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At least 1,207 records · Page 67Linked to original sources
PubMed1992

The isolation and partial characterization of catalase and a peroxidase active fraction from human white adipose tissue.

1. A procedure is described for the purification of catalase and a peroxidase active fraction from human white adipose tissue. 2. Gel electrophoresis on SDS-PAGE revealed relative molecular masses of 202,900 and 208,600 for the active catalase and peroxidase molecules respectively (nonreducing conditions), as compared to 56,800 and 49,800 for the monomers under reducing conditions, thus indicating the likelihood of tetramers in the intact state. 3. The two purified enzymes differ with regard to pH optima (5-9 for catalase and 3 for peroxidase), temperature stability (up to 50 degrees C for catalase and 70 degrees C for peroxidase) and Km values towards H2O2 (38.9 mM for catalase and 7.69 mM for peroxidase, which was also active in oxidizing a number of o-dihydricphenols as second substrates). 4. The catalase enzyme showed uncompetitive inhibition by the irreversible inhibitor 3-amino-1,2,4-triazole (AT), Ki = 5.4 mM.

Adipose Tissue↗
PubMed1988

Efficient inhibition of endogenous peroxidase without antigen denaturation in immunohistochemistry.

The immunoperoxidase technique is commonly used for the antigenic characterization of cells and tissues. However, the occurrence of endogenous peroxidase-positive cells frequently complicates such evaluations. In some instances it is impossible to distinguish between these cells and antibody-stained cells. Methods so far described for inhibiting the endogenous peroxidase, are not always satisfactory - either the endogenous peroxidase is not satisfactorily blocked, or the cellular antigens lose their reactivity. A new two-step method is described which involves transient inhibition of endogenous peroxidase by sodium azide and hydrogen peroxide and a final blocking of this enzyme by lowering the pH to 2.3, while antigens remain undamaged. This method may be of value in immunohistochemical studies of various tissues, especially inflammatory tissues which contain many endogenous peroxidase-positive cells.

Animals↗
PubMed1986

An ultrastructural study of the segmental uptake of horseradish peroxidase in the endplate region of denervated skeletal muscle fibres.

The segmental uptake of horseradish peroxidase (HRP) in the endplate region of denervated skeletal muscle fibres has been studied ultrastructurally using a method for selecting single muscle fibres with high segmental peroxidase staining from denervated mouse tibialis anterior muscle. Segments containing large peroxidase positive phagosomes could already be seen 10-15 min after i.v. injection of HRP. Such segments were still present 24 h after HRP injection. The localization of phagosomes, deep in the fibres rather than immediately under the sarcolemma, suggests that the uptake occurs from t-tubuli. Vivid proliferation of t-tubuli, consisting of vesiculation, enlargement and encircling of cytoplasmic components, was also observed. The HRP accumulates in phagosomes of varying size and shape. Similar membrane-limited bodies without or with very weak peroxidase staining were also observed. The peroxidase-positive phagosomes participate in autophagic processes as suggested by their content of undegraded cellular material. Golgi profiles, which occurred deep in the muscle fibres, and enlarged components of the sarcoplasmic reticulum were frequently encountered in the segments. Myofibrillar degeneration occurs in the segments and progresses with time after denervation. The described segments may be related to the increased membrane turnover in denervated muscle fibres and/or they may be related to processes aimed at establishing new synaptic contacts.

Animals↗
PubMed1994

Immunohistochemical localization of glutathione peroxidase in infarcted human brain.

This is the first report which demonstrates the presence of glutathione peroxidase in the autopsied brain of 5 patients without cerebral infarction and 21 patients with cerebral infarction by the indirect enzyme-labeled antibody technique with monoclonal antibody to human glutathione peroxidase. In 2 out of 5 patients without cerebral infarction, a weak reaction for glutathione peroxidase was demonstrated both in neurons and glia. In 6 patients who had died within 5 days after stroke, no staining was observed in infarcted brain tissue except in macrophages. In all 15 patients who had died more than 6 days after stroke, however, a reaction for glutathione peroxidase was demonstrated in the cytoplasm of glial cells in the marginal area around the infarction, and there was a patchy reaction in the cytoplasm of macrophages in the core lesion. These results suggest that glutathione peroxidase in glial cells of the marginal area around the infarction may play a protective role against lipid peroxidation after cerebral infarction, or alternatively, may be involved in the healing process after ischemia.

