. Line weaver-Burk: plots were used to investigate the inhibition of LPO activity by dipyrone. The inhibition by the drug was competitive with the iodide. We may conclude that dipyrone and other drugs of the pyrazolone group act upon peroxidase activity "in vitro", by an inhibition of competitive type and in presence of iodide.
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PMID:Inhibitory action of dipyrone on rat thyroid peroxidase and lactoperoxidase activities. 293 10

Guaiacol peroxidase (G-Px) is an enzyme which in the human uterine epithelium has been found to be inhibited in vitro by estrogens and especially catecholestrogens. This study determines if the concentration of G-Px would vary inversely to plasma estrogens. It is hoped that this enzyme would decrease sufficiently early before ovulation to be useful as a simple predictor of ovulation in women. G-Px was serially measured in cervical mucus during the menstrual cycle of 5 healthy volunteers. Radioimmunoassay measured the following hormones in the plasma samples: 17 beta-estradiol, progesterone, luteinizing and follicle stimulating hormones. In the midcycle, G-Px levels decreased 20- to 100-fold relative to other times of the cycle, the decrease coinciding with the peak of plasma estrogens and probably causally related to them. G-Px levels were not affected by the 2nd peak of plasma estrogens, possibly because of the counter effect of progesterone. Further research should be done to determine possible hormonal control of G-Px activity. G-Px may be central to the structure and function of cervical mucus. They may have bactericidal and spermicidal properties and may play a role in sperm capacitation. The findings in this study may be beneficial in estimating optimal time for intercourse and artificial insemination in infertile patients and improving the efficacy of the periodic abstinence method of contraception by easily identifying the fertile period. In addition, the G-Px assay in cervical mucus is adaptable to a simple sensitive home test because the products of guaiacol oxidation are visible to the naked eye and drastic changes in color production can be easily perceived.
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PMID:Guaiacol peroxidase levels in human cervical mucus: a possible predictor of ovulation. 627 63

Guaiacol peroxidase (G-Px) was measured in extracts from five sections along the length of human uterus on different days of the menstrual cycle or after menopause. The lower uterine-endocervical region had a significantly higher G-Px content (expressed as enzyme units per g wet tissue) than the other sections, although in postmenopausal patients the G-Px activity was uniformly low in all sections of the uterine cavity. We observed no significant changes in G-Px levels during the menstrual cycle, except, possibly, a decrease around ovulation, which precluded a positive correlation between plasma estrogen levels and uterine G-Px content; such estrogen dependence of G-Px has been previously shown in the rat. In vitro, G-Px was inhibited by estriol and 17 beta-estradiol, marginally inhibited by estrone, and most notably inhibited by the catecholestrogens tested (2-hydroxy-17 beta-estradiol, 2-hydroxy-estriol, and 2-hydroxy-estrone), which were equipotent inhibitors; LH and FSH, progesterone, or cortisol had no effect on G-Px activity. We hypothesize that catecholestrogens are natural substrates and regulations of G-Px activity in the human uterus.
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PMID:Distribution of guaiacol peroxidase in human endometrium and endocervical epithelium during the menstrual cycle. 627 87

The cellular content of myeloperoxidase (MPO), chymotrypsin-like cationic protein (CCP) and lactoferrin (LF) of isolated polymorphonuclear leucocytes (PMNs) from pregnant women were analysed by immuno-chemical methods. The cellular levels of MPO and CCP were unaltered during pregnancy while the cellular levels of LF were increased during pregnancy and post partum (P less than 0.01). Peroxidase activity within isolated PMN was analysed by two methods, a Guaiacol method and a Chemiluminescence method. The activity was found to be reduced during pregnancy. The reduction was explained by the reduction in eosinophil peroxidase which in turn was a consequence of a reduced number of circulating eosinophils during pregnancy.
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PMID:The peroxidase activity and cellular content of granule proteins in PMN during pregnancy. 632 31

Resonance Raman scattering from cow milk lactoperoxidase (LPO) and its complexes with various electron donors and inhibitors was investigated. The Raman spectrum of LPO is strikingly close to that of hog intestinal peroxidase but distinctly dissimilar to that of horseradish peroxidase (HRP). The v10 frequency suggested the six-coordinate high-spin structure of heme for native LPO in contrast with the five-coordinate high-spin structure for HRP. For the v10 band, benzohydroxamic acid caused a frequency shift with HRP but not with LPO. Guaiacol, o-toluidine, and histidine brought about a frequency shift of the v4 mode for LPO but not for HRP. The frequency shift was restored upon removal of the substrate or inhibitor by dialysis. The down shift of the v4 frequency is considered to represent an appreciable donation of electrons from the substrate or inhibitor to the porphyrin LUMO and thus their direct interaction with the heme group. From the relative intensity of the shifted and unshifted v4 lines, the dissociation constant was determined to be Kd = 52 mM for guaiacol and Kd = 87 mM for histidine at pH 7.4. The binding of histidine was relatively retarded in the presence of sulfate anion (Kd = 150 mM for 0.53 M sulfate present), and imidazole alone yielded no frequency shift, indicating the binding of the carboxyl group of histidine to the protein cationic site on one hand and a weak charge-transfer interaction between the imidazole group and the heme group on the other.
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PMID:Distinct heme-substrate interactions of lactoperoxidase probed by resonance Raman spectroscopy: difference between animal and plant peroxidases. 687 Nov 62

Studied for measuring the peroxidase activity from thyroid gland have usually been achieved on the basis of the H2O2 oxidation of I- to I3- catalyzed by peroxidase. The activity assay has been found to depend on several factors such as the relative order of reagent addition, protein content of the enzyme preparation, presence of detergent and the pH of the reaction medium. At below 7.0 pH, the contribution of the non-enzymic transformation of I- to total activity became quite significant, to the extent that at below 6.5 pH, the chemical reaction predominates over the enzymic one. At values above 7.0 pH, a very rapid decomposition of the product was observed. Guaiacol oxidation has been considered to be a more reliable method than the iodide one, especially when the substrate concentration and temperature vary, and when the activity of relatively rich in protein samples, as well as of some other substances that might interfere with the I3- formation, are going to be measured.
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PMID:Some limitation in the use of the I- method for measuring the peroxidase activity from bovine thyroid gland. 732 96


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