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PubMedDate not supplied

[Inactivation of the human thyroid peroxidase by ultrasound cavitation].

The inactivation kinetics of a human thyroid peroxidase protein fraction upon sonication (ultrasound frequency 27 kHz, power 60 W/cm2) of the enzyme solution in 15 mM phosphate buffer, pH 7.5, was studied. To quantitatively characterize the dependence of the slowest stage of the human thyroid peroxidase inactivation on temperature (36.0-50.4) degrees C, an effective constant of ultrasound inactivation rate Kin(US) was used. From the temperature dependence of Kin(US) at temperatures below 43 degrees C, the activation energy was estimated to be 8.11 kcal/mol. It was shown that the rate of human thyroid peroxidase inactivation strongly depends on the concentration of total protein in solution: the kin(US) value decreases more than sixfold in the protein concentration range from 0.2 to 0.8 mg/ml. It was also shown that poly(2-aminodisulfide-4-nitrophenol), its complexes with human serum albumin as well as the complexes human serum albumin--poly(gallic acid disulfide) substantially inhibit the ultrasound-induced inactivation of the enzyme and can be its effective stabilizers in the ultrasound cavitation field. This confirms the suggestion that active free radicals HO., O2.- and HO2. play a key role in the inactivation of human thyroid peroxidase. A general scheme of the inactivation of human thyroid peroxidase is proposed, which represents a chain of successive and parallel reversible and irreversible elementary steps.

Antioxidants↗
PubMed1975

[Ultrastructural cytochemistry of peroxidase and acid phosphat in mouse eosinophils].

The distribution of peroxidase and acid phosphatase activity in the bone marrow of mouse eosinophils was investigated by electron microscopy. Peroxidase activity was found in the perinuclear space, the endoplasmic reticulum, the Golgi complex, non-mature and mature specific crystal-containing granules. In the course of development peroxidase activity disappears from the cisternal system. In mature eosinophils the enzyme is stored in specific granules, but some of these failed to reveal peroxidase activity. A hypothesis is offered concerning the complete condensation into crystal of the enzyme. In cells incubated in peroxidefree media some granular components stained weakly. Their activity probably depended on the presence of endogenous non-organic peroxidase. In developing eosinophils acid phosphatase was found in the Golgi complex and in non-mature specific granules. In the course of development, acid phosphatase disappears from the granules.

Acid Phosphatase↗
PubMedDate not supplied

[PXD gene controls synthesis of the three anionic peroxidase isoforms in Arabidopsis thaliana].

The pxd mutant of Arabidopsis thaliana had a changed spectrum of anionic peroxidases: three anionic isoforms in the pxd mutant plant had the same enzymatic activity but relatively high electrophoretic mobility as compared to the analogous isoforms in the wild type plants. These isoforms were the most active anionic peroxidases and could be found in most plant organs. Genetic analysis showed that all three isoforms were controlled by the PXD gene. The activity of one isoform was affected by indolyl-3-acetic acid and other stress factors. Expressed sequence tags (EST) analysis of all putative peroxidase genes of A. thaliana revealed the group of the most actively and nonspecifically expressed genes. The promoter sequences of these genes were screened to find the cis-elements. We propose that the PXD gene encodes one of the nonspecific anionic peroxidases or a protein involved in posttranscriptional or posttranslational modification of the peroxidases.

Anions↗
PubMedDate not supplied

[Effect of temperature on structure and functional properties of horseradish peroxidase].

The dynamics of structural and functional changes proceeding in a peroxidase molecule under the effect of temperature was studied. It was shown that peroxidase thermoinactivation proceeds in two consequent stages. Based on the analysis of enzyme peroxidase and oxidase activity and peroxidase spectral and buffer characteristics, it was established that at temperatures from 20 to 55 degrees C reversible conformation there occur changes of the hemoprotein molecule related to consequent unfolding and folding of the protein globule. The influence of temperature of 60 degrees C and above induces the protein globule unfolding and loosing of peroxidase activity.

