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 703 records · Page 39Linked to original sources
PubMed1985

Structure of an electron transfer complex. I. Covalent cross-linking of cytochrome c peroxidase and cytochrome c.

Cytochrome c peroxidase and cytochrome c form a noncovalent electron transfer complex in the course of the peroxidase-catalyzed reduction of H2O2. The two hemoproteins were cross-linked in 40% yield to a covalent 1:1 complex with the aid of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The covalent complex was found to be a valid model of the noncovalent electron transfer complex for the following reasons. The covalent complex had only 5% residual peroxidase activity toward exogeneous ferrocytochrome c indicating that the cross-linked cytochrome c covers the electron-accepting site of cytochrome c peroxidase. The residual peroxidase activity was almost independent of ionic strength indicating that the electron-accepting site is much less accessible even when ionic bonds between the two cross-linked hemoproteins are severed. The rate of reduction of heme c by ascorbate is 15 times slower in the covalent complex than in free cytochrome c and is independent of ionic strength. Although the covalent complex may not have been entirely pure with respect to the number and location of the cross-links, two major cross-links could be localized to within a few residues. One is from Lys 13 of cytochrome c to an acidic residue in positions 32, 33, 34, 35, or 37 of cytochrome c peroxidase, the other from Lys 86 of cytochrome c to a carboxyl group in the same cluster of acidic residues. The result stresses the importance of a peculiar stretch of acidic residues of cytochrome c peroxidase and of Lys 13 and 86 of cytochrome c.

Animals↗
PubMed1986

Cervicovaginal peroxidases: markers of the fertile period.

The specific activity of guaiacol peroxidase was measured daily in human cervical mucus, vaginal fluids, and saliva during 45 cycles in 31 women. Also determined were basal body temperatures and serum hormones (luteinizing hormone [LH], estradiol, progesterone). The guaiacol peroxidase was extracted with 0.5 M CaCl2 and thus may be a different peroxidase from that obtained by noncalcium extraction procedures. The guaiacol peroxidase specific activity did not vary in the saliva during the cycle but fell sharply in the cervical mucus and vaginal fluid four to five days before the ovulation time, estimated by the LH peak, and rose again one to two days after ovulation. Anovulatory cycles did not show the midcycle drop in guaiacol peroxidase. Growth curve analysis gave excellent fitting of the guaiacol peroxidase data to a polynominal model. These data suggest that cervicovaginal guaiacol peroxidase may be clinically useful in detecting the fertile period for population control and for infertility treatment.

Adult↗
PubMed1986

Characterization of one- and two-electron oxidations of glutathione coupled with lactoperoxidase and thyroid peroxidase reactions.

Glutathione (GSH) was oxidized to GSSG in the presence of H2O2, tyrosine, and peroxidase. During the GSH oxidation catalyzed by lactoperoxidase, O2 was consumed and the formation of glutathione free radical was confirmed by ESR of its 5,5'-dimethyl-1-pyrroline-N-oxide adduct. When lactoperoxidase was replaced by thyroid peroxidase in the reaction system, the consumption of O2 and the formation of the free radical became negligibly small. These results led us to conclude that, in the presence of H2O2 and tyrosine, lactoperoxidase and thyroid peroxidase caused the one-electron and two-electron oxidations of GSH, respectively. It was assumed that GSH is oxidized by primary oxidation products of tyrosine, which are phenoxyl free radicals in lactoperoxidase reactions and phenoxyl cations in thyroid peroxidase reactions. When tyrosine was replaced by diiodotyrosine or 2,6-dichlorophenol, the difference in the mechanism between lactoperoxidase and thyroid peroxidase disappeared and both caused the one-electron oxidation of GSH. Iodides also served as an effective mediator of GSH oxidation coupled with the peroxidase reactions. In this case the two peroxidases both caused the two-electron oxidation of GSH.

Animals↗
PubMed1983

Peroxidase metabolism of the urinary bladder carcinogen 2-amino-4-(5-nitro-2-furyl)thiazole.

