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PubMed1992

Spectral studies of intermediate species formed in one-electron reactions of bovine liver catalase at room and low temperatures. A comparison with peroxidase reactions.

The reactions of native bovine catalase with superoxide and solvated electrons have been investigated using three different methods for generation of these reducing substrates: gamma-radiolysis of oxygenated or deaerated buffer solutions in the presence of an OH radical scavenger; either xanthine or acetaldehyde with xanthine oxidase; and low-temperature (77 K) gamma-radiolysis of buffered ethylene glycol/water solutions with subsequent annealing of samples at 183 K. The first spectral evidence for catalase compound II formation from native catalase via reaction with superoxide was obtained. The results are compared with results for peroxidase compound II or III formation observed under the same experimental conditions. A scheme is proposed to explain these observations involving intermediate formation of catalase compounds I and III and the ferrous enzyme. The one-electron reduction of catalase and peroxidase by radiolytically-generated solvated electrons was compared. In the present study the first absorption spectrum of a high-spin ferrous catalase which has peaks at 561 and 594 nm is reported, in comparison with a hemochromogen low-spin ferrous peroxidase observed under the same experimental conditions (peaks at 527 and 556 nm). Both spectra were recorded at 77 K. Data presented in this work also provide the first spectral evidence indicating the low temperature (183 K) conversion of high-spin ferrous catalase into compound III (oxycatalase) in the presence of dioxygen. Under the same experimental conditions low-spin ferrous peroxidase was converted into the high-spin ferrous form without oxyperoxidase formation.

Animals↗
PubMed1996

Peroxidase changes in barley induced by ionizing and thermal radiation.

Thermal and ionizing (gamma-ray) radiations were used to induce damage to barley seeds (IB65). The activity and isozyme banding patterns of peroxidase were compared. It was found that both physical agents caused damage to barley seeds (as observed from seedling height), but their action on peroxidase activity is not similar. Gamma-Rays enhance peroxidase activity. Thermal radiation, on the other hand, tends to reduce it but fails to alter the number of peroxidase isozymes. It is conjectured that the pathways of damage by thermal and ionizing radiations are not the same.

Gamma Rays↗
PubMed2002

Thiol-linked peroxidase activity of human sensitive to apoptosis gene (SAG) protein.

SAG (sensitive to apoptosis gene), a novel zinc RING finger protein, which is redox responsive and protects mammalian cells from apoptosis, is a metal chelator and a potential reactive oxygen species (ROS) scavenger, but its antioxidant properties have not been completely defined. Here, we show that SAG possesses a potent peroxidase property to decompose hydrogen peroxide in the presence of dithiothreitol (DTT). However, without DTT as a reducing equivalent, SAG was not able to destroy hydrogen peroxide. The peroxidase activity was completely abolished by the reaction of SAG with N-ethylmaleimide (NEM), a chemical modification agent for the sulfhydryl of proteins. These observations suggested that the sulfhydryl of cysteines in SAG could function as strong nucleophiles to destroy hydrogen peroxide. In addition to the peroxidase activity used to remove hydrogen peroxide, SAG also showed t-butylhydroperoxide (t-BOOH) and fatty acid hydroperoxide-selective peroxidase activity.

Apoptosis↗
PubMed2000

Cadmium inhibition of a structural wheat peroxidase.

The major peroxidase from 15-day-old wheat plants was purified to homogeneity by FPLC ion exchange and molecular exclusion chromatography. It consists of a single polypeptide of M(r) 37,500 according to gel filtration and SDS-PAGE and has a pI of 7.0. Kinetics of pyrogallol peroxidation showed that the enzyme follows the accepted mechanism for peroxidase, with kinetic constants k(1) =4.4x10(6) M(-1) s(-1) and k(3) =8.6x10(5) M(-1) s(-1). The effect of different metal ions was assayed on peroxidase activity. None of the ions used had any effect on enzyme activity, except for Cd(II), which was an inhibitor. This was an unexpected and novel finding for a peroxidase. The kinetics of pyrogallol peroxidation at different concentrations of Cd(II) have been studied and a mechanism for Cd(II) inhibition proposed. The results obtained could explain, in part, cadmium-induced oxidative stress.

Cadmium↗
PubMed1985

Dietary selenium, glutathione peroxidase activity, and toxicity of 2,3,7,8-tetrachloro-dibenzo-p-dioxin.