Armoracia↗
PubMedDate not supplied

[Peroxidase refolding in the presence of specific antibodies].

A panel of eight monoclonal antibodies raised against horseradish root peroxidase has been assembled and characterized. Affinity constants were determined for all antibodies, and their specificity for various structural forms of the enzyme (native peroxidase, apoperoxidase, and denatured peroxidase) were assessed by competitive enzyme immunoassay. The effects of the antibodies on the process of refolding of peroxidase after its denaturing with 6.5 M guanidine hydrochloride were studied spectrophotometrically, by the restoration of the enzymatic activity in the reaction of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate). The yield of the active enzyme in the course of the refolding was increased 1.5 to 1.7 times in the presence of antibody H1. Effects of the antibodies constituting the panel on the activity of native peroxidase and the stability of its dilute solutions were analyzed.

Antibodies, Monoclonal↗
PubMed1991

Thiol and Mn(2+)-mediated oxidation of veratryl alcohol by horseradish peroxidase.

Horseradish peroxidase has been shown to catalyze the oxidation of veratryl alcohol (3,4-dimethoxybenzyl alcohol) and benzyl alcohol to the respective aldehydes in the presence of reduced glutathione, MnCl2, and an organic acid metal chelator such as lactate. The oxidation is most likely the result of hydrogen abstraction from the benzylic carbon of the substrate alcohol leading to eventual disproportionation to the aldehyde product. An aromatic cation radical intermediate, as would be formed during the oxidation of veratryl alcohol in the lignin peroxidase-H2O2 system, is not formed during the horseradish peroxidase-catalyzed reaction. In addition to glutathione, dithiothreitol, L-cysteine, and beta-mercaptoethanol are capable of promoting veratryl alcohol oxidation. Non-thiol reductants, such as ascorbate or dihydroxyfumarate (known substrates of horseradish peroxidase), do not support oxidation of veratryl alcohol. Spectral evidence indicates that horseradish peroxidase compound II is formed during the oxidation reaction. Furthermore, electron spin resonance studies indicate that glutathione is oxidized to the thiyl radical. However, in the absence of Mn2+, the thiyl radical is unable to promote the oxidation of veratryl alcohol. In addition, Mn3+ is unable to promote the oxidation of veratryl alcohol in the absence of glutathione. These results suggest that the ultimate oxidant of veratryl alcohol is a Mn(3+)-GSH or Mn(2+)-GS. complex (where GS. is the glutathiyl radical).

Benzyl Alcohols↗
PubMed2005

Oxidation of an antitumor drug ellipticine by peroxidases.

Ellipticine is a potent antineoplastic agent, whose mode of action is considered to be based mainly on DNA intercalation and/or inhibition of topoisomerase II. Since we found that ellipticine also forms the cytochrome P450 (CYP)-mediated covalent DNA adducts, this anticancer drug is considered to function as a pro-drug, whose pharmacological efficiency and/or genotoxic side effects are dependent on its enzymatic activation in target tissues. Here, we demonstrate that ellipticine is also oxidized by peroxidases, which are abundantly expressed in several target tumor tissues. Lactoperoxidase, myeloperoxidase and horseradish peroxidase were used as models. Peroxidases in the presence of hydrogen peroxide oxidize ellipticine to an ellipticine dimer and N(2)-oxide of ellipticine as the major and minor metabolite, respectively. Inhibition of the peroxidase-mediated ellipticine oxidation by radical scavengers ascorbate, glutathione and NADH suggests a one-electron mechanism of the oxidation. The implication of the oxidation of ellipticine by peroxidases in its mechanism of action is discussed.

Antineoplastic Agents↗
PubMed1991

Catechol oxidation by peroxidase-positive astrocytes in primary culture: an electron spin resonance study.

