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)

1. Inhibition of myeloperoxidase (MPO)-catalyzed reactions by methyl-substituted xanthines has been investigated. 2. Except for theobromine and caffeine, all xanthines tested were potent inhibitors of the MPO-H2O2-Cl- system. 3. In contrast to methyl substitution in the 1 or 8 position of xanthine, substitution in the 3 or 7 position had a marked effect on the inhibition of MPO catalysis. 4. Two different inhibitory mechanisms were induced; scavenging of hypochlorous acid (HOCl) generated by the MPO system and accumulation of Compound II (ferryl MPO) which is inactive as a catalyst of Cl- oxidation.
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PMID:Interaction of methyl-xanthines with myeloperoxidase. An anti-inflammatory mechanism. 131 56

Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. Green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.
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PMID:Green tea composition, consumption, and polyphenol chemistry. 161 95

Wet heat shock (60 degrees C, 90 s) and caffeine (3.8 X 10(-4) M) afford significant radioprotection against post-irradiation O2-dependent damage which develops in seeds of approximately 3.5% moisture content. The damage was assessed in terms of seedling injury on the eighth day of growth. An increase in seedling injury is clearly seen, associated with a parallel increase in the peroxidase activity. There is a concomitant decrease in the content of total peroxides. Both these post-irradiation treatments potentiate the O2-independent component of seedling injury, irrespective of the seed moisture content. Analysis of the peroxidase activity in the seedlings using non-denaturing polyacrylamide gel electrophoresis reveals that two additional bands appear with the post-irradiation oxic damage. Radioprotection against this damage by caffeine, heat shock and O2-free post-irradiation hydration is accompanied by the disappearance of these two additional bands. However there is no appearance of the two additional bands in the peroxidase family even though the enzyme activity is substantially increased due to the action of caffeine and/or heat shock on the post-irradiation O2-independent pathway of damage. The probable mechanisms of radioprotection are discussed in this paper.
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PMID:Biochemical effects of heat shock and caffeine on post-irradiation oxic and anoxic damage in barley seeds of low and high water content. 167 40

Dry (approximately 3.5 and 4.0 per cent moisture content) barley seeds were exposed to 350 Gy of 60Co- gamma-rays in vacuo and post-hydrated at 4 degrees C for 8 h in O2-, N2-, or N2O-saturated water. The effect of caffeine and t-butyl alcohol (t-BuOH) dissolved in the post-hydration medium on the magnitude of damage developing under these three different gaseous circumstances was studied. The post-irradiation damage and its modification by caffeine and t-BuOH was assessed in terms of 8-day-old seedling injury, peroxidase activity and total peroxides in the 8-day-old seedlings. Post-irradiation O2-saturated hydration caused maximal 8-day-old seedling injury, and increased peroxidase activity with concomitant reduction in total peroxides. Both caffeine and t-BuOH afforded significant radioprotection against post-irradiation O2-dependent damage. Post-irradiation N2O-saturated hydration was even more significantly radioprotective than the N2-saturated post-hydration. Under these circumstances, t-BuOH exerted no effect whatsoever on the N2- and N2O-mediated post-irradiation damage. Caffeine, on the other hand, significantly potentiated these two components of damage. A brief consideration of the physicochemical events which possibly account for the observed effects is presented.
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PMID:Barley seed radiosensitivity following post-hydration in oxygen-, nitrogen- and nitrous oxide-saturated water. I. Influence of caffeine and t-butyl alcohol. 221 88

A competitive enzyme-linked immunosorbent assay suitable for the measurement of caffeine in plasma and serum has been developed. Sheep immunised with an immunogen prepared by coupling 7-(5-carboxypentyl)1,3-dimethylxanthine to egg albumin produced antibodies with little crossreactivity with the metabolites of caffeine. The enzyme label was prepared by coupling 7-(5-carboxypentyl)-1,3-dimethylxanthine to peroxidase using the mixed anhydride method. The assay, which has a sensitivity of 0.01 mumol/l, permits direct measurement of caffeine in plasma and serum samples. 50 plasma samples measured by ELISA and by an established radioimmunoassay showed a correlation of r = 0.97 (P less than 0.001).
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PMID:Development of an enzyme-linked immunosorbent assay for caffeine. 235 34