TCDD has been shown to inhibit selenium-dependent glutathione peroxidase activity. The role of selenium in TCDD toxicity is not known. We have therefore examined the effect of TCDD administration on hepatic glutathione peroxidase, aryl hydrocarbon hydroxylase, glutathione reductase, and glutathione S-transferase activities, glutathione content, and lipid peroxidation in rats fed 0, 0.10, and 2.0 ppm dietary selenium. TCDD treatment significantly inhibited selenium-dependent glutathione peroxidase in animals on diets containing 0.10 and 2.0 ppm selenium. The selenium-dependent glutathione peroxidase activities in rats on 0.10 and 2.0 ppm dietary selenium were 8.3-and 4.7-fold greater than in animals fed a diet containing 0 ppm selenium. TCDD administration enhanced hepatic microsomal lipid peroxidation by factors of 4.0, 4.9, and 9.8 in animals fed diets containing 0, 0.10, and 2.0 ppm selenium, respectively. The administration of a lethal dose of TCDD to rats fed diets containing 0, 0.10, and 2.0 ppm selenium resulted in 0, 46, and 7% survival, respectively, after 66 d. Aryl hydrocarbon hydroxylase, glutathione S-transferase, and glutathione reductase activities were induced by TCDD. The results indicate that optimum dietary selenium provides partial protection from the toxic effects of TCDD.

Animals↗
PubMed1987

Characterization of endocytic compartments using the horseradish peroxidase-diaminobenzidine density shift technique.

We have employed a modification of the horseradish peroxidase (HRP)-diaminobenzidine density shift technique of Courtoy et al. (J. Cell Biol., 1984, 98:870-876) to examine the biochemical properties of the endosome. This organelle is involved in receptor recycling and the sorting of internalized receptor ligand complexes. Transferrin covalently bound to HRP was used to place peroxidase activity specifically within the endosome. The peroxidase-catalyzed polymerization of diaminobenzidine within these vesicles causes an increase in buoyant density, thus allowing them to be separated from other membranes. Using this technique we demonstrate that 125I-low density lipoprotein, 131I-epidermal growth factor, and Tf-HRP are internalized into the same endosome. We discovered that the diaminobenzidine reaction product "cross-links" the lumen of the vesicle, rendering vesicular components detergent insoluble. Furthermore, the reaction inactivates enzymatic activities associated with the endosome. Thus, the diaminobenzidine density shift procedure has limited usefulness in studies designed to isolate endosomal constituents. Nonetheless, we have found that the inactivation of enzymatic activities is confined to those endosomes that contain peroxidase. This selectivity allows us to define endosome-specific activities.

Biological Transport↗
PubMed1967

The ultrastructural basis of capillary permeability studied with peroxidase as a tracer.

The transendothelial passage of horseradish peroxidase, injected intravenously into mice, was studied at the ultrastructural level in capillaries of cardiac and skeletal muscle. Peroxidase appeared to permeate endothelial intercellular clefts and cell junctions. Abnormal peroxidase-induced vascular leakage was excluded. Neutral lanthanum tracer gave similar results. The endothelial cell junctions were considered to be maculae occludentes, with gaps of about 40 A in width between the maculae, rather than zonulae occludentes. Some observations in favor of concurrent vesicular transport of peroxidase were also made. It is concluded that the endothelial cell junctions are most likely to be the morphological equivalent of the small pore system proposed by physiologists for the passage of small, lipid-insoluble molecules across the endothelium.

Animals↗
PubMed1969

Intestinal capillaries. I. Permeability to peroxidase and ferritin.

Horseradish peroxidase (mol. diam. approximately 50 A) and ferritin (mol. diam. approximately 110 A) were used as probe molecules for the small and large pore system, respectively, in blood capillaries of the intestinal mucosa of the mouse. Peroxidase distribution was followed in time, after intravenous injection, by applying the Graham-Karnovsky histochemical procedure to aldehyde-fixed specimens. The tracer was found to leave the plasma rapidly and to reach the pericapillary spaces 1 min post injection. Between 1 min and 1 min 30 sec, gradients of peroxidase reaction product could be demonstrated regularly around the capillaries; their highs were located opposite the fenestrated parts of the endothelium. These gradients were replaced by even distribution past 1 min 30 sec. Ferritin, followed directly by electron microscopy, appeared in the pericapillary spaces 3-4 min after i.v. injection. Like peroxidase, it initially produced transient gradients with highs opposite the fenestrated parts of the endothelium. For both tracers, there was no evidence of movement through intercellular junctions, and transport by plasmalemmal vesicles appeared less efficient than outflow through fenestrae. It is concluded that, in the blood capillaries of the inintestinal mucosa, the diaphragms of the endothelial fenestrae contain the structural equivalents of the small pore system. The large pore system seems to be restricted to a fraction of the fenestral population which presumably consists of diaphragm-free or diaphragm-deficient units.

