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)

The reaction products of peroxidase, a hydrogen donor and hydrogen peroxide decreased the amount of lysine recovered from proteins after acid hydrolysis. Oxidation of peroxidase treated proteins with performic acid prior to hydrolysis formed alpha-amino adipic acid indicating that the peroxidase or the quinones formed by peroxidase had oxidatively deaminated some lysyl residues of the protein to form lysyl aldehyde. Gel filtration and polyacrylamide gel electrophoresis revealed dimers, trimers and higher protein polymers that were not detected when peroxidase was omitted. Since some of the protein polymers were not dissociated by gel electrophoresis in the presence of dodecyl sulfate, urea and mercaptoethanol, it suggests that the free radicals or quinones formed by peroxidase had interacted with or cross-linked protein molecules by the formation of covalent bonds. Oxidative enzymes like peroxidase and polyphenol oxidase may lower the nutritive value of proteins by the oxidative deamination of lysine, reaction with cysteine and methionine and by cross-linking protein molecules to reduce their susceptibility to enzymatic hydrolysis.
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PMID:Cross-linking of protein by peroxidase. 2 Jul 49

Glutathione and cysteine bind to the heme of lactoperoxidase, thereby causing a red shift of the Soret band which is reversed upon addition of iodide or guaiacol, two substrates for lactoperoxidase. The rate of formation of the enzyme-thiol complex is enhanced by diiodotyrosine. Binding of diiodotyrosine to lactoperoxidase does not cause a shift of the Soret band which indicates binding to the protein of the enzyme. At neutral pH and low ionic strength, lactoperoxidase is adsorbed on insolubilized diiodotyrosine (diiodotyrosine-agarose). It can be eluted at slightly increased ionic strength which shows that the binding is weak. In the presence of 5 X 10(-4) M glutathione, however, the binding of the enzyme to diiodotyrosine-agarose becomes much stronger so that a high salt concentration is required for elution. Lactoperoxidase is also adsorbed on insolubilized thiols (thiol-agarose). The presence of diiodotyrosine is not required for strong binding. A simple method for the preparation of lactoperoxidase from milk by affinity chromatography is based on the interactions of the enzyme with the two ligands, thiols and diiodotyrosine.
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PMID:Interaction of lactoperoxidase with thiols and diiodotyrosine. 3 12

In the presence of MnCl2 and a thiol (glutathione, cysteine, 2-nitro-5-thiobenzoic acid) horse radish peroxidase oxidizes p-hydroquinone to p-benzoquinone which in turn immediately adds the thiol present yielding 2-S-substituted p-hydroquinone.
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PMID:Aerobic oxidation of p-hydroquinone by horse radish peroxidase in the presence of a thiol and MnCl2. 14 26

The concentrations of lactoperoxidase (LP) and thiocyanate (SCN-) in the mammary secretions of 4 dairy cows in the early dry period were similar to or higher than concentrations in the milk before drying off. The concentrations of free cystine progressively increased in the secretions beginning 3 to 5 days after the last milking; the mean concentrations were 0.66 mumoles/L before drying off and 6.66 mumoles/L after drying off. The mean concentrations of free cysteine were 0.28 mumoles/L before drying off and 1.4 mumoles/L after drying off. The secretions, when diluted in steamed milk, showed greater stimulation of Streptococcus agalactiae growth as the drying-off period progressed. This increase in stimulatory activity was attributed primarily to the increased concentrations of cystine because cystine counteracts the LP/SCN-/hydrogen peroxide inhibitory system for S agalactiae. This effect on the LP system may account for any increase in susceptibility to S agalactiae under infection during the dry period. In 3 other cows, the mammary secretions on the day of calving had lower mean concentrations of LP, SCN-, and free cystine and cysteine than those obtained 4 to 5 days before, and 7 to 8 days after calving.
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PMID:Lactoperoxidase, thiocyanate, and free cystine in bovine mammary secretions in early dry period and at the start of lactation and their effect on Streptococcus agalactiae growth. 38 Apr 19

The lactoperoxidase (LPO) activity in guinea-pig milk and saliva has been investigated in sows suckling normal young, and young orally infected with Escherichia coli. There was a 5-fold increase in activity in milk during the 3--4 weeks of lactation; infection of the young did not alter this. There was no comparable increase in lactoperoxidase activity of saliva during this same period, either in the infected or non-infected group. The antibacterial activity of milk from sows suckling normal young increased with the lactoperoxidase, and this bactericidal activity could be reversed by LPO inhibitors such as penicillamine and cysteine but not by addition of sufficient iron to saturate the lactoferrin. In milk from sows suckling infected young, bacteriostatic activity occurring in samples from about 14 days after infection needed iron or both iron and penicillamine (or cysteine) for reversal, indicating that both the antibody-lactoferrin system and the LPO system may be involved in the infected state.
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PMID:Lactoperoxidase activity in guinea-pig milk and saliva: correlation in milk of lactoperoxidase with bactericidal activity against Escherichia coli. 38 28