Methylxanthines are best known as phosphodiesterase inhibitors that cause a rise in intracellular cAMP. One would expect the two methylxanthines, caffeine and pentoxifylline, to have similar actions on neutrophils (PMN). However, caffeine stimulated and pentoxifylline inhibited PMN oxidative activity. Micromolar concentrations of pentoxifylline decreased native and recombinant tumor necrosis factor-alpha (TNF alpha)-primed formyl met-leu-phe (fMLP)-stimulated PMN chemiluminescence, superoxide production and myeloperoxidase (MPO) release. In contrast, equal concentrations of caffeine increased chemiluminescence and MPO release with no effect on superoxide production. These activities of the methylxanthines were only observed in the presence of physiological concentrations of adenosine, and were abolished by the treatment of the PMN with adenosine deaminase. The activities of adenosine, pentoxifylline and caffeine on PMN activity could not be readily explained by changes in PMN [cAMP]. Thus for TNF alpha-primed PMN, pentoxifylline decreases PMN activity by enhancing the effect of adenosine on degranulation and superoxide production; whereas caffeine increases PMN activity by counteracting the effect of adenosine on degranulation.
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PMID:Methylxanthines with adenosine alter TNF alpha-primed PMN activation. 865 88

Amine oxidation reactions are catalyzed by cytochrome P450 (P450) and peroxidase enzymes; both types of enzymes appear to function via aminium radical intermediates. N-Dealkylation is favored over N-oxygenation for secondary and tertiary amines with both kinds of enzymes, but in the peroxidase-like enzymes N-oxygenation is even less favorable because of apparent restriction of the Fe-O complex in the active site. Among the rat liver P450s many of the carcinogenic primary arylamines and heterocyclic amines are N-oxygenated by P450 1A2 to form the N-hydroxy arylamine derivatives. Studies with human liver P450s also indicate that P450 1A2 plays a major role in such reactions, although some arylamines such as 4,4'-methylene-bis (3-chloroaniline) and dapsone are preferentially N-oxygenated by P450 3A4. Caffeine N3-demethylation has been developed as a useful marker of P450 1A2 levels in humans; the knowledge that P450 1A2 is the major phenacetin O-deethylase also allows insight into previous human interaction studies. 2-Ethynylnaphthalene is a useful mechanism-based inactivator of rat and rabbit P450 1A2 but not human P450 1A2 enzymes; the peptides labeled in the enzymes have been identified, along with the region in rat P450 1A2 that is modified with the photoaffinity label 4-azidobiphenyl. Microcrystals of rabbit P450 1A2 have been obtained as a first course to realizing the three-dimensional structures of these enzymes. Evidence is also presented that the major C8-guanyl DNA adducts resulting from these arylamines and heterocyclic amines in DNA may be formed via rearrangement of an initial N7-guanyl-2-arylamine adduct: reaction of N-acetoxy-2-aminofluorene with C8-methylguanine derivatives led to the formation of stable N7-substituted species, and reaction of N-acetoxy-2-aminofluorene with C8-bromoguanine yielded N-(C8-guanosinyl)-2-aminofluorene in a reaction best rationalized by such a mechanism.
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PMID:Mechanisms of cytochrome P450 1A2-mediated formation of N-hydroxy arylamines and heterocyclic amines and their reaction with guanyl residues. 884 98

Cysteine (an aminothiol) is known to protect against radiation damage, and is understood to do so by generating hydrogen peroxide which subsequently inhibits RNA synthesis. Our results showed inability of catalase to remove or reduce the magnitude of radioprotection by caffeine and/or cysteine at optimal/suboptimal temperatures in barley. This observation was adequately corroborated by data on frequency of chromosomal aberration, peroxidase activity and total protein content. On the contrary, catalase tended to enhance the radioprotective effectiveness of cysteine. Macromolecular synthetic patterns in caffeine and/or cysteine treated embryos were too inconsistent to permit a logical conclusion with regard to their positive involvement in the biochemical pathway of chemical modification of radiation damage. On the other hand, mutually annihilatory reaction hypothesis based on physico-chemical principles provides a satisfactory explanation for the observed effects.
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PMID:Probing tenability of biochemical vis-a-vis physicochemical interpretations of modulation of radiation damage by caffeine and cysteine in barley. 902 19

