Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PEROXIDASES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,441 records · Page 80Linked to original sources
PubMed1980

Covalent attachment of horseradish peroxidase to the outer surface of liposomes.

We describe a method by which horseradish peroxidase may be attached covalently to the surface of liposomes under conditions which permit minimal non-covalent association of the enzyme with the lipids. The coupling method adopted does not allow the formation of homopolymers of liposomes or peroxidase. For phosphatidylelthanolamine/phosphatidylcholine and stearylamine/phosphatidylcholine and vesicles, minimal disruption of vesicular structure is observed, whilst for phosphatidylserine vesicles, the lipid-protein complex appears to form structures much smaller than 25 nm in diameter. Stearylamine/phosphatidylcholine vesicles have been shown to retain entrapped inulin, and activity measurements for the peroxidase suggest that it is located exclusively on the external surface of the liposome membrane. Peroxidase can be localized histochemically which has permitted the morpholo gical study of the coated liposomes and their interactions with cells.

Animals↗
PubMed1988

Comparative investigations on the uptake of phallotoxins, bile acids, bovine lactoperoxidase and horseradish peroxidase into rat hepatocytes in suspension and in cell cultures.

Two alternative uptake mechanisms for phallotoxins by liver cells are debated: carrier-mediated uptake and receptor-mediated endocytosis. We have compared the properties of hepatocellular uptake of the phallotoxins, phalloidin and demethylphalloin, with the uptake of cholate as a substrate for carrier-mediated uptake and compared with iodinated bovine lactoperoxidase or iodinated horseradish peroxidase, as the latter are known to be taken up by vesicular endocytosis. Uptake of phallotoxins and [14C]cholate uptake into isolated hepatocytes is independent of extracellular calcium but inhibited by A23187 or by monensin. Uptake of bovine lactoperoxidase strictly depends on external Ca2+, was insensitive to A23197 and was not inhibited by monensin. No mutual uptake inhibition between phalloidin or cholate and peroxidases was seen, indicating independent permeation pathways in hepatocytes. However, high concentrations of cytochalasin B inhibited the uptake of either phalloidin, cholate or bovine lactoperoxidase. Horseradish peroxidase uptake, which was taken as an indicator for fluid pinocytosis, was low in isolated hepatocytes and could not account for the amount of phalloidin or cholate taken up. In cultured rat hepatocytes, uptake of phallotoxins decreased within 1 day to 10% of the uptake seen in freshly isolated hepatocytes. The results indicate different mechanisms for hepatocellular phallotoxin/bile-acid uptake and peroxidase internalization. As monolayer cultures of hepatocytes rapidly lost the carrier-mediated uptake of phallotoxins and bile acids, freshly isolated hepatocytes might be a more suitable experimental model than cultured cells for kinetic studies on this transport system.

Amanitins↗
PubMed1980

Oxidized forms of ovine erythrocyte glutathione peroxidase. Cyanide inhibition of a 4-glutathione:4-selenoenzyme.

[75Se]Glutathione peroxidase (glutathione:hydrogen-peroxide oxidoreductase, EC 1.11.1.9) containing 4 mol selenium per mol was isolated in 33% yield using 10% ethanol to stabilize the purified enzyme. When reduced with GSH and rapidly separated from GSH by gel filtration chromatography, GSH peroxidase was eluted in a labile oxidized (iodoacetate-insensitive) form which was stable at 4 degrees C but unstable at 25 degrees C (form A). When GSH-reduced enzyme was allowed to oxidize in the course of dialysis a more stable oxidized form was obtained (form C) which was rapidly inactivated by cyanide. Using [35S]GSH, form C was shown to contain tightly bound glutathione in approx. equimolar ratio with selenium. The cyanide sensitivity of GSH peroxidase is therefore correlated with the presence of a glutathione moiety in the enzyme. The isolation of GSH peroxidase containing bound glutathione suggests that intermediates containing glutathione bound to selenium may be formed during the catalytic cycle.

Animals↗
PubMed1980

Purification and immunohistochemical localization of rat liver glutathione peroxidase.

Glutathione peroxidase was purified from the rat liver to give a single protein band in polyacrylamide gel electrophoresis. Rabbits were immunized with this purified enzyme, and a highly specific anti-glutathione peroxidase antiserum was obtained. Using this antibody, an immunohistochemical technique (the indirect method of peroxidase-labeled antibody) was applied to study the localization of the enzyme in the liver cells. On immunohistochemical observation, glutathione peroxidase was localized exclusively in the cytoplasm of hepatocytes, and a stronger 'immuno-staining' was exhibited in the peripheries of the hepatic lobules than in the central zone.

