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)

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

The role of various enzymes and biological molecules on the activation and deactivation of the metabolites of phenol was investigated in vitro. Phenol, the major metabolite of benzene, is metabolized to hydroquinone and catechol. Activation of these metabolites and deactivation of their oxidized forms was assessed by the amount of covalent binding to microsomal protein. [14C]Phenol and NADPH were incubated with hepatic microsomes isolated from phenobarbital-pretreated guinea pigs, and 2.33 nmoles of hydroquinone and 0.12 nmole of catechol were formed per minute per milligram of microsomal protein. Covalent binding of the metabolites to microsomal protein incubated with microsomes isolated from guinea pigs pretreated with phenobarbital was 252 pmoles bound/min/mg; with microsomes from untreated guinea pigs, covalent binding was 146 pmoles bound/min/mg. Covalent binding was inhibited greater than 90% with the addition of N-octylamine, ascorbate, or GSH. The addition of superoxide dismutase inhibited covalent binding with microsomes isolated from phenobarbital-pretreated guinea pigs 35% but did not inhibit it with microsomes isolated from untreated animals. Partially purified guinea pig hepatic DT-diaphorase [NAD(P)H (quinone acceptor) oxidoreductase, EC 1.6.99.2] inhibited covalent binding 70%. This effect was reversed in the presence of dicumarol, a specific inhibitor of DT-diaphorase. DT-diaphorase present in the 10(5) X g supernatant fraction was also active in inhibiting covalent binding but only after the removal of endogenous reduced glutathione. This effect could also be reversed by dicumarol. The addition of diaphorase (NADH:lipoamide oxidoreductase, EC 1.6.4.3) partially purified from Clostridium kluyveri inhibited covalent binding 86%. The addition of hydrogen peroxide and horseradish peroxidase (peroxidase, EC 1.11.17) or myeloperoxidase(s) increased covalent binding 30-fold and 6-fold, respectively. Ascorbate decreased this binding greater than 95%. These results indicate that hydroquinone, catechol, and phenol as well as their oxidized forms can be activated or deactivated by several of the above model systems. These systems may play a role in the myelotoxicity of benzene by modulating covalent binding.
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PMID:DT-diaphorase and peroxidase influence the covalent binding of the metabolites of phenol, the major metabolite of benzene. 674 27

We describe the enzymic determination of free fatty acids in serum with use of acyl-CoA synthetase (EC l.2.1.3), acyl-CoA oxidase (no EC no. assigned) and peroxidase (EC 1.11.1.7). The free fatty acids are activated by acyl-CoA synthetase in the presence of ATP and coenzyme A. The acyl-CoA formed is oxidized by acyl-CoA oxidase to enoyl-CoA with simultaneous production of hydrogen peroxide, which is oxidatively coupled with 4-amino-antipyrine and 2,4-dibromphenol in the presence of peroxidase to yield a product that absorbs maximally at 505 nm. Standard curves prepared with various kinds of fatty acids are linear to at least 2.0 mmol/L and are practically congruent. Ascorbic acid or bilirubin interferes slightly. Results by the present method correlate well with those by the colorimetric method involving 2-(2-thiozolylazo)-p-cresol (r = 0.98). Replicate analyses of standard solution and of two kinds of control sera demonstrated the following between-assay precision: mean absorbance 0.224 (SD 0.002), CV 0.85%; mean concentration, 326 (SD 7.3) and 1076 (SD 22.7) mumol/L, CV 2.24 and 2.11%, respectively.
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PMID:Enzymic determination of free fatty acids in serum. 677 37

Prostaglandin synthase catalyzes the oxidation of arachidonic acid to prostaglandin H2 via a hydroperoxide intermediate, prostaglandin G2. The prostaglandin synthase system cooxidizes 3,5,3'5'-tetramethylbenzidine (TMB), a derivative of the human carcinogen benzidine, to colored products. This process is arachidonic acid dependent and indomethacin sensitive. The reaction is also supported by hydroperoxides, and, in this case, indomethacin has no effect. This suggests that the cooxidation is mediated by the hydroperoxidase activity of prostaglandin synthase. The products of TMB oxidation by this system are the same as those obtained with lactoperoxidase and H2O2 or with horseradish peroxidase and H202. The initial products of TMB oxidation are the TMB radical cation and a charge-transfer complex composed of TMB and its two-electron (diimine) oxidation product. The TMB radical cation was identified by electron spin resonance spectroscopy. Ascorbic acid reduces the products, regenerating the parent compound.
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PMID:Cooxidation of the clinical reagent 3,5,3'5'-tetramethylbenzidine by prostaglandin synthase. 680 42