In rodents, chronic estrogenization has been shown to induce degeneration of dendrites and myelin figures in the hypothalamic arcuate nucleus adjacent to peroxidase-positive astrocyte processes. Because in this brain region estradiol is metabolized to 2-hydroxyestradiol (catecholestrogen), we hypothesized that the latter may be oxidized by the astrocytic peroxidase activity to cytotoxic ortho-semiquinones as occurs in peripheral tissues. Cysteamine induces nonenzymatic peroxidase activity in cultured astroglia identical to that observed in vivo. Using electron spin resonance, we demonstrate robust peroxidase-catalyzed oxidation of 2-hydroxyestradiol and dopamine by cysteamine-pretreated astrocyte cultures relative to untreated controls. These results implicate the peroxidase-positive astrocytes in the pathogenesis of estradiol-related hypothalamic damage, parkinsonism, and other free-radical-related neurologic disorders.

3,3'-Diaminobenzidine↗
PubMed1991

Glutathione S-transferases YcYfetus and YcYc--kinetic and inhibitor studies relating to their glutathione peroxidase activities.

The kinetic properties of the glutathione (GSH) peroxidase activities of GSH S-transferases YcYfetus and YcYc were compared. The catalytic efficiency of the fetal iso-enzyme with cumene hydroperoxide as substrate was approximately four times higher than the other. The effects of the non-substrate ligand rose-Bengal as well as the substrate ligands sulphobromophthalein and acrolein on the GSH peroxidase activity of these two iso-enzymes were also investigated. Depending on the ligand, the inhibition profiles of these two iso-enzymes when measured with either the peroxidase substrate, cumene hydroperoxide or the standard GSH S-transferase substrate 1-chloro-2,4-dinitrobenzene were found to be either very similar (sulphobromophthalein) or markedly different (rose Bengal and acrolein). Significantly, the GSH peroxidase activity of the fetal iso-enzyme was far less susceptible to inhibition by the teratogen, acrolein, than that of the YcYc isoenzyme. It is therefore attractive to suggest that should a similar situation arise in vivo, this resistance to peroxidase inhibition may play a role in preventing the fetotoxic effects of acrolein.

Acrolein↗
PubMed1990

Mechanism of the reaction of ebselen with endogenous thiols: dihydrolipoate is a better cofactor than glutathione in the peroxidase activity of ebselen.

The therapeutic effect of ebselen has been linked to its peroxidase activity. In the present study, the peroxidase activity of ebselen toward H2O2 with the endogenous thiols GSH and dihydrolipoate [L(SH)2] as cofactors was determined. When GSH was used, peroxide removal was described by a ter uni ping pong mechanism with Dalziel coefficients for GSH and H2O2 of 0.165 +/- 0.011 and 0.081 +/- 0.005 mM min, respectively. When L(SH)2 was used, peroxidase activity was independent of the concentration of L(SH)2 in the concentration range studied (5 microM to 2 mM) and peroxide removal was only dependent on the concentration of H2O2 and ebselen, with the second-order rate constant being 12.3 +/- 0.8 mM-1 min-1. To elucidate the difference between GSH and L(SH)2, the molecular mechanism of the peroxidase activity of ebselen was investigated, using UV spectrophotometry, high pressure liquid chromatography, 77Se NMR, and mass spectrometry. GSH was found to react quickly with ebselen to give a selenenyl sulfide, an adduct of GSH to ebselen. Subsequently, the GSH-selenenyl sulfide is converted into the diselenide of ebselen. Finally the diselenide reacts with a peroxide and ebselen is regenerated. The formation by GSH of the diselenide from the GSH-selenenyl sulfide of ebselen is slow and linearly dependent on the concentration of free thiol; however, no net consumption of GSH was observed. Furthermore, it is likely that a selenol is an intermediate in diselenide formation. After reaction between ebselen and L(SH)2 the diselenide of ebselen was immediately detected. The fast formation of the diselenide with L(SH)2 versus the slow formation of the diselenide with GSH accounts for our observation that L(SH)2 is a better cofactor than GSH in the peroxidase activity of ebselen. Our results suggest that the interaction between ebselen and L(SH)2 might be of major importance in the mechanism by which ebselen exerts its therapeutic effect.