Animals↗
PubMed1983

The role of porcine thyroid peroxidase and FAD-containing monooxygenase in the metabolism of 1-methyl-2-thioimidazole (methimazole).

The peroxidase and FAD-containing monooxygenase activities of porcine thyroid subcellular preparations were measured and it was observed that FAD-containing monooxygenase activity was considerably lower than that of peroxidase. The end product of 1-methyl-2[14C]thioimidazole oxidation catalysed by thyroid peroxidase was confirmed to be 1-methylimidazole by mass spectrometry. In the presence of thyroid peroxidase 1-methyl-2-thioimidazole would appear initially to be oxidised to bis(1-methylimidazole)-2,2'-disulphide. The extent of oxidation was dependent on the iodide concentration in the reaction mixture.

Animals↗
PubMed1983

Effect of butylated hydroxytoluene on glutathione S-transferase and glutathione peroxidase activities in rat liver.

When rats were fed a diet containing 0.4% (w/w) butylated hydroxytoluene (BHT), glutathione (GSH) S-transferase activity towards 1-chloro-2,4-dinitrobenzene (CDNB) increased approximately 3-fold in the liver. Immunotitration studies using the antibodies raised against rat liver GSH S-transferase B and GSH S-transferase A and C indicated that the increase in GSH S-transferase activity was probably due to de novo protein synthesis. Since some forms of rat liver GSH S-transferases express GSH peroxidase II activity, a concomitant increase in GSH peroxidase II was expected. However, GSH peroxidase II activity in the liver of BHT-treated rats remained unchanged. Gel filtration of supernatant fractions from livers of control and BHT-treated rats, followed by isoelectric focusing, indicated that BHT induced the activity of hepatic GSH S-transferases, without any apparent effect on GSH peroxidase II activity.

Animals↗
PubMed1988

Inactivation of peroxidases of rat bone marrow by repeated administration of propylthiouracil is accompanied by a change in the heme structure.

Myeloperoxidase and eosinophil peroxidase were isolated from the bone marrow cells of rats treated with or without propylthiouracil (PTU) which caused bone marrow depression. PTU treatment decreased the activity of myeloperoxidase but not of eosinophil peroxidase using guaiacol as the electron donor. However, when KI,N-N'-dimethyl-p-phenylenediamine and pyrogallol were used as the electron donor, the activity of only eosinophil peroxidase was inhibited by PTU treatment. EPR spectra indicated that the structure of myeloperoxidase surrounding the heme iron changed from a rhombic form into an axial one by the repeated administration of PTU. Therefore, the inactivation of peroxidases by PTU treatment was accompanied by an alteration of their structures surrounding the heme.

Animals↗
PubMed1982

Glutathione peroxidase in human cerebrospinal fluid.

Glutathione peroxidase activity was investigated in human cerebrospinal fluid. CSF was obtained from 23 male adult patients with dementia, cerebrovascular disease and multiple sclerosis. The mean glutathione peroxidase activity in the CSF was 6.2 nmol NADPH oxidized min-1 . mg-1 protein +/- 0.6 S.E.M. No differences in the activities were observed in these neurological diseases suggesting that this value may reflect normal glutathione peroxidase activity in human CSF. The age or the protein concentration in CSF did not correlate significantly with glutathione peroxidase activity in CSF.

Adult↗
PubMed1982

Secretion-related accumulation of horseradish peroxidase in magnocellular cell bodies of the rat supraoptic nucleus.

The uptake and intracellular distribution of intravenously injected horseradish peroxidase were studied at various time intervals to trace the fate of endocytotic vacuoles formed at axon terminals in the neurohypophyses of normal and water deprived rats. Up to 4 h after tracer administration, enzymatic reaction product was limited to the cytoplasm of the neurohypophysial axons sequestered mainly in large vacuoles and cup-shaped organelles; with increasing time, it was also present in multivesicular bodies. Four hours after tracer injection, profiles labeled with peroxidase also appeared within neurosecretory perikarya in the supraoptic nucleus of the hypothalamus. Perikaryal organelles containing reaction product included vacuoles of various size, tubular profiles, multivesicular bodies and residual bodies. Morphometric analysis indicated that the accumulation of peroxidase-labeled profiles, both in the neurohypophysial axons and in the supraoptic perikarya, is closely related to secretion, for there was a highly significant augmentation in the relative volume occupied by such organelles in preparations from dehydrated animals, at 4 and 8 h after tracer injection, as compared to their corresponding controls. The analysis demonstrates moreover, that with increasing time, the mean volume density of peroxidase-labeled organelles in the supraoptic perikarya increased, whilst that in the neurohypophysial axons diminished. In the perikarya, reaction product progressively accumulated in the lysosomal multivesicular and residual bodies. These observations suggest that material internalized by compensatory endocytosis at the neurosecretory terminals after the release of hormone by exocytosis is subsequently removed by retrograde axonal transport to their perikarya in the hypothalamus where it gradually becomes sequestered in lysosomes. Whether all the material retrieved at the terminals, especially the membrane, is ultimately degraded remains to be determined.