Animals↗
PubMed1970

Cytochemical localization of endogenous peroxidase in thyroid follicular cells.

Endogenous peroxidase activity in rat thyroid follicular cells is demonstrated cytochemically. Following perfusion fixation of the thyroid gland, small blocks of tissue are incubated in a medium containing substrate for peroxidase, before being postfixed in osmium tetroxide, and processed for electron microscopy. Peroxidase activity is found in thyroid follicular cells in the following sites: (a) the perinuclear cisternae, (b) the cisternae of the endoplasmic reticulum, (c) the inner few lamellae of the Golgi complex, (d) within vesicles, particularly those found apically, and (e) associated with the external surfaces of the microvilli that project apically from the cell into the colloid. In keeping with the radioautographic evidence of others and the postulated role of thyroid peroxidase in iodination, it is suggested that the microvillous apical cell border is the major site where iodination occurs. However, that apical vesicles also play a role in iodination cannot be excluded. The in vitro effect of cyanide, aminotriazole, and thiourea is also discussed.

Animals↗
PubMed1974

The interaction of cationic liposomes containing entrapped horseradish peroxidase with cells in culture.

Cationic liposomes composed of sphingomyelin, cholesterol, and stearylamine were prepared with horseradish peroxidase trapped inside. Stable particles were formed in which 10-12% of the enzymic activity appeared to be located at, or near, the outer surface of the liposome. Adsorption and uptake of liposomes by HeLa cells were followed cytochemically by electron microscopy and quantitated by enzyme assay and by the distribution and fate of particles labeled with [(14)C]cholesterol and [(125)I]horseradish peroxidase. The particles were adsorbed by HeLa cells at least 300 times as efficiently as was free horseradish peroxidase. Many of the particles remained at the cell surface, but numerous membrane-bound cytoplasmic inclusions were observed to contain peroxidase-staining material. In addition, many areas of the cell membrane gave a positive staining reaction. It was concluded that many particles (presumably the larger ones) did not gain access to the interior of the cells, many were phagocytized, and some enzyme was transferred to the cell membrane, perhaps as a result of fusion of the liposomal membrane with the cell membrane.

Adsorption↗
PubMed2003

Graft union formation in tomato plants: peroxidase and catalase involvement.

BACKGROUND AND AIMS: The use of grafted plants in vegetable crop production is now being expanded greatly. However, few data are available on the formation of graft unions in vegetables. In this work, the structural development of the graft union formation in tomato plants is studied, together with the possible relationship with activities of peroxidases and catalases. METHODS: Tomato (Lycopersicon esculentum Mill.) seedlings of cultivar Fanny were grafted on the rootstock of cultivar AR-9704 using the 'tongue approach grafting' method, and were grown in a crop chamber. A study of the structural development of the graft union and the involvement of peroxidases and catalases in the process of graft formation was carried out during the first stages of the graft union (4, 8 and 15 d after grafting). KEY RESULTS: Observation of the structure of the graft union showed formation of xylem and phloem vessels through the graft union 8 d after grafting. In addition, root hydraulic conductance, L0, indicate that the graft union is fully functional 8 d after grafting, which coincided with an increase of peroxidase and catalase activities. CONCLUSIONS: These results suggest that increased peroxidase and catalase activities might be implicated in graft development in tomato plants.

Biomechanical Phenomena↗
PubMed1995

32P-postlabeling analysis of adducts generated by peroxidase-mediated binding of N-hydroxy-4-acetylaminobiphenyl to DNA.