Azoles↗
PubMedDate not supplied

[The use of photographic materials as a dry reagent for determining the peroxidase activity of biological preparations].

A new method is reviewed for measuring the peroxidase activity of biopreparations using light quantum-sensitized photographic material as a detector. The method involves the combination of the reactions of peroxidase oxidation of hydroquinone, a constituent part of the developing solutions, by hydrogen peroxide and photochemical interaction of the remaining hydroquinone with silver halogenides of the photoemulsion layer. Visually, up to 2 ng/ml of horse radish peroxidase is detectable. On photometry of the spots obtained, the limit of peroxidase demonstration amounts to 0.6 ng/ml. The data obtained during measurements of the peroxidase activity of the saliva, blood serum, plant extracts and immunoenzymic conjugates are provided.

Humans↗
PubMed1989

The non-flavin redox center of the streptococcal NADH peroxidase. II. Evidence for a stabilized cysteine-sulfenic acid.

Incubation of the streptococcal NADH peroxidase with 5-thio-2-nitrobenzoate under anaerobic denaturing conditions leads to the rapid incorporation of 1 eq/FAD of the aromatic thiol. Addition of dithiothreitol to the resulting conjugate, following ultrafiltration, demonstrates that a mixed disulfide has been formed. Analysis of the denatured NADH peroxidase by iso-electric focusing reveals the presence of two predominant species differing in isoelectric point by approximately 0.1 units. Preincubation with 20 mM hydrogen peroxide gives essentially complete and irreversible conversion to the more acidic species. Treatment of the native peroxidase with low concentrations of hydrogen peroxide also leads to irreversible enzyme inactivation; the low extinction long wavelength absorbance associated with the enzyme as purified is lost in the process. Anaerobic dithionite and NADH titrations of the peroxide-inactivated enzyme indicate that, while the cysteinyl redox center is nonfunctional, the enzyme is still capable of forming a binary complex with NADH. We propose that the redox-active cysteinyl derivative which serves as the second redox center in the native peroxidase is a stabilized cysteine-sulfenic acid derivative of Cys42. This determination is consistent with the covalent modifications observed with both 5-thio-2-nitrobenzoate and with H2O2 and is supported by mass spectrometric analysis of a chymotryptic cysteinyl peptide derived from the unmodified peroxidase.

Amino Acid Sequence↗
PubMed1989

Effects of lead acetate on cerebral glutathione peroxidase and catalase in the suckling rat.

Exposure of immature rats to lead acetate results in hemorrhagic encephalopathy of variable evolution. As the maintenance of adequate protection against peroxides may be critical in this condition, the activities of selenium-glutathione peroxidase and catalase in cerebrum and cerebellum of suckling rats poisoned with lead acetate were studied from day six to day sixteen post-exposure. Age-related decreases of glutathione peroxidase and catalase activities in both controls and lead poisoned animals were observed. An increase in catalase activity was observed in cerebrum and cerebellum of lead-treated rats compared to controls. Glutathione peroxidase activity did not change significantly in cerebrum over the period studied. By contrast, glutathione peroxidase activity in cerebellum of lead-treated rats remained at about twice the control level over most of the study period. This apparent increase in glutathione peroxidase activity may be due either to a slower ontogenic decrease of its specific activity or to enzyme induction in response to oxidant stress in cerebellum.

Animals↗
PubMed1987

Plasma selenium content, platelet glutathione peroxidase and superoxide dismutase activity of residents in Kashin-Beck disease affected area in China.