Animals↗
PubMed1978

Improved assay procedures for thyroid peroxidase; application to normal and adenomatous human thyroid tissue.

We have developed assays for thyroid peroxidase in crude thyroid tissue preparations, in which a linear relationship between activity and amount of tissue could be demonstrated. Linear assays were developed based on the following peroxidase catalyzed reactions in the presence of H2O2:(1) oxidation of I- to I(-3), (2) oxidation of guaiacol, and (3) iodination of human goiter thyroglobulin. To attain satisfactory linearity we found it necessary to solubilize the enzyme beforehand. This was accomplished by a brief treatment of the particulate fraction with trypsin and deoxycholate, followed by centrifugation at 40 000 X g and dialysis. Not only did this treatment facilitate the development of linear assays, but it also resulted in a substantial increase in enzyme activity compared with that in the untreated particulate fraction. The use of a Polytron homogenizer for the initial disruption of the tissue also proved helpful in developing these assay procedures. The three different assays were used to measure peroxidase activities in human thyroid adenomas and in normal tissue derived from adenomatous glands. T he adenomas generally displayed a higher level of peroxidase activity than normal tissue. The greatest difference was observed with the iodination assay and the smallest difference with the guaiacol assay.

Adenoma↗
PubMed1983

Peroxidase secretion from rat lacrimal gland cells in vitro: II. The role of calcium in stimulus-secretion coupling.

The role of calcium in stimulus-secretion coupling in rat lacrimocytes was investigated. Monolayers of lacrimocytes released peroxidase into the incubation medium upon stimulation with calcium ionophore A 23187, L-norepinephrine, L-phenylephrine and tyramine. Our lacrimocyte preparation can be considered free of endogenous catecholamines, because lacrimocytes derived both from normal and from reserpinized rats responded to tyramine with respect to peroxidase secretion. Phenoxybenzamine, cocaine, verapamil and sodiumorthovanadate failed to inhibit the L-phenylephrine-evoked peroxidase secretion. The stimulatory effects of A 23187, L-norepinephrine and L-phenylephrine required extracellular Ca2+ and could be blocked by phentolamine. The action of tyramine was insensitive to all these measures. It is suggested that the stimulus-secretion of peroxidase from lacrimocytes may consist of a Ca2+-dependent phase for stimulants as A 23187, L-norepinephrine and L-phenylephrine and a Ca2+-independent phase for the non-specific tyramine action.

Animals↗
PubMed1983

Steady-state kinetics of thyroid peroxidase. Evidence for a high degree rate equation using the F statistic.

The initial-rate kinetics of bovine thyroid peroxidase are reported using 325 sets of concentrations of hydrogen peroxide and guaiacol. Extended ranges of concentrations are used and the v(S) profiles are fitted by rational functions of degree 2:2, 3:3 and +:4 by interactive non-linear regression analysis. Estimates of initial slopes in v(S) plots obtained by this regression are then replotted against the fixed substrate concentration and this confirms the need for a high-degree rate equation. Values of the F statistic indicate that the rate equation is 3:3 in guaiacol and 4:4 in hydrogen peroxide. It is concluded that the kinetics of peroxidase from bovine thyroid, like horse radish and human cervical mucus peroxidase and lactoperoxidase can be accommodated by the greater cyclic mechanism and that this is the minimal kinetic scheme for peroxidase In general.

Animals↗
PubMed1983

Adaptation of the Ngo-Lenhoff peroxidase assay for solid phase ELISA.

A modification of the Ngo-Lenhoff peroxidase assay has been developed. By this method, peroxidase is detectable at 5 fmoles of peroxidase per ml. The assay is easy to perform and the reagents are inexpensive. We have modified the buffer by the addition of citric acid and sodium azide to reduce background color development and to inhibit the activity of catalase, respectively. Production of the indamine dye by the peroxidase reaction is rapid but it may be stopped by lowering the pH to 3.0. The pH change of 7.0 to 3.0 is accompanied by a color change from purple-blue to blue and a shift in the maximum absorbance from 590 nm to 595 nm. The sensitivity of the assay was unaffected by these modifications.

Binding, Competitive↗
PubMed1984

Depression of estrogen-induced uterine peroxidase in alloxan-diabetic rats.