Adult↗
PubMed1991

Characteristics of estrogen-induced peroxidase in mouse uterine luminal fluid.

Peroxidase activity in the uterine luminal fluid of mice treated with diethylstilbestrol was measured by the guaiacol assay and also by the formation of 3H2O from [2-3H]estradiol. In the radiometric assay, the generation of 3H2O and 3H-labeled water-soluble products was dependent on H2O2 (25 to 100 microM), with higher concentrations being inhibitory. Tyrosine or 2,4-dichlorophenol strongly enhanced the reaction catalyzed either by the luminal fluid peroxidase or the enzyme in the CaCl2 extract of the uterus, but decreased the formation of 3H2O from [2-3H]estradiol by lactoperoxidase in the presence of H2O2 (80 microM). NADPH, ascorbate, and cytochrome c inhibited both luminal fluid and uterine tissue peroxidase activity to the same extent, while superoxide dismutase showed a marginal activating effect. Lactoferrin, a major protein component of uterine luminal fluid, was shown not to contribute to its peroxidative activity, and such an effect by prostaglandin synthase was also ruled out. However, it was not possible to exclude eosinophil peroxidase, brought to the uterus after estrogen stimulation, as being the source of peroxidase activity in uterine luminal fluid.

Animals↗
PubMed1990

Multiple lignin peroxidases of Phanerochaete chrysosporium INA-12.

Nine proteins with lignin peroxidase activity were separated from cultures of Phanerochaete chrysosporium INA-12 in glycerol as carbon source and non-nitrogen limited. Four lignin peroxidase isozymes (4, 5, 8, 9) were purified and characterized. Although differences in kinetic parameters could be shown, antibody reaction showed homology between isozymes. However, thermal stability studied, peptide mapping results, and N-terminal sequence analyses established a higher degree of homology between isozymes 4/5 and 8/9 types. Protein characterization and kinetic data indicate that lignin peroxidase isozymes 4, 5, 8, and 9 differ from described isozymes in strain BKM. The higher specific activity of lignin peroxidase isozymes in cultures with glycerol than in nitrogen-starved cultures accounts for the higher lignin peroxidase activity obtained in these conditions.

Amino Acid Sequence↗
PubMed1990

Role of the glutathione-glutathione peroxidase cycle in the cytotoxicity of the anticancer quinones.

Recent studies have suggested that the selenoenzyme glutathione peroxidase, in the presence of reducing equivalents from the tripeptide glutathione, is responsible for detoxifying hydrogen peroxide and lipid hydroperoxides generated as a consequence of the cyclic reduction and oxidation of quinone-containing anticancer agents including doxorubicin, daunorubicin, mitomycin C, diaziquone, and menadione. Alterations in the intracellular levels of glutathione peroxidase or glutathione can significantly affect the activity of these drugs against human tumor cells and the expression of their normal tissue toxicity, especially with respect to the heart. Furthermore, augmentation of the glutathione peroxidase pathway appears to render certain human tumor cells relatively resistant to the anticancer quinones; therefore, the glutathione peroxidase system may, at least in part, modulate certain forms of acquired drug resistance in man. Thus, the glutathione peroxidase cycle appears to play a central role in maintaining intracellular peroxide homeostasis during quinone-induced oxidative stress.

Animals↗
PubMed1994

A fluorometric assay of peroxidase activity utilizing 2',7'-dichlorofluorescein with thiocyanate: application to the study of salivary secretion.

A sensitive assay for secretory peroxidase activity has been developed utilizing the fluorogenic substrate 2',7'-dichlorofluorescin in the presence of thiocyanate. The assay has been characterized using bovine lactoperoxidase and used to determine the peroxidase activities of salivas and extracts obtained from rat submandibular glands. Comparison of the 2',7'-dichlorofluorescin-thiocyanate assay and the commonly used 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) colorimetric assay indicates that the new assay is approx. 50-fold more sensitive. This has enabled measurement of peroxidase activities present in parasympathetic saliva samples which were beyond the detection limit of the colorimetric assay. Despite great differences in the peroxidase activities and protein concentrations of parasympathetic and sympathetic salivas and tissue extracts, the activities per unit protein were very similar. Unlike most other published methods, prior dialysis of samples to remove interference by endogenous thiocyanate is not required. The assay is therefore convenient and will be particularly useful for applications in which sample volume or peroxidase activity is low.