32P-Postlabeling analysis of the bisphosphate derivatives was conducted to characterize the DNA adducts generated from the peroxidase-mediated activation of N-hydroxy-4-acetylaminobiphenyl (N-OH-AABP). Autoradiography of the D1 chromatogram of the postlabeled DNA hydrolysate revealed a major adduct (adduct 1) that migrated at Rf 0.15. An adduct with similar chromatographic characteristics was also obtained by postlabeling the products generated by chemical interaction of: (i) 2',6'-dichlorobenzoyloxy-4-acetylaminobiphenyl with the 3'-monophosphate of deoxyguanosine, and (ii) N-acetoxy-4-acetylaminobiphenyl (N-OAc-AABP) with calf thymus DNA. The adduct derived from chemical reaction exhibited the same mobilities on two-dimensional TLC as that obtained from the peroxidase-mediated DNA binding of N-OH-AABP. Moreover, on HPLC analyses, these bisphosphate derivatives exhibited identical retention times, suggesting that structurally they might be the same. Furthermore, adduct 1 was insensitive to digestion with nuclease P1. In addition to adduct 1, another minor adduct (adduct 2) was also detected in the peroxidase-mediated DNA binding of N-OH-AABP. The adduct 2 in D1 exhibited an Rf of 0.66. Adduct 2 was also observed in the DNA sample chemically interacted with N-OAc-AABP. Both these adducts retained the acetyl moiety, which was confirmed by the presence of radioactivity in the hydrolysate of DNA derived by interaction with N-OAc-[14C-acetyl]AABP (labeled at the N-acetyl group). Based on proton NMR and MS analyses of the 5'-phospho analogs of adducts 1 and 2, the structures of these have been identified as 3-(deoxyguanosine-N2-yl)-4-acetylaminobiphenyl (dG-N2-AABP) and N-(deoxyguanosine-8-yl)-4-acetylaminobiphenyl (dG-C8-AABP). Analyses of the DNA samples obtained from human uroepithelial cells following exposure to N-OH-AABP revealed primarily the non-acetylated derivative N-(deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-ABP) with trace amounts of dG-N2-AABP. These results suggest that in the target cells for 4-aminobiphenyl carcinogenesis, the prevalence of the peroxidase mediated activation reaction of N-OH-AABP is relatively minor compared to the acetyltransferase pathway.

Acetylation↗
PubMed2004

Cytochemical detection of endogenous peroxidase in the intralobular ducts of hamster major salivary glands.

Light and electron microscopic cytochemical investigation of endogenous peroxidase activity in the intralobular ducts of hamster major salivary glands was carried out using the diaminobenzidine-hydrogen peroxidase method. The peroxidase reaction product was localized in the nuclear envelope, the cisternae of the endoplasmic reticulum, the Golgi apparatus and secretory granules in both the intercalated duct cells and the striated duct light cells of all glands. These results suggest the ability of the intralobular duct cells to secrete peroxidase the same as that of acinar cells in hamster salivary glands.

Animals↗
PubMed1989

Biochemical studies of a selenium-deficient population in China: measurement of selenium, glutathione peroxidase and other oxidant defense indices in blood.

Selenium deficiency is necessary for the development of the cardiomyopathy known as Keshan disease. Healthy boys and men (19-22 per group) from a low selenium area (Dechang County) and from an area where sodium selenite was added to salt (Mianning County) were studied. Keshan disease was endemic in Dechang but occurred rarely in Mianning. After an initial blood sampling, each subject received daily selenium supplements (100 micrograms selenium for boys and 200 micrograms for men) as sodium selenate for 14 d. Blood was sampled again at 7 and 14 d. Boys from Dechang had blood selenium levels similar to levels reported for patients with Keshan disease. Plasma glutathione peroxidase activity in boys and men from Dechang was 33 and 43%, respectively, of values from the corresponding groups in Mianning. Comparison of plasma selenium concentrations in boys and men from Dechang gave values of 33 and 38%, respectively, of the corresponding groups in Mianning. Selenium status did not affect red blood cell superoxide dismutase or catalase activities. Plasma vitamin E concentration was below the normal range in all groups but was unaffected by selenium status. Measurements of plasma malondialdehyde revealed no difference between subjects from Dechang and subjects from Mianning. Selenium supplementation raised plasma glutathione peroxidase activity and plasma selenium concentration in all groups. Groups with higher plasma selenium concentration had relatively smaller increases in glutathione peroxidase activity than in selenium concentration. These results characterize the selenium deficiency in subjects at risk for developing Keshan disease. The results obtained with supplementation of selenium indicate the presence of additional plasma forms of selenium besides glutathione peroxidase.

Adolescent↗
PubMed2005

A peroxidase gene expressed during early developmental stages of the parasitic plant Orobanche ramosa.