The influence of alloxan diabetes on reproductive function and the estradiol-stimulated increase in uterine peroxidase was investigated. Alloxan monohydrate in a dose of 75 mg/kg body weight effectively produced permanent diabetes. In adult rats, 20 days of diabetes resulted in cessation of the estrous cycle and a significant reduction in the gain of body weight, the weights of anterior pituitary gland, ovary, uterus, the level of serum progesterone and the activity of the estradiol-stimulated uterine peroxidase (P less than 0.05). After 10 days of insulin treatment, the ovarian weight, the estrous cycle and the level of ovarian hormones were restored to normal whereas the uterine weight and the estradiol-stimulated uterine peroxidase activity were only partially recovered. Persistent depression of the uterine response in the insulin-treated diabetic rats to both endogenous and exogenous ovarian hormone stimulation suggests that the uterus was directly affected by diabetes. The direct effect of diabetes upon the uterus was further demonstrated in the ovariectomized immature rat in which diabetes depressed the stimulatory action of estradiol on both uterine weight and uterine peroxidase activity.

Animals↗
PubMed1987

Amino acid sequences of the two heme c-binding sites of Pseudomonas cytochrome-c peroxidase.

The amino acid sequences of the two heme c-containing tryptic peptides of Pseudomonas cytochrome-c peroxidase have been determined. The tryptic peptides were isolated from two cyanogen bromide fragments of the protein. Both heme-binding sites have the Cys-X-Y-Cys-His structure characteristic of c-type cytochromes. The sequences of the two peptides show distinct homology with each other, suggesting the occurrence of gene doubling during evolution of the protein molecule. The function of the heme c moieties in the catalytic cycle of the enzyme is discussed on the basis of their homology with the proximal histidine region of peroxidase (horseradish peroxidase and yeast cytochrome-c peroxidase) and cytochromes (horse cytochrome c and Pseudomonas cytochrome c-551).

Amino Acid Sequence↗
PubMed1991

Nucleotide sequences of two genomic DNAs encoding peroxidase of Arabidopsis thaliana.

The peroxidase (EC 1.11.1.7)-encoding gene of Arabidopsis thaliana was screened from a genomic library using a cDNA encoding a neutral isozyme of horseradish, Armoracia rusticana, peroxidase (HRP) as a probe, and two positive clones were isolated. From the comparison with the sequences of the HRP-encoding genes, we concluded that two clones contained peroxidase-encoding genes, and they were named prxCa and prxEa. Both genes consisted of four exons and three introns; the introns had consensus nucleotides, GT and AG, at the 5' and 3' ends, respectively. The lengths of each putative exon of the prxEa gene were the same as those of the HRP-basic-isozyme-encoding gene, prxC3, and coded for 349 amino acids (aa) with a sequence homology of 89% to that encoded by prxC3. The prxCa gene was very close to the HRP-neutral-isozyme-encoding gene, prxC1b, and coded for 354 aa with 91% homology to that encoded by prxC1b. The aa sequence homology was 64% between the two peroxidases encoded by prxCa and prxEa.

Amino Acid Sequence↗
PubMed2004

Construction of a subtractive library from hexavalent chromium treated winter flounder (Pseudopleuronectes americanus) reveals alterations in non-selenium glutathione peroxidases.

Chromium is released during several industrial processes and has accumulated in some estuarine areas. Its effects on mammals have been widely studied, but relatively little information is available on its effects on fish. Gene expression changes are useful biomarkers that can provide information about toxicant exposure and effects, as well as the health of an organism and its ability to adapt to its surroundings. Therefore, we investigated the effects of Cr(VI) on gene expression in the sediment dwelling fish, winter flounder (Pseudopleuronectes americanus). Winter flounder ranging from 300 to 360 g were injected i.p. with Cr(VI) as chromium oxide at 25 microg/kg chromium in 0.15N KCl. Twenty-four hours following injections, winter flounder were euthanized with MS-222 and the livers were excised. Half of the livers were used to make cytosol and the other half were used to isolate mRNA for subtractive hybridization. Subtractive clones obtained were spotted onto nylon filters, which revealed several genes with potentially altered expression due to Cr(VI), including an alpha class GST, 1-Cys peroxiredoxin (a non-selenium glutathione peroxidase), a P-450 2X subfamily member, two elongation factors (EF-1 gamma and EF-2), and complement component C3. Semi-quantitative RT-PCR was performed and confirmed that Cr(VI) down-regulated complement component C3, an EST, and two potential glutathione peroxidases, GSTA3 and 1-Cys peroxiredoxin. In addition, cytosolic GSH peroxidase activity was reduced, and silver stained SDS-PAGE gels from glutathione-affinity purified cytosol demonstrated that a 27.1 kDa GSH-binding protein was down-regulated greater than 50%. Taken together, Cr(VI) significantly altered the expression of several genes including two potential glutathione peroxidases in winter flounder.

Amino Acid Sequence↗