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: KEGG:D02259 (NaI)
1,823 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied whether eosinophil peroxidase (EPO), an eosinophil granule basic protein, can alter beta-adrenergic receptor (BAR) density on the guinea pig lung membrane. Lung membrane was first preincubated with 1-10 U/ml EPO and then incubated with 10(-4) M NaI and 10(-4) or 10(-6) M H2O2 for 2 hours. BAR density was determined using (-)125I-cyanopindolol. EPO combined with 10(-4) M H2O2 and I decreased the BAR density in a concentration-dependent manner. When only 10(-4) M H2O2 was used, the decrease in BAR density was small but significant. When compared to I, bromide was less effective and chloride alone was not effective. These results suggest that EPO is one of the factors responsible for beta-adrenergic blockade in asthma.
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PMID:Effect of eosinophil peroxidase on beta-adrenergic receptor density on guinea pig lung membrane. 133 76

Thyroid peroxidase (TPO), the major enzyme in the thyroid hormone synthesis, multifunctionally catalyzes (1) iodide oxidation, (2) iodination of the precursor protein, and (3) a coupling reaction of iodotyrosyl residues. The present study was carried out to examine the mercurial effects on the iodination, the second step of TPO. Purified porcine thyroglobulin or bovine serum albumin as acceptor protein was iodinated with [125I]NaI and H2O2 by purified porcine TPO. Iodinated protein was separated by acid precipitation on membrane filter or paper chromatography. Both CH3HgCl and HgCl2 dose-dependently inhibited the iodination, but HgCl2 was more potent to inhibit the iodination than CH3HgCl. These mercurial effects on the second step resemble the effects on the third step which were already reported; but are in marked contrast to the effects on the first step, where TPO was inhibited by HgCl2 but never by CH3HgCl.
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PMID:Differential effects of methylmercuric chloride and mercuric chloride on oxidation and iodination reactions catalyzed by thyroid peroxidase. 209 Jan

This study describes the effects of hydrogen peroxide on the two iodide transport systems, I influx and I efflux, in the cultured FRTL-5 rat thyroid cells. I influx was measured by the amount of I taken up by the cells during incubation with Na125I and NaI for 7 min, and I efflux was measured by calculating the rate of 125I release from the 125I-loaded cells in the presence and absence of 5 mmol/l H2O2. Exposure to greater than 100 mumol/l H2O2 for 40 min caused a significant inhibition of I influx; the inhibition was reversible and non-competitive with iodide. Thyroid Na+K+ ATPase activity, a major mechanism to drive I influx, decreased by 40% after the cells were exposed to 5 mmol/l H2O2 for 10 min. H2O2 enhanced I efflux only when Ca2+ was present in the medium. The mechanism of an enhanced I efflux by H2O2 appears to be mediated through the elevation of free cytosolic Ca2+ concentration. Our data indicate that H2O2 can affect I transport by inhibiting I influx and enhancing I efflux.
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PMID:Hydrogen peroxide inhibits iodide influx and enhances iodide efflux in cultured FRTL-5 rat thyroid cells. 216 23

The isomeric (17 alpha,20E)- and (17 alpha,20Z)-(iodovinyl)estradiol derivatives 3 and 6, and their no-carrier-added (nca) [125I]iodovinyl analogues, were tested for their relative target tissue retention and binding affinity for the estrogen receptor. The (iodovinyl)estradiols 3 and 6 were prepared via destannylation of the (17 alpha,20E)- and (17 alpha,20Z)-tributylstannyl precursors 2 and 4 with retention of configuration. Selective formation of the E or Z isomers 2 and 4 during the reaction of 17 alpha-ethynylestradiol 1a with tri-n-butyltin hydride was controlled by the presence or absence of the catalyst, the polarity of the solvent, and the reaction temperature. The nca [125I]iodovinyl analogues [125I]-3a and [125I]-6a were obtained in good radiochemical yield and high purity by treatment of 2a and 4a with [125I]NaI in the presence of H2O2 and chloroamine-T, respectively. Of the two isomeric iodovinyl derivatives 3 and 6, the 20Z isomer 6a exhibited the highest receptor binding affinity and the [125I]-6a gave the highest in vivo receptor-mediated target tissue uptake.
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PMID:Synthesis, receptor binding, and tissue distribution of (17 alpha,20E)- and (17 alpha,20Z)-21-[125I]iodo-19-norpregna-1,3,5(10), 20-tetraene-3,17-diol . 317 27