Metabolism of 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) by a variety of different peroxidases was examined. Metabolism of ANFT was measured by the binding of radiolabeled substrates to protein and DNA. Prostaglandin hydroperoxidase but not horseradish peroxidase, lactoperoxidase, or chloroperoxidase metabolically activated ANFT. All four peroxidases catalyzed the binding of benzidine to protein and DNA. With peroxide substrates, peroxidase-catalyzed binding of both carcinogens was observed with or without molecular oxygen. Arachidonic acid-dependent binding of ANFT and benzidine by prostaglandin endoperoxide synthetase was inhibited by anaerobic conditions and aspirin. Chloroperoxidase activation of benzidine was also inhibited by aspirin. Vitamin E inhibited activation of both carcinogens by all enzymes examined. Prostaglandin hydroperoxidase-catalyzed binding of benzidine to protein was inhibited by the 5-nitrofurans ANFT and 3-hydroxymethyl-1-(([3-(5-nitro-2-furyl)allydidene] amino))hydantoin and acetaminophen, while only acetaminophen inhibited horseradish peroxidase-catalyzed binding. These results indicate that different peroxidases may exhibit specificity with respect to their activation of carcinogens. Only prostaglandin hydroperoxidase activated the 5-nitrofuran ANFT, while a number of peroxidases activated the aromatic amine benzidine.

Anaerobiosis↗
PubMed1984

Mechanism of iodide-dependent catalatic activity of thyroid peroxidase and lactoperoxidase.

Mechanisms that have been proposed for peroxidase-catalyzed iodination require the utilization of 1 mol of H2O2 for organic binding of 1 mol of iodide. When we measured the stoichiometry of this reaction using thyroid peroxidase or lactoperoxidase at pH 7.0, we consistently obtained a ratio less than 1.0. This was shown to be attributable to catalase-like activity of these enzymes, resulting in unproductive cleavage of H2O2. This catalatic activity was completely iodide-dependent. To elucidate the mechanism of the iodide-dependent catalatic activity, the effects of various agents were investigated. The major observations may be summarized as follows: 1) The catalatic activity was inhibited in the presence of an iodine acceptor such as tyrosine. 2) The pseudohalide, SCN-, could not replace I- as a promoter of catalatic activity. 3) The inhibitory effects of the thioureylene drugs, methimazole and carbimazole, on the iodide-dependent catalatic activity were very similar to those reported previously for thyroid peroxidase-catalyzed iodination. 4) High concentrations of I- inhibited the catalatic activity of thyroid peroxidase and lactoperoxidase in a manner similar to that described previously for peroxidase-catalyzed iodination. On the basis of these observations and other findings, we have proposed a scheme which offers a possible explanation for iodide-dependent catalatic activity of thyroid peroxidase and lactoperoxidase. Compound I of the peroxidases is represented as EO, and oxidation of I- by EO is postulated to form enzyme-bound hypoiodite, represented in our scheme as [EOI]-. We suggest that the latter can react with H2O2 in a catalase-like reaction, with evolution of O2. We postulate further that the same form of oxidized iodine is also involved in iodination of tyrosine, oxidation of thioureylene drugs, and oxidation of I-, and that inhibition of catalatic activity by these agents occurs through competition with H2O2 for oxidized iodine.

Animals↗
PubMed1981

[Inhibition and inactivation of horseradish peroxidase by thiourea].