During investigations on the effect of caffeine on ibuprofen-induced gastric mucosal lesions in rats, we have found that caffeine (p.o.) inhibits the development of ibuprofen-induced gastric lesions in a dose-dependent manner (ED50 18.4 mg kg(-1)). To investigate this protective effect of caffeine, we have studied the effect of caffeine on HCl-ethanol-induced gastric mucosal lesions with or without indomethacin pretreatment. Caffeine inhibited the development of HCl-ethanol-induced gastric lesions with and without indomethacin pretreatment. These results indicate that caffeine did not act as a mild irritant but, on the contrary, had protective effects. We measured the gastric mucosal prostaglandin E2 (PGE2) concentrations and gastric mucosal blood flow, as representative protective factors for gastric mucosa. Caffeine did not affect the gastric mucosal PGE2 concentrations 4h after administration of ibuprofen. However, topical administration of caffeine resulted in an increase in gastric mucosal blood flow, as measured by laser Doppler flowmetry. We investigated the gastric acid secretion and gastric mucosal myeloperoxidase activity as representative aggressive factors for gastric mucosa. When caffeine was administered intraduodenally in pylorus-ligated rats, gastric acid secretion decreased in a dose-dependent manner, with an ED50 of 44.9 mg kg(-1). Caffeine decreased ibuprofen-induced gastric myeloperoxidase activity in a dose-dependent manner, with an ED50 of 9.1 mg kg(-1). These findings indicate that caffeine, at least in rats, may inhibit the development of acute gastric mucosal injury. The mechanisms underlying the protective actions of caffeine are unclear, but may be related in part to an increase in gastric mucosal blood flow and suppression of neutrophil activation.
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PMID:Effect of caffeine on ibuprofen-induced gastric mucosal damage in rats. 1046 57

Free radicals are involved in diverse disorders such as tumoral, central nervous system alterations, immunological and inflammatory pathologies. Peroxidase is an oral enzyme involved in the defense of the oral cavity. Ilex species such as Ilex paraguariensis St. Hil. and the commercial product made with it "Yerba Mate" are used traditionally as antirheumatics and for the treatment of gastrointestinal diseases among others and also as a beverage with nutritional and stimulant properties. The presence of polyphenolic derivatives and flavonoids in the aqueous extract has been determined by HPLC analysis. In this study, the activity of aqueous extracts of I. paraguariensis and "Yerba Mate" on peroxidase secretion in female rat submandibular glands was investigated. The contribution to this pharmacological activity by some major hydrocynnamic acid derivatives present in the crude extracts, such as chlorogenic acid and caffeic acid and the most abundant methylxanthine, caffeine, was also evaluated. Spectrophotometrical determination of peroxidase activity showed that both extracts produced a significant increase in both secreted peroxidase and total peroxidase activity, though "Yerba Mate" showed a higher activity (EC(50) "Yerba Mate": 148+/-10 microg/ml; EC(50)I. paraguariensis: 841+/-20 microg/ml). The HPLC/DAD analysis of the crude extracts was performed and chlorogenic acid, caffeic acid and caffeine were identified and quantified. The results (expressed as W/W percentage of dried material) were as follows: I. paraguariensis: chlorogenic acid: 2.80+/-0.30, caffeic acid: 0.023+/-0.004, caffeine: 1.06+/-0.06; "Yerba Mate": chlorogenic acid: 1.98+/-0.37; caffeic acid: 0.020+/-0.003, caffeine: 0.70+/-0.06. Caffeine and chlorogenic acid were proved to play an important role in the induction of peroxidase secretion induced by the extracts.
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PMID:Effect of Ilex extracts and isolated compounds on peroxidase secretion of rat submandibulary glands. 1714 90


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