Ascaridole, an asymmetric monoterpene endoperoxide with anthelmintic properties, occurs as a major constituent (60-80%) in the volatile oil of American wormseed fruit (Chenopodium ambrosioides: Chenopodiaceae), and as a lesser component in the leaf pocket oil of the boldo tree (Peumus boldus: Monimiaceae). Determination of optical activity and chromatographic resolution of naturally occurring ascaridole, and several synthetic derivatives, showed that both wormseed and boldo produce ascaridole in racemic form. The biosynthesis of ascaridole from the conjugated, symmetrical diene alpha-terpinene (a major component of the oil from wormseed) was shown to be catalyzed by a soluble iodide peroxidase isolated from homogenates of C. ambrosioides fruit and leaves. The enzymatic synthesis of ascaridole was confirmed by capillary gas-liquid chromatography and mass spectrometry of the product, which was also shown to be racemic. Optimal enzymatic activity occurred at pH 4.0 in the presence of 2.5 mM H2O2 and 1 mM NaI. Soluble enzyme extracts were fractionated by gel filtration on both Sephacryl S-300 and Sephadex G-100, and were shown to consist of a high-molecular-weight peroxidase component (Mr greater than 1,000,000, 30% of total activity) and two other peroxidase species having apparent molecular weights of 62,000 and 45,000 (major component). Peroxidase activity was susceptible to proteolytic destruction only after periodate treatment, suggesting an association of the enzyme(s) with polysaccharide material. Ascaridole biosynthesis from alpha-terpinene was inhibited by cyanide, catalase, and reducing agents, but not by compounds that trap superoxide or quench singlet oxygen. A peroxide transfer reaction initiated by peroxidase-generated I+ is proposed for the conversion of alpha-terpinene to ascaridole.
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PMID:Biosynthesis of ascaridole: iodide peroxidase-catalyzed synthesis of a monoterpene endoperoxide in soluble extracts of Chenopodium ambrosioides fruit. 649 93

The antimicrobial oxidative system (myeloperoxidase (MPO), H2O2 and a halide) produced by stimulated PMNLs is simulated in vitro using horseradish peroxidase (HRP), H2O2 and NaI. Ascorbate, thiamine, levamisole and cysteine prevent and reverse the PMNL motility inhibiting effects of the HRP/H2O2/NaI system. The ability of these agents to protect the PMNL specifically from the known iodinating and oxidising abilities of this system was investigated. All four agents protect the PMNL from iodination by HRP/H2O2/NaI. However, only ascorbate and thiamine are able to reverse this process after it has occurred. Thiamine is seen on thin layer chromatography followed by autoradiography to be iodinated by this system. Ascorbate, thiamine and cysteine are able to protect the neutrophil sulfhydryl groups from oxidation by the system. One can therefore conclude that ascorbate and cysteine protect neutrophil motility from inhibition by the HRP/H2O2/NaI system by acting as reducing agents which maintain the neutrophil sulfhydryl groups. Thiamine also acts as a reducing agent, though not as effectively as ascorbate or cysteine. In addition, thiamine protects the PMNL from iodination by a competitive mechanism. The mechanism of levamisole protection is less clear but may involve scavenging of free radicals generated by the HRP/H2O2/NaI system. Protease enzymes, glycolysis and adherence are found not to be target sites for the PMNL motility inhibiting effects of the HRP/H2O2/NaI system. Further, increasing concentrations of the synthetic leukoattractant FMLP were shown to increase the auto-iodination of PMNLs without addition of extraneous peroxidase or peroxide. This data was compared with optimal FMLP concentrations for chemotaxis.
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PMID:Oxidative inhibition of polymorphonuclear leukocyte motility mediated by the peroxidase/H2O2/halide system: studies on the reversible nature of the inhibition and mechanism of protection of migratory responsiveness by ascorbate, levamisole, thiamine and cysteine. 665 35