Animals↗
PubMed1994

A fluorometric assay of peroxidase activity utilizing 2',7'-dichlorofluorescein with thiocyanate: application to the study of salivary secretion.

A sensitive assay for secretory peroxidase activity has been developed utilizing the fluorogenic substrate 2',7'-dichlorofluorescein in the presence of thiocyanate. The assay has been characterized using bovine lactoperoxidase and used to determine the peroxidase activities of salivas and extracts obtained from rat submandibular glands. Comparison of the 2',7'-dichlorofluorescein-thiocyanate assay and the commonly used 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) colorimetric assay indicates that the new assay is approx. 50-fold more sensitive. This has enabled measurement of peroxidase activities present in parasympathetic saliva samples which were beyond the detection limit of the colorimetric assay. Despite great differences in the peroxidase activities and protein concentrations of parasympathetic and sympathetic salivas and tissue extracts, the activities per unit protein were very similar. Unlike most other published methods, prior dialysis of samples to remove interference by endogenous thiocyanate is not required. The assay is therefore convenient and will be particularly useful for applications in which sample volume or peroxidase activity is low.

Animals↗
PubMed1995

Hydrogen peroxide degradation and glutathione peroxidase activity in cultures of thyroid cells.

The degradation rate of H2O2, added to the incubation medium, and glutathione (GSH) peroxidase activity were measured in cultures of FRTL-5 cells and porcine thyroid cells. The H2O2 degradation rate increased proportionally to the H2O2 concentration and was in FRTL-5 cells, cultured with TSH, approximately 50 nmol/min and mg DNA at 0.01 mM H2O2 and approximately 3 x 10(4) nmol/min and mg DNA at 10 mM H2O2. The GSH peroxidase activity in the same cells was equivalent to an H2O2 degradation of approximately 400 nmol/min and mg DNA. The involvement of enzymes in H2O2 degradation was studied by inhibiting catalase with aminotriazole (ATZ) and reducing GSH peroxidase by omitting glucose in the incubation medium. At 0.1 mM H2O2, ATZ or glucose omission alone did not measurably reduce H2O2 degradation but did so when combined. At 10 mM H2O2 ATZ caused a clear inhibition whereas glucose omission had no additive effect. These observations indicate that GSH peroxidase was involved in H2O2 degradation only at low H2O2 concentrations. The GSH peroxidase activity decreased by reduction of the selenite supply and increased after replenishment. The recovery of the enzyme activity required the presence of TSH in FRTL-5 cells but not in porcine thyrocytes.

Amitrole↗
PubMed1980

Peroxidase activity in the rat Zymbal gland and its possible role in the metabolic activation of aminostilbenes in the target tissue.

Peroxidase (EC 1.11.1.7) activity is detected in the rat Zymbal gland, which is the target organ of trans-4-dimethylaminostilbene (trans-DAS) carcinogenicity. Measurements of peroxidase activity in ovariectomized rats show that the enzyme activity is lowered in the uterus and Zymbal gland by trans-DAS treatment and in the lungs by diethylstilboestrol (DES) treatment. In an in vitro system containing horseradish peroxidase (HRP), hydrogen peroxide and calf-thymus DNA, irreversible binding of the 3H-labelled trans-DAS metabolites 3-hydroxy-, 4'-hydroxy-, and N-hydroxy-4-acetylaminostilbene to DNA is observed. The peroxidase activity in the Zymbal gland together with the HRP-catalyzed oxidation of trans-DAS metabolites suggest a possible role for peroxidase in the organ-specific metabolic activation of trans-DAS.

Animals↗
PubMed1990

Nonsteroidal anti-inflammatory drugs inhibit gastric peroxidase activity.

The peroxidase activity of the mitochondrial fraction of rat gastric mucosa was inhibited with various nonsteroidal anti-inflammatory drugs (NSAIDs) in vitro. Indomethacin was found to be more effective than phenylbutazone (PB) or acetylsalicylic acid (ASA). Mouse gastric peroxidase was also very sensitive to indomethacin inhibition. Indomethacin has no significant effect on submaxillary gland peroxidase activity of either of the species studied. Purified rat gastric peroxidase activity was inhibited 75% with 0.15 mM indomethacin showing half-maximal inhibition at 0.04 mM. The inhibition could be withdrawn by increasing the concentration of iodide but not by H2O2. NSAIDs inhibit gastric peroxidase activity more effectively at acid pH (pH 5.2) than at neutral pH. Spectral studies showed a bathochromic shift of the Soret band of the enzyme with indomethacin indicating its interaction at or near the heme part of the enzyme.