Fibronectin and procollagen types I and III are constituents of the extracellular matrix of human fibroblasts. Ultrastructural immunocytochemistry using the peroxidase anti-peroxidase method showed fibronectin and procollagen antibodies reacting in continuous fashion on 10 nm diameter extracellular fibrils on human fibroblasts. Intracellular localization showed an intense accumulation of procollagen within cells cultured under routine conditions. This accumulation appeared almost as if there were a blockade in secretion of procollagen under routine culture conditions. Cells treated with ascorbic acid do not have the dense intracellular accumulation of procollagens seen with the apparent blockade of secretion in cells cultured under routine conditions. Ascorbate treated cells also have a more pronounced extracellular accumulation of matrix fibronectin and procollagen constituents. At the electromicroscopic level a new 40 nm diameter fibril is formed after ascorbic acid treatment of human fibroblasts. Antibody to fibronectin and procollagen I and III are seen binding to the 40 nm diameter fibrils in a periodic or stuttered appearance. The fibronectin and procollagen antibodies react with a 70 nm axial repeat along these 40 nm fibrils formed after ascorbate treatment. These studies suggest that under routine culture conditions "precursor" fibrils of fibronectin and procollagen are formed. Ascorbic acid treatment leads to enhanced matrix formation. Ultrastructural studies clearly show antibodies to fibronectin bind to fibronectin on native collagen fibrils formed by human fibroblasts cultured with ascrobic acid. Lastly there is an asymmetric or 70 nm axial periodic distribution of fibronectin along these definitive or mature collagen fibrils formed after ascorbic acid treatment.
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PMID:Ascorbate-induced fibroblast cell matrix: reaction of antibodies to procollagen I and III and fibronectin in an axial periodic fashion. 700 7

The glutathione peroxidase-glutathione reductase system, an alternative pathway for metabolic utilization of H2O2 [Chance, Sies & Boveris (1979) Physiol. Rev. 59, 527-605], was investigated in Trypanosoma cruzi, an organism lacking catalase and deficient in peroxidase [Boveris & Stoppani (1977) Experientia 33, 1306-1308]. The presence of glutathione (4.9 +/- 0.7 nmol of reduced glutathione/10(8) cells) and NADPH-dependent glutathione reductase (5.3 +/- 0.4 munit/10(8) cells) was demonstrated in the cytosolic fraction of the parasite, but with H2O2 as substrate glutathione peroxidase activity could not be demonstrated in the same extracts. With t-butyl hydroperoxide or cumene hydroperoxide as substrate, a very low NADPH-dependent glutathione peroxidase activity was detected (equivalent to 0.3-0.5 munit of peroxidase/10(8) cells, or about 10% of glutathione reductase activity). Blank reactions of the glutathione peroxidase assay (non-enzymic oxidation of glutathione by hydroperoxides and enzymic oxidation of NADPH) hampered accurate measurement of peroxidase activity. The presence of superoxide dismutase and ascorbate peroxidase activity in, as well as the absence of catalase from, epimastigote extracts was confirmed. Ascorbate peroxidase activity was cyanide-sensitive and heat-labile, but no activity could be demonstrated with diaminobenzidine, pyrogallol or guaiacol as electron donor. The summarized results support the view that T. cruzi epimastigotes lack an adequate enzyme defence against H2O2 and H2O2-related free radicals.
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PMID:Deficient metabolic utilization of hydrogen peroxide in Trypanosoma cruzi. 700 79