Dihydropyrimidine dehydrogenase (DPDase) catalyzed the debromination of 5-bromo-5,6-dihydrouracil (BrUH2) to uracil at pH 7.7 and 37 degrees C. The debrominating activity of DPDase was increased 5-fold by treatment with H2O2, whereas the dehydrogenating activity was inhibited by this treatment. The time course for increasing the debrominating activity by H2O2 was similar to that for decreasing the dehydrogenating activity. Thus, the relative amounts of debrominating and dehydrogenating activities of DPDase were reciprocally related. H2O2 treatment of DPDase decreased the number of thiol groups reactive with 5,5'-dithiobis(2-nitrobenzoate) from eight/subunit to less than one. The kcat for debromination of BrUH2 by H2O2-treated DPDase (OxDPDase) was 1.9 s-1, which was comparable with kcat for reduction of thymine (2.1 s-1) by DPDase. Even though the debromination of BrUH2 to uracil does not involve a net reduction of BrUH2, NADPH was required for this activity. The reaction of OxDPDase with 5-iodo-5,6-dihydrouracil (IUH2) was more complicated than that with BrUH2. Aerobically, OxDPDase catalyzed the deiodination of IUH2 to uracil and the iodination of NADPH to 5-iodo-6-hydroxy-1,4,6-trihydronicotinamide adenine dinucleotide phosphate. The turnover number for the iodination reaction was enhanced by NaI and had a value of 3.5 s-1 in the presence of 4 mM IUH2 and 50 mM NaI. Anaerobically, OxDPDase catalyzed the above reactions, the deiodination of IUH2 to 5,6-dihydrouracil, and the hydration of NADPH to 6-hydroxy-1,2,3,4-tetrahydronicotinamide adenine dinucleotide phosphate. The turnover number for the anaerobic hydration of NADPH was similar to that for the aerobic iodination of NADPH.
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PMID:Dehalogenating and NADPH-modifying activities of dihydropyrimidine dehydrogenase. 792 74

To develop androgen and progesterone receptor-based radioligands for SPECT imaging we synthesized several radioiodinated 17 alpha-iodovinyl testosterone and 19-nortestosterone analogs and evaluated their biological properties. The synthesis of these compounds proceeds via the (17 alpha,20E/Z)stannyl intermediates and involves addition of tri-n-butyltin hydride to the 17 alpha-ethynyl group of the steroid using either azobisiso butyronitrile or triethylborane as a catalyst. The stannyl derivatives are stereospecifically converted to the corresponding (17 alpha,20E/Z)iodovinyl derivatives using molecular iodine, or to the [125I]iodovinyl analogs using [125I]NaI and H2O2. Androgen and progesterone receptor (AR and PgR) binding affinities were measured via a competitive in vitro binding assay. In general 19-nortestosterone derivatives showed higher receptor affinities as compared to the testosterone derivatives. In the latter series the highest PgR binding affinities were observed with the (17 alpha,20Z)iodovinyl-19-nortestosterone (IVNT) (92 vs 100 for R5020) followed by the 7 alpha-methyl analog, whereas the highest AR binding affinity was observed with the 7 alpha-Me-(17 alpha,20Z)IVNT (54 vs 100 for 5 alpha-dihydrotestosterone). These derivatives were also labeled with 125I and evaluated for their in vivo target organ uptake (prostate and estrogen-primed uterus). The highest PgR-mediated target tissue uptake was observed with the (17 alpha,20Z)-[125I]IVNT and its 7 alpha-methyl derivatives whereas only one derivative, the 7 alpha-Me-(17 alpha,20Z)-[125I]IVNT, showed AR-mediated dorsal prostate retention. Although some of the IVNT derivatives have interesting binding properties, the lack of in vivo selectivity does suggest that the 123I-labeled analogs are unlikely to be suitable for imaging of AR and PgR-rich tissues.
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PMID:Synthesis of (17 alpha,20E/Z)iodovinyl testosterone and 19-nortestosterone derivatives as potential radioligands for androgen and progesterone receptors. 800 36