Broomrapes (Orobanche spp.) are holoparasitic weeds that cause devastating losses in many economically important crops. The molecular mechanisms that control the early stages of host infection in Orobanche are poorly understood. In the present study, the role of peroxidase has been examined during pre-infection growth and development of O. ramosa, using an in vitro model system. Peroxidase activity was histochemically localized at the tips of actively growing radicles and nascent attachment organs. Addition of exogenous catalase resulted in a significant reduction in the apical growth rate of the radicle. The prx1 gene encoding a putative class III peroxidase was cloned from a cDNA library of O. ramosa and was found to be expressed specifically during the early stages of the parasitic life cycle. The exogenous addition of sucrose resulted in significantly reduced prx1 transcript levels and in a dramatic change in radicle development from polarized apical growth to isotropic growth and the formation of tubercle-like structures. The results indicate an important role of peroxidases during the early parasitic stages of Orobanche.

Amino Acid Sequence↗
PubMed2000

Pathways of heterocyclic amine activation in the breast: DNA adducts of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) formed by peroxidases and in human mammary epithelial cells and fibroblasts.

Most human mammary carcinomas originate in the epithelial cells of the breast ducts. A potential role of heterocyclic amines (HAs) in the aetiology of this disease has led us to investigate peroxidase-catalysed and stromal (non-epithelial) activation of the HA 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), which may subsequently lead to DNA damage in the adjacent human mammary epithelial cells (HMECs). HAs are formed when proteinaceous foods are cooked at high temperature and some, but not all, can cause mammary tumours in rats. Myeloperoxidase (MPO) and lactoperoxidase (LPO) are peroxidase enzymes present in breast secretions. (32)P-post-labelling analysis showed that IQ-DNA adducts were formed after co-incubation of IQ (500 microM) with calf thymus DNA, hydrogen peroxide and either bovine LPO or horseradish peroxidase (HRP). The major HRP-mediated IQ-DNA adduct co-migrated on TLC and HPLC with the major adduct formed in HMECs, suggesting a common reactive intermediate (nitrenium ion). IQ-DNA adducts were also formed in extracellular DNA when phorbol myristate acetate-stimulated neutrophils (which activate IQ via MPO) were co-incubated with IQ (500 microM) and extracellular plasmid (4 +/- 1 adducts/10(8) nucleotides) or calf thymus DNA (6 +/- 2). Mean adduct formation was five to seven times greater in neutrophil DNA (31 +/- 20). Primary cultures of human mammary fibroblasts or epithelial cells isolated from reduction mammoplasty tissues (n = 4 individuals) were incubated with IQ (500 microM) and formed 2.5 and 14.8 adducts/10(8) nucleotides (mean values), respectively. Our results indicate the possible contribution of stromal cells and breast peroxidases to the metabolic activation of carcinogens in the mammary gland.

Adult↗
PubMed2000

Enzymic preparation of protein G-peroxidase conjugates catalysed by transglutaminase.

Transglutaminases (TGases, EC 2.3.2.13) have proved to be valuable enzymes for site-directed protein coupling via N(epsilon)-(gamma-L-glutamyl)lysine bonds. Their use in conjugate synthesis would overcome many problems caused by chemical reagents. In this approach, we show for the first time that two proteins with different functionalities, namely soybean peroxidase and protein G, can be cross-linked by bacterial TGase with retention of their activities. Soybean peroxidase and protein G were chosen for the enzymic preparation of a bifunctional conjugate among a series of other TGase substrates detected by enzymic incorporation of small fluorescent or biotinylated molecules. The highest yields of conjugate were obtained with a 15-fold excess of peroxidase in phosphate buffer, pH 7.0. Size exclusion chromatography enabled both purification of the conjugates and recovery of the starting materials. Analysis of bifunctionality revealed the coupling of protein G with an average of three peroxidase molecules.

Cadaverine↗
PubMed1991

One-electron oxidation of Trolox C and vitamin E by peroxidases.

Direct reactions of peroxidases with Trolox C (a vitamin E analogue) and vitamin E were observed in 50% (v/v) methanol. The kinetic results revealed that the reaction of horseradish peroxidase intermediate Compound II with Trolox C and vitamin E was the rate-determining step, and the rate constants were estimated to be 1.7 x 10(3) and 5.1 x 10(2) M-1.s-1, respectively. Peroxidases catalyzed the one-electron oxidation of Trolox C and vitamin E, and the vitamin E phenoxyl radicals resulting from the peroxidase reactions were detected by continuous-flow ESR spectroscopy.

Antioxidants↗