Cytochrome b-562.5 (Ulva pertusa) was extracted from a green alga, U. pertusa, by homogenization of the thalli in phosphate buffer solution. Purification was carried out by acrinol treatment, ammonium sulfate fractionation, DEAE-cellulose and DEAE-Sephadex column chromatographies, and Sephadex gel filtration. Cytochrome b-562.5 has absorption maxima at 562.5 (alpha), 530.5 (beta), 429 (gamma), and 326 nm (delta) in the reduced form and at 537, 415 (gamma), and 275 nm in the oxidized form. The alpha-band of the reduced form is asymmetric with a shoulder at 560 nm, at liquid nitrogen temperature this band splits into two distinct peaks at 562 and 556.5 nm. The absorption maxima of the pyridine ferrohemochrome appear at 556 (alpha), 523 (beta), and 418 nm (gamma). The cytochrome does not combine with carbon monoxide or cyanide. The preparation of the cytochrome shows little peroxidase activity. The cytochrome is oxidized by ferricyanide and reduced by cysteine, ascorbate, and hydrosulfite. Autoxidation of the cytochrome was found to be very slow. The midpoint potential (Em) of the cytochrome was determined by equilibration with the ferro- and ferri-EDTA system to be +0.20 V at pH7.0. The molecular weight of the cytochrome was estimated by Sephadex gel filtration to be 23x10(3).
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PMID:Purification and properties of cytochrome b-562.5 from Ulva pertusa. 42 58

Peptostreptococcus anaerobius VPI 4330-1 was exposed to atmospheric oxygen in a dilution bland (0.2% gelatin, salts, resazurin) solution. The organisms were rapidly killed when the solution contained cysteine. The organisms were effectively protected by catalase and horseradish peroxidase as well as by the metal ion-chelating agents 8-hydroxyquinoline and 2,2'-bipyridine. Superoxide dismutase increased the rate of killing of the organisms, whereas singlet oxygen quenchers and scavengers of hydroxyl free radicals did not protect the organisms from the toxic effect of cysteine. Hydrogen peroxide was formed when cysteine was exposed to oxygen in the dilution blank solution, and the reaction was inhibited by metal ion-chelating agents. The organisms were rapidly killed by 20 microM hydrogen peroxide in anaerobic dilution blank solution. The toxic effect of hydrogen peroxide in anaerobic dilution blank solution. The toxic effect of hydrogen peroxide was completely abolished by catalase and metal ion-chelating agents. These results indicated that hydrogen peroxide was formed in the dilution blank solution in a metal ion-catalyzed autoxidation of cysteine and that hydrogen peroxide was toxic to P. anaerobius VPI 4330-1 in a reaction also catalyzed by metal ions.
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PMID:Bactericidal effect of cysteine exposed to atmospheric oxygen. 45 19

Human parotid and submandibular glands were studied using histological techniques. Proteins rich in arginine, tyrosine, cystine-cysteine and tryptophan were present within secretory granules of seromucous acini and ducts of both glands. Acid phosphatase, ali-esterase, peroxidase and 3-beta-steroid-dehydrogenase were also demonstrated in the two glands.
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PMID:[Histochemical studies of the parotid and submandibular glands of humans]. 54 71

Protoporphyrin-sensitized photooxidation in human red blood cell membranes leads to severe deterioration of membrane structure and function. The membrane damage is caused by direct oxidation of amino acid residues, with subsequent cross-linking of membrane proteins. The chemical nature of these cross-links was studied in model systems, isolated spectrin and red cell ghosts. Cysteine and methionine are not involved in the cross-linking reaction. Further it could be shown that dityrosine formation, the crucial mechanism in oxidative cross-linking of proteins by peroxidase-H2O2 treatment, plays no role in photodynamic cross-linking. Experimental evidence indicated that a secondary reaction between free amino groups and a photooxidation product of histidine, tyrosine or tryptophan is involved in photodynamic cross-linking. This was deduced from the reaction observed between compounds containing a free amino group and photooxidation products of these amino acids, both in model systems, isolated spectrin and erythrocyte ghosts. In accordance, succinylation of free amino groups of membrane proteins or addition of compounds with free amino groups protected against cross-linking. Quantitative data and consideration of the reaction mechanisms of photodynamic oxidation of amino acids make it highly probable that an oxidation product of histidine rather than of tyrosine or tryptophan is involved in the cross-linking reaction, via a nucleophilic addition by free amino groups.
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PMID:Photodynamic effects of protoporphyrin on human erythrocytes. Nature of the cross-linking of membrane proteins. 67 40

A single reagent, containing cholesterol oxidase, cholesterol esterase, peroxidase, 4-hydroxybenzoate, and 4-aminophenazone, is used in determining serum cholesterol. Analysis time is 15 min, and the standard curve is linear to 6.0 g/liter. Analytical recovery of cholesterol was 100.1 +/- 0.4%. Within-run precision (CV) was less than or equal to 1.4 1.4%, between-run less than or equal to 4.8%. Comparison with results by a Liebermann Burchard method [Clin. Chim. Acta 5, 637 (1960)] gave a linear regression of y = 1.08x--0.05, with a correlation coefficient (r) of 0.985. Comparison with the Roeschlau enzymic method [J. Clin. Chem. Clin. Biochem, 12, 226 (1974)] gave y = 1.02x + 0.01 (r = 0.958). Comparison with the enzymic method of Allain et al. [Clin. Chem. 20, 470 (1974)] gave y = 1.01x--0.00 (r = 0.995). The following substances do not interfere up to the indicated concentrations (mg/liter): hemoglobin (5000), bilirubin (100), reduced glutathione (150), l-cysteine (400), urea (3000), creatinine (200), uric acid (200), d-glucose (10000), L-ascorbic acid (50), acetylsalicylic acid (500), L-DOPA (10), ergothioneine (1000), 2,5-dihydroxybenzoic acid (20), and 3,4-dihydroxybenzoic acid (10). Stored in an amber-colored bottle, the working reagent is stable for three months at 2--8 degrees C and for three weeks at 25 degrees C.
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PMID:The 4-hydroxybenzoate/4-aminophenazone chromogenic system used in the enzymic determination of serum cholesterol. 71 64


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