Cefdinir, a new oral 2-amino-5-thiazolyl cephalosporin, inhibited the luminol-amplified chemiluminescence (LACL) response of human neutrophils stimulated by PMA but not opsonized zymosan, in a concentration-dependent but not time-dependent manner. The LACL response to opsonized zymosan in cytochalasin B-treated neutrophils was, however, inhibited by cefdinir. Various cephalosporins, regardless of the presence of a 2-amino-5-thiazolyl moiety, did not significantly alter the neutrophil LACL response triggered by PMA and zymosan. The LACL response induced by the calcium ionophore A23187 and FMLP was also impaired by cefdinir, and this impairment was increased in cytochalasin B-treated neutrophils. Superoxide anion generation by neutrophils, measured in terms of lucigenin-amplified chemiluminescence and cytochrome c reduction, was not altered. Spontaneous and FMLP-induced neutrophil degranulation, assessed by lysozyme and beta-glucuronidase release, were not modified by cefdinir. Furthermore, cefdinir inhibited LACL generation in cell-free systems consisting of H2O2, NaI, and either horseradish peroxidase or a myeloperoxidase-containing neutrophil extract. Orthodianisidine oxidation in these two acellular systems was inhibited by cefdinir. Cefdinir did not alter neutrophil bacterial killing at concentrations that inhibited myeloperoxidase-containing neutrophil extract-dependent reactions induced by soluble stimuli. Taken together, these data strongly suggest that cefdinir directly inhibits the activity of myeloperoxidase-containing neutrophil extract released into the extracellular medium during neutrophil stimulation by soluble mediators, but has no effect on that released into the phagolysosome during phagocytosis. This unusual property of a member of the beta-lactam family could be of interest in modulating the exaggerated inflammatory process often associated with infectious diseases.
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PMID:Cefdinir (CI-983), a new oral amino-2-thiazolyl cephalosporin, inhibits human neutrophil myeloperoxidase in the extracellular medium but not the phagolysosome. 813 56

Thyroid peroxidase (TPO) is well known to be an essential enzyme for the biosynthesis of thyroid hormone. The changes of TPO activities in thyroid tissue have already been reported in pathophysiological and experimental conditions by several assay methods. Most of these assay methods, however, need relatively large amounts of tissue (over 10mg wet tissue) to obtain enzyme fraction for assay by homogenization and fractionation of the tissue. Therefore, it is difficult to apply these methods to relatively small numbers (less than 10(6) cells) of thyroid cells. In the present study, we attempted to develop a new and simple method for the assay of TPO activity using tetramethylbenzidine (TMB) as substrate. The reaction mixture were composed of 250 microliters of commercially available tetramethylbenzidine solution containing H2O2 (TM-Blue; TSI-CDP) and 250 microliters of cell lysate obtained by freeze-thawing in 0.1M citrate buffer (pH 4.8). Various doses of known amounts of horseradish peroxidase (HRP; 0-1000 microU) were assayed as a standard at the same time. TPO activity in cell lysate was expressed as the activity corresponding to HRP activity. In this assay method, TPO activity of sonicated-cell lysate was higher than that of nonsonicated-cell lysate, and the activity in sonicated cell lysate was linearly correlated with cell numbers. Next, the effects on the TPO activity of the direct addition of various agents into the reaction mixture were also examined. Both methylmercaptoimidazole (MMI) and NaN3 strongly inhibited TPO activity in sonicated-cell lysate as well as in mitochondria-microsomal fraction of thyroid tissue with the respective IC50 value of less than 5 microM and less than 0.1 mM. In the present method, the authors could demonstrate the following: 1) After 4 days of suspension culture with TSH (0.5 mU/ml), TPO activity of the follicles increased 3.2-5.6 fold when compared with that cultured in the absence of TSH. 2) (Bu)2cAMP (DBC; 1 mM) and forskolin (20 microM) also increased TPO activity of the follicles by 2.9-5.2 and by 2.9-6.2 fold. 3) The addition of NaI (0-100 microM) into medium dose-dependently inhibited the induction of TPO activity by TSH. 4) EGF (10(-8) M) and PMA (10(-6) M) as well as NaI (100 microM) also inhibited the induction of TPO activity in the follicles by TSH, DBC and forskolin during culture for 4 days. Accordingly, it is indicated that these agents may inhibit an induction of TPO activity at least in part at the step of post-cAMP.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[A simple assay of peroxidase activity in cultured thyroid follicles using tetramethylbenzidine as substrate]. 833 Jun 56


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