The activity of platelet glutathione peroxidase, of platelet and erythrocyte superoxide dismutase and the concentration of plasma selenium and vitamin E were measured in two groups of residents in the Kashin-Beck disease affected area and in three from a non-affected area. Average plasma selenium levels and platelet glutathione peroxidase activity were significantly lower in the endemic area than in the non-endemic area, indicating that the residents in the endemic area are indeed in a low selenium status. There existed a significantly positive correlation, r = 0.94, n = 78, p less than 0.001, between platelet glutathione peroxidase activity and plasma selenium concentration over a range from 2 to 79 micrograms/L (mean values 5 to 66 micrograms/L). Platelet glutathione peroxidase also correlated well with plasma selenium in each group of residents with varying plasma selenium levels, demonstrating that determination of glutathione peroxidase activity in platelets can be used as an indicator for assessing low selenium status in humans. No significant difference of vitamin E levels was observed between the residents in the endemic and non-endemic areas. There were no statistically significant differences in the activity of superoxide dismutase between each two groups studied, showing that superoxide dismutase does not undergo a compensatory increase in the residents of low selenium status.

Adolescent↗
PubMed1987

Effects of combined treatments with selenium, glutathione, and vitamin E on glutathione peroxidase activity, ornithine decarboxylase induction, and complete and multistage carcinogenesis in mouse skin.

Several structurally different tumor promoters altered to various degrees both glutathione (GSH) peroxidase (EC 1.11.1.9) and ornithine decarboxylase (ODC, L-ornithine carboxy-lyase, EC 4.1.1.17) activities in mouse epidermis in vivo. At 5 h after their application to the skin, the complete tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and the stage 2 promoter mezerein were the most potent in inhibiting GSH peroxidase activity and inducing ODC activity. In comparison, the effects of anthralin, phorbol-12,13-didecanoate, benzoyl peroxide, H2O2, and phorbol-12,13-dibenzoate were much smaller, whereas the nontumor promoter phorbol, the hyperplastic agent ethyl phenylpropiolate, and the stage 1 promoter 4-O-methyl TPA did not alter GSH peroxidase and ODC activities. Various treatments including i.p. injections of 40 micrograms of Na2SeO3 and 100 mumol of GSH and/or topical applications of 40 mumol of D-alpha-tocopherol (vitamin E) 20 or 15 min, respectively, before tumor promoter treatment inhibited in an additive manner the effects of either TPA or mezerein on both GSH peroxidase activity and ODC induction. Moreover, these Na2SeO3, GSH, and/or vitamin E treatments inhibited in the same additive manner the tumor-promoting activity of TPA in the initiation-promotion protocol. However, when tested in the 2-stage promotion protocol with 4 doses of TPA followed by twice weekly applications of mezerein, Na2SeO3 plus vitamin E and GSH plus vitamin E treatments inhibited remarkably the tumor-promoting activity of mezerein but were ineffective in the first stage of promotion. The sequence and magnitude for the effects of 7,12-dimethylbenz[alpha]anthracene (DMBA) on GSH peroxidase and ODC activities were very different from those of the tumor promoters. In contrast with their antitumor-promoting activity, the treatments with Na2SeO3 plus vitamin E and GSH plus vitamin E failed to inhibit the carcinogenicity of a single large dose of DMBA and even enhanced the induction of skin tumors by repeated applications of subcarcinogenic doses of DMBA. These results suggest that the promoting component of DMBA carcinogenesis may be different from that of TPA. Moreover, the anticarcinogenicity of Na2SeO3, GSH, and vitamin E may be linked to their ability to facilitate or enhance the activity of the natural GSH-dependent antioxidant protective system of the epidermal cells during the later stages of skin tumor promotion.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Purification and characterization of a novel monomeric glutathione peroxidase from rat liver.