The kinetics of horseradish peroxidase (EC 1.11.1.7)-catalyzed oxidation of o-dianisidine by hydrogen peroxide in the presence of thiourea were studied. At the first, fast step of this process thiourea acts as a competitive reversible inhibitor with respect to o-dianisidine (Ki = 0.22 mM). The formation of a thiourea-peroxidase complex was determined by the increase in the absorbance at A495 and A638 of the enzyme. The dissociation constant for the peroxidase-thiourea complex is equal to 2.0-2.7 mM. Thiourea is not a specific substrate of peroxidase during the oxidation reaction by H2O2, but is an oxidase substrate (although not a very active one) of peroxidase. The irreversible inactivation of the enzyme during its incubation with thiourea was studied. The first-order inactivation rate constant (kin) was shown to increase with a fall in the enzyme concentration. The curve of the dependence of kin on the initial concentration of thiourea shows a maximum at 5-7 mM. The enzyme inactivation is due to its modification by intermediate free radical products of thiourea oxidation. The inhibitors of the free radical reactions (o-dianisidine) protect the enzyme against inactivation. The degree of inactivation depends on concentrations and ratio of thiourea and peroxidase. A possible mechanism of peroxidase interaction with thiourea is discussed.

Horseradish Peroxidase↗
PubMed1983

The liver hemopoietic environment: II. Peroxidase reactive mouse fetal liver hemopoietic cells.

Through the combined use of peroxidase cytochemistry and examination at the ultrastructural level, the present study has identified liver hemopoietic foci containing three forms of erythropoietic cells, two forms of myelopoietic cells, and a population of peroxidase nonreactive cells within the extravascular compartments of mouse fetal liver. The nonreactive cells were 10 micron in diameter, displayed no peroxidase activity and were designated type I cells. This cell had an irregular nucleus, small profiles of rough endoplasmic reticulum (RER), a considerable population of monoribosomes and a few polyribosomes. The incidence of this cell type decreased significantly from 50% at 12 days gestation to approximately 10% of the hemopoietic cells at 17 days gestation. Type I cells could not be classified into a hemopoietic lineage and may represent undifferentiated hemopoietic stem cells. Three forms of erythropoietic cells, designated types II, III, and IV, were identified. These cells had a diffuse cytoplasmic peroxidase reaction, no peroxidase positive membrane-bound organelles, and were approximately 7 micron in diameter. They corresponded to the more classically defined proerythroblast, polychromatophilic erythroblast, and nucleated normoblast, respectively. Types II and III had moderate cytoplasmic reactions, whereas type III, in addition, had a slight nuclear reaction. Type IV cells had a very dense cytoplasmic reaction but no nuclear reaction. Of the myelopoietic cells detected, one form had a slightly reactive Golgi and a few reactive granules. The other form possessed a clearly positive nuclear envelope (NE), RER, Golgi, and a population of reactive granules. The phagocytic sinusoidal lining cells (Kupffer cells) were peroxidase negative in contrast to similar cells in the rat. A population of peroxidase-positive granules was detected in fetal liver developing hepatocytes at 17 days gestation and increased in number with age. The morphology and organization of these various cell types in the liver hemopoietic environment are discussed.

Animals↗
PubMed1993

Chronology of peroxidase activity in the developing rat parotid gland.

The course of development of salivary peroxidase, an enzyme that has an important role in oral defense mechanisms, has been well documented in rat submandibular glands. However, the only report on salivary peroxidase activity in the other major salivary glands of the rat has been a cytochemical study of the adult parotid gland. In the present investigation, the accumulation of salivary peroxidase activity in developing parotid glands of rats was followed both biochemically and cytochemically. Specific activity (units per mg protein) attributable to salivary peroxidase began at 1 day after birth, then rose rapidly but unevenly, with peaks at 21 and 70 days, and no difference between the sexes at any age. Activity per gland increased progressively to 42 days in both sexes and was significantly higher in males at 70 days. The cytochemical observations on peroxidase activity localized to the rough endoplasmic reticulum and secretory granules of the developing acini were well correlated with the biochemical findings. Peroxidase-negative cells occurred in immature acini at 1 and 7 days, but only in the intercalated ducts thereafter. This observation suggests that the acini are a source of some of the ductal cells, at least during early postnatal development. The developmental pattern of specific activity differed from those of other rat parotid secretory enzymes, indicating that control of their synthesis during development is noncoordinate. The patterns of specific activity of the parotid and submandibular glands were complementary, suggesting that their combined secretions may supply biologically significant peroxidase activity to the oral cavities of rats throughout postnatal development.