Animals↗
PubMed1979

Peroxidases produced by the marine sponge Iotrochota birotulata.

1. Two peroxidases, differing in ionic character and substrate specificity, have been isolated from the tropical marine sponge Iotrochota birotulata. 2. Both peroxidases catalyze the oxidation of a number of substrates, and one peroxidase possesses a specificity similar to the terrestrial fungal enzyme chloroperoxidase. 3. Based on inhibition studies utilizing sodium azide, potassium cyanide and 8-hydroxyquinoline, it appears that the peroxidases from I. birotulata are haemoprotein complexes. 4. One peroxidase appears to possess subunit structure, and requires bound divalent metal cations for activity.

Animals↗
PubMed1987

Synaptic organization of the cat entopeduncular nucleus with special reference to the relationship between the afferents to entopedunculothalamic projection neurons: an electron microscope study by a combined degeneration and horseradish peroxidase tracing technique.

The synaptic organization of the feline entopeduncular nucleus was studied electron microscopically. After horseradish peroxidase injections into the ventral anterior and ventral lateral nuclear complex of the thalamus, normal axon terminals synapsing with entopedunculothalamic projection neurons were classified into four types on the basis of the size and shape of synaptic vesicles in them, and types of the postsynaptic membrane differentiation. Type I and type II axon terminals were characterized by symmetrical synaptic contacts, and large ovoid or small ovoid synaptic vesicles, respectively. Type II axon terminals were further classified into two subtypes as to their sizes: one was small (IIa), the other large (IIb). Type III and type IV axon terminals were characterized by asymmetrical synaptic contacts, and large ovoid or small ovoid synaptic vesicles, respectively. To determine the origin of each type of terminal, electrolytic lesions of the caudate nucleus or the subthalamic nuclear region were combined with horseradish peroxidase injections into the thalamus or the subthalamic nuclear region. After electrolytic lesions of the caudate nucleus, degeneration was seen in type I axon terminals contacting entopedunculothalamic projection neurons. Following electrolysis or horseradish peroxidase injection into the subthalamic nuclear region, type IIa and type IV axon terminals showed degenerations or horseradish peroxidase labelling. Such terminals also synapsed with entopedunculothalamic projection neurons. It was demonstrated that these projection neurons relay the striatal or subthalamic inputs directly to the thalamus. After horseradish peroxidase injection into the thalamus, many labelled type II axon terminals were observed to synapse with entopedunculothalamic projection neurons. Type III axon terminals were left unchanged throughout these experiments. In addition, the entopeduncular neuron was observed to receive convergent inputs from both the caudate nucleus and probably the subthalamic nucleus. Axoaxonal synapses were also found to be involved in the synaptic triad. These results indicate that type I axon terminals originate from the caudate nucleus, part of type IIa and type IV axon terminals originate from the subthalamic nucleus or caudal to the subthalamic nuclear region, and part of type IIa and type IIb terminals come from intrinsic axon collaterals.

Animals↗
PubMed1985

Se-dependent GSH-peroxidase isolated from black sea bass (Centropristis striata).

Black sea bass were injected i.p. with Na2SeO3 (Se-75). A GSH-dependent peroxidase was extracted from the liver via differential centrifugation and gel filtration chromatography. Sea bass liver GSH-peroxidase eluted coincidently with Se-75 and was estimated to have a molecular weight of 72,000. The nature of the selenium-protein bond in the peroxidase was investigated by dialysis vs sodium selenite, glutathione (a sulfhydryl reagent) and alkali. It was concluded that the Se-75 was associated with the peroxidase through a non-sulfhydryl linkage likely to be a C-Se bond. This study confirms that Se is found in a GSH-peroxidase fraction isolated from black sea bass and suggests that Se may play an important role in marine fish.

Animals↗
PubMed1996

Reactions of nitric oxide and peroxynitrite with organic molecules and ferrihorseradish peroxidase: interference with the determination of hydrogen peroxide.