Ascorbic acid hampers some test systems based on use of peroxidase (EC 1.11.1.7) and redox indicators, by producing a lag time in color development. With reversible indicators, no color development occurs during the ascorbic acid lag time. With oxidatively coupled indicator systems, such as 3-methyl-2-benzothiazolinone hydrazone (MBTH) and a suitable coupler such as chromotropic acid (CTA; 4,5-dihydroxynaphthalene-2,7-disulfonic acid), ascorbic acid diminishes the rate of color development, but does not abolish it. The effect of ascorbic acid strongly depends on the reaction pH as well as the nature of the coupler used. The ascorbate-elicited reduction (or lag) in color development was inversely proportional to the concentrations of MBTH and virtually unaffected by changes in CTA coupler concentration. The rate of color development following the lag was directly proportional to the concentration of MBTH but unaffected by the CTA. These observations suggest that peroxidase with H2O2 catalyzes the oxidation and activation of MBTH to an oxidized species (MBTHox). This species is reduced by ascorbic acid and at the same time couples oxidatively with CTA. Thus, the activity during the ascorbate-induced lag time reflects this competition of ascorbic acid and coupler for MBTHox. This study of peroxidase/ascorbate lag time with the redox coupled indicator system has led to the selection of fast couplers that are highly resistant to interference by ascorbic acid. Suitable resistant couplers (e.g., chromotropic acid, Chicago acid, and H acid) appear to be aromatic ring systems with highly activating substituents and directing toward electrophilic aromatic substitution at the ortho and para positions.
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PMID:Interference by ascorbic acid in test systems involving peroxidase. II. Redox-coupled indicator systems. 707 25

Subcellular fractions of pregnant rabbit ovary at day six of gestation catalysed the formation of progesterone from pregnenolone (3 beta-hydroxy-5-pregnen-20-one). The microsomal fraction was found to have maximum activity. The enzyme needed hydrogen peroxide for its activity. In vitro studies using horseradish peroxidase also showed similar conversion and this was stimulated 200% in the presence of ascorbic acid. Ascorbate thus appears to perform a catalytic role in this conversion. The importance of peroxidase in luteal steroidogenesis is indicated.
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PMID:Studies on peroxidase-catalyzed formation of progesterone. 718 86

Enzymatic removal of the cell wall induces vegetative Chlamydomonas reinhardtii cells to transcribe wall genes and synthesize new hydroxyproline-rich glycoproteins (HRGPs) related to the extensins found in higher plant cell walls. A cDNA expression library made from such induced cells was screened with antibodies to an oligopeptide containing the (SP)x repetitive domains found in Chlamydomonas wall proteins. One of the selected cDNAs encodes an (SP)x-rich polypeptide that also displays a repeated YGG motif. Ascorbate, a peroxidase inhibitor, and tyrosine derivatives were shown to inhibit insolubilization of both the vegetative and zygotic cell walls of Chlamydomonas, suggesting that oxidative cross-linking of tyrosines is occurring. Moreover, insolubilization of both walls was concomitant with a burst in H2O2 production and in extracellular peroxidase activity. Finally, both isodityrosine and dityrosine were found in hydrolysates of the insolubilized vegetative wall layer. We propose that the formation of tyrosine cross-links is essential to Chlamydomonas HRGP insolubilization.
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PMID:Isodityrosine cross-linking mediates insolubilization of cell walls in Chlamydomonas. 768 82

Human plasma glycerol was determined with a microdialysis electrode, containing the enzymes glycerol kinase and glycerol phosphate oxidase held stationary within the electrode. A microdialysis electrode is essentially a conventional microdialysis probe, with a platinum working electrode inserted into the tip of the dialysis fiber and reference and counter electrodes contained in the upper compartment. The linear range of response to glycerol was directly dependent on the concentration of ATP. At 4 mM ATP, the linear range was 0.5-500 microM. A fast response time of 20 s was obtained. Two types of interferences were observed when plasma glycerol was measured: direct oxidation of interferents at the electrode and attenuation of response to glycerol by reaction with hydrogen peroxide and/or poisoning of the platinum electrode. Ascorbate, urate, and acetaminophen were removed from plasma samples by a pretreatment step involving peroxidase and catalase. Any remaining interferent current was reduced by electropolymerizing o-phenylenediamine onto the platinum electrode. Adsorption of plasma proteins on the dialysis fiber was minimal and was not reduced by the preadsorption of human serum albumin. Very good correlation was obtained between the electrode and the standard spectrophotometric technique for the variation in glycerol concentration with time.
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PMID:Measurement in vitro of human plasma glycerol with a hydrogen peroxide detecting microdialysis enzyme electrode. 784 32


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