Animals↗
PubMed1989

Effect of molecular charge on para- and transcellular access of horseradish peroxidase into rat bile.

The permeability pathway into the biliary tree for small inert molecules exhibits a charge selectivity. Using a method which distinguishes trans- from paracellular access, we have examined the charge selectivity of biliary access pathways for the 40-kD protein horseradish peroxidase (pI 7.5), which was derivatized to strongly anionic (pI less than 3.5) and strongly cationic (pI greater than 9.5) isoenzymes. Each isoenzyme was injected as a bolus into the perfusate of an isolated rat liver perfused in situ with a nonrecirculating Krebs-Ringer buffer. Bile was collected at intervals and horseradish peroxidase activity was measured. Its appearance allowed differentiation of paracellular from transcellular access, and the amount entering via each pathway was quantified. The species of enzyme entering bile was the same as that injected as determined by cation-exchange high-performance liquid chromatography of biliary horseradish peroxidase. Paracellular biliary access of anionic horseradish peroxidase was less than 50% that of neutral and cationic horseradish peroxidase both in the control state and when paracellular entry was augmented with 10(-10) M vasopressin. Transcellular access of anionic horseradish peroxidase was similarly restricted. To determine whether this restriction of anionic transcellular access was brought about by diminished hepatocellular uptake or augmented catabolism, we studied these parameters in 4-hr primary hepatocyte cultures. The uptake rates of all species were similar. Little or no degradation or efflux of any horseradish peroxidase species occurred over 30 min in the cultured cells. We conclude that access is charge selective for macromolecules and that this selectivity holds for trans- as well as for paracellular pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Role of glutathione peroxidase in protecting mammalian spermatozoa from loss of motility caused by spontaneous lipid peroxidation.

Mouse and human spermatozoa, but not rabbit spermatozoa, have long been known to be sensitive to loss of motility induced by exogenous H2O2. Recent work has shown that loss of sperm motility in these species correlates with the extent of spontaneous lipid peroxidation. In this study, the effect of H2O2 on this reaction in sperm of the three species was investigated. The rate of spontaneous lipid peroxidation in mouse and human sperm is markedly enhanced in the presence of 1-5 mM H2O2, while the rate in rabbit sperm is unaffected by H2O2. The enhancement of lipid peroxidation, the rate of reaction of H2O2 with the cells, the activity of sperm glutathione peroxidase, and the endogenous glutathione content are highest in mouse sperm, intermediate in human sperm, and very low in rabbit sperm. Inactivation of glutathione peroxidase occurs in the presence of H2O2 due to complete conversion of endogenous glutathione to GSSG: No GSH is available as electron donor substrate to the peroxidase. Inactivation of glutathione peroxidase by the inhibitor mercaptosuccinate has the same effect on rate of lipid peroxidation and loss of motility in mouse and human sperm as does H2O2. This implies that H2O2 by itself at 1-5 mM is not intrinsically toxic to the cells. With merceptosuccinate, the endogenous glutathione is present as GSH in mouse and human sperm, indicating that the redox state of intracellular glutathione by itself plays little role in protecting the cell against spontaneous lipid peroxidation. Mouse and human sperm also have high rates of superoxide production. We conclude that the key intermediate in spontaneous lipid peroxidation is lipid hydroperoxide generated by a chain reaction initiated by and utilizing superoxide. Removal of this hydroperoxide by glutathione peroxidase protects these sperm against peroxidation; inactivation of the peroxidase allows lipid hydroperoxide to increase and so increases the peroxidation rate. Rabbit sperm have low rates of superoxide reaction due to high activity of their superoxide dismutase; lack of endogenous glutathione and low peroxidase activity does not affect their rate of lipid peroxidation. As a result, these sperm are not affected by either H2O2 or mercaptosuccinate. These results lead us to postulate a mechanism for spontaneous lipid peroxidation in mammalian sperm which involves reaction of lipid hydroperoxide and O2 as the rate-determining step.