Endothelial, inflammatory, and other cell types, in addition to forming reactive oxygen species, under proper stimulation release free radicals such as nitric oxide (.NO) and strong oxidants such as peroxynitrite (ONOO-), which is the product of the reaction of nitric oxide with superoxide. Several methods for the detection of H2O2 are based on the ferrihorseradish peroxidase catalyzed oxidation of organic molecules. We investigated the reactions of nitric oxide and peroxynitrite with organic molecules as well as with ferrihorseradish peroxidase and examined the potential interference with the detection of H2O2. Peroxynitrite at low concentrations (0-10 microM) induced a concentration-dependent oxidation of 1,2 phenylenediamine, 3-3' dimethoxybenzidine (o-dianisidine) and para-hydroxyphenylacetic acid (pHPA). With the exception of pHPA, the oxidation of the above compounds by peroxynitrite was not affected by the presence of ferrihorseradish peroxidase. The yield of HPA-dimmer, the oxidation product of pHPA by peroxynitrite, was decreased because ferrihorseradish peroxidase catalyzed the formation of a different product, 3-nitro-HPA. Nitrogen oxides, formed by the reaction of nitric oxide with oxygen, oxidized the aromatic amines o-phenylenediamine and o-dianisidine. A 10-fold excess of nitric oxide over H2O2 decreased the yield of pHPA and dihydrorhodamine 123 (DHR123) by 58 and 72%, respectively, as compared to H2O2 plus ferrihorseradish peroxidase. The inhibition of pHPA oxidation by nitric oxide was in part to the reaction of nitric oxide with compound I and compound II and in part due to the reaction with the phenoxyl radical. These data suggest that the simultaneous generation of nitric oxide and peroxynitrite can interfere with the detection of H2O2. The overestimation or underestimation of the H2O2 detected is dependent upon the organic molecule utilized for detection and by the relative rate of nitric oxide, superoxide, and peroxynitrite generation.

Analysis of Variance↗
PubMed2005

Active site structure and catalytic mechanisms of human peroxidases.

Myeloperoxidase (MPO), eosinophil peroxidase, lactoperoxidase, and thyroid peroxidase are heme-containing oxidoreductases (EC 1.7.1.11), which bind ligands and/or undergo a series of redox reactions. Though sharing functional and structural homology, reflecting their phylogenetic origin, differences are observed regarding their spectral features, substrate specificities, redox properties, and kinetics of interconversion of the relevant redox intermediates ferric and ferrous peroxidase, compound I, compound II, and compound III. Depending on substrate availability, these heme enzymes path through the halogenation cycle and/or the peroxidase cycle and/or act as poor (pseudo-)catalases. Based on the published crystal structures of free MPO and its complexes with cyanide, bromide and thiocyanate as well as on sequence analysis and modeling, we critically discuss structure-function relationships. This analysis highlights similarities and distinguishing features within the mammalian peroxidases and intents to provide the molecular and enzymatic basis to understand the prominent role of these heme enzymes in host defense against infection, hormone biosynthesis, and pathogenesis.

Amino Acid Sequence↗
PubMed2006

Disulfide between Cys392 and Cys438 of human serum albumin is redox-active, which is responsible for the thioredoxin-supported lipid peroxidase activity.

Human serum albumin (HSA) is an abundant protein found in blood plasma and extracellular fluids. Previously, we found that HSA has a distinct thioredoxin (Trx)-dependent lipid peroxidase activity in the presence of palmitoyl-CoA. In this paper, we identified the redox-active disulfide, which can be specifically reduced by Trx, responsible for the Trx-dependent lipid peroxidase activity. The IIB-III fragment of HSA (Pro299-Leu585) sustained the Trx-dependent lipid peroxidase activity. Chemical modification of the Trx-reduced IIB-III with a thiol-specific modification agent resulted in a complete loss of the peroxidase activity. The analysis of tryptic-peptides derived from the inactivated HSA and IIB-III revealed that Cys392 and Cys438, which exist as an intramolecular disulfide bond in HSA, were preferentially modified in both HSA and IIB-III. Taken together, these results suggested that HSA has a capability to reduce lipid hydroperoxide with the use of Trx as an in vivo electron donor, and that the redox-active disulfide between Cys392 and Cys438 acts as a primary site of the catalysis for the Trx-linked lipid peroxidase activity.

Binding Sites↗