A novel glutathione peroxidase, which is active toward hydroperoxides of phospholipid in the presence of a detergent, has been purified to homogeneity from a rat liver postmicrosomal supernatant fraction by ammonium sulfate fractionation and three different column chromatographies. From a DE52 column, glutathione peroxidase active toward phosphatidylcholine dilinoleoyl hydroperoxides was eluted in one major and two minor peaks. The enzyme in the major peak was found to be separated from the "classic" glutathione peroxidase and glutathione S-transferases and further purified by Sephacryl S-200 and Mono Q column chromatographies. The purified enzyme was found to be homogeneous on polyacrylamide gel electrophoresis under nondenaturing conditions as well as that in the presence of sodium dodecyl sulfate. The molecular weight of the enzyme as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 22,000, and that by gel filtration was comparable, indicating that the enzyme protein is a single polypeptide. The purified enzyme was found to catalyze the reduction of phosphatidylcholine dilinoleoyl hydroperoxides to the corresponding hydroxy derivatives. The isoelectric point of the enzyme was found at pH 6.2, and the optimum pH for the enzyme activity was 8.0. The enzyme was active toward cumene hydroperoxide, H2O2, and 1-monolinolein hydroperoxides in the absence of a detergent. The enzyme activity toward phospholipid hydroperoxides was minute in the absence of a detergent but was remarkably enhanced by the addition of a detergent. From these results, the presently purified enzyme is obviously different from the classic glutathione peroxidase and also from phospholipid hydroperoxide glutathione peroxidase purified from pig heart (Ursini, F., Maiorino, M., and Gregolin, C. (1985) Biochim. Biophys. Acta 839, 62-70), though considerably similar to the latter.

Animals↗
PubMed1979

[Peroxidase activity of hemoglobin, modified at the carboxylic groups of heme and amino acids].

The effects of modification of heme carboxylic groups by omega-aminoenantic acid and L-phenylalamine on the peroxidase activity of hemoglobin were studied. For this purpose the peroxidase activities of the original compounds--hemin, hemin-aminoenantic acid, hemin-phenylalanine and hemoglobins prepared from the hemin and globin compounds--hemoglobin, aminoenantyl-hemoglobin and phenylalanine hemoglobin--were determined. The dependence of the peroxidase activity of these compounds on their concentrations and pH was analyzed. It was shown that 40--50% modification of the heme carboxylic groups by amino acids decreases the peroxidase activity of the modified hemins and that of modified hemoglobins reconstructed from these hemins and globin. A decrease of the catalytic activity of the hemoglobin derivatives is due to a lower peroxidase activity (as compared to hemin) of the modified hemins. It is thus concluded that the amino acid modification of the carboxylic groups of heme does not affect the heme-protein interactions in the hemoglobin molecule.

Amino Acids↗
PubMed1985

Effect of gold on selenium and glutathione peroxidase activities in rat tissues.

Gold (Au) thioglucose, used to treat inflammatory diseases such as rheumatoid arthritis, inhibits the selenium (Se)-dependent glutathione peroxidase. The present study examines the ability of Au to act either as a Se antagonist or as a GSH peroxidase inhibitor in vivo. The effects of gold thioglucose loading on Se distribution, and on Se-dependent GSH peroxidase and GSH S-transferase, were examined in rats fed three dietary levels of Se (0, 0.2, and 2.0 ppm), and with or without adjuvant-induced inflammation. Kidney, liver, spleen, testes, and erythrocytes were selected for study based upon their high Se content and their ability to concentrate Au. Au loading increased kidney, liver, and spleen Se concentrations, and this effect was dependent upon dietary Se levels. Rats fed Se-supplemented diets had higher levels of Au in kidney, liver, and spleens than did rats fed a Se-deficient diet. Au loading decreased GSH peroxidase activity in kidney, liver, and erythrocytes. The decrease in GSH peroxidase in kidney and liver, and the increase in Se concentration in these tissues, suggest that Au-Se complexes may have limited the biosynthesis of the enzyme. Au affects Se distribution, and Se concentrates Au in tissues with a high lysosomal content.

Animals↗