Animals↗
PubMed1994

Demonstration of glutathione peroxidase in rat liver peroxisomes and its intraorganellar distribution.

Earlier, we reported that rat liver peroxisomes contain Cu-Zn superoxide dismutase (J. Biol. Chem. 267, 6870), thereby suggesting a new antioxidant role for this organelle in free radical metabolism. In this study, we report for the first time that mammalian peroxisomes also contain glutathione peroxidase. Using highly purified rat liver peroxisomes isolated by Nycodenz gradient, we found that peroxisomes contain glutathione peroxidase which shows enzymatic activity with different substrates such as hydrogen peroxide, cumene hydroperoxide, and t-butyl hydroperoxide. This activity could be inhibited in vitro by mercaptosuccinate. Western blot analysis revealed that peroxisomes from control and ciprofibrate-treated livers show immunoreactive bands with antibodies raised against glutathione peroxidase. The intraperoxisomal distribution of glutathione peroxidase was investigated by using peroxisomal membrane and matrix proteins. The results revealed that glutathione peroxidase is a matrix enzyme. The presence of glutathione peroxidase in peroxisomes provides an alternate enzyme system responsible for the degradation of organic peroxides and the degradation of H2O2 under conditions in which catalase is inactivated (e.g., ischemia-reperfusion and endotoxemia). These findings suggest that glutathione peroxidase in peroxisomes may play a novel role in the cellular antioxidant responses to various oxidative stress conditions.

Animals↗
PubMed1996

Heterologous expression and reconstitution of fungal Mn peroxidase.

We have optimized the conditions under which recombinant Mn peroxidase from the white-rot fungus Phanerochaete chrysosporium can be expressed in Escherichia coli. A bacterial expression vector for the cDNA of Mn peroxidase isozyme H4 (lambda MP1) was constructed (R. E. Whitwam, I. G. Gazarian, and M. Tien, Biochem. Biophys. Res. Commun. 216, 1013-1017, 1995) whose expression in E. coli results in the formation of catalytically inactive polypeptide which can be refolded to active enzyme. The refolded enzyme was purified to homogeneity. Refolding was most efficient in 2 M urea, pH 8.0, and was absolutely dependent upon the presence of CaCl2, hemin, and oxidized glutathione. The recombinant enzyme had the same spectral and kinetic properties as the native fungal enzyme. The Km of recombinant Mn peroxidase for substrates H2O2 and the Mn2+/oxalate complex are 100 and 52 microM, respectively. The kcat as measured by Mn3+/oxalate formation is 450 s-1. These are essentially the same values as seen with the native fungal enzyme. The rate of formation of compound I, the two-electron-oxidized state of the enzyme, is 4.0 x 10(6) M-1 s-1, identical to the rate of the native fungal Mn peroxidase. The reaction of compound I with Mn2+ is too fast to measure at pH 4.5 in the recombinant Mn peroxidase. At a suboptimal pH of 2.5 a rate of 4.2 x 10(4) M-1 s-1 is obtained for the recombinant enzyme. The reaction of compound II, the one-electron-oxidized state of the enzyme, with Mn2+/oxalate has a Kd of 13 microM and a first-order rate constant of 230 s-1 in the recombinant enzyme. These rates are essentially the same as those seen with the native fungal MnP. These results demonstrate that the bacterial expression of recombinant Mn peroxidase is a convenient and efficient system for the expression and characterization of Mn peroxidase.

Agaricales↗
PubMed1999

The crystal structure of lignin peroxidase at 1.70 A resolution reveals a hydroxy group on the cbeta of tryptophan 171: a novel radical site formed during the redox cycle.

The crystal structure of lignin peroxidase (LiP) from the white rot fungus Phanerochaete chrysosporium was refined to an R-factor of 16.2 % utilizing synchrotron data in the resolution range from 10 to 1.7 A. The final model comprises all 343 amino acid residues, 370 water molecules, the heme, four carbohydrates, and two calcium ions. Lignin peroxidase shows the typical peroxidase fold and the heme has a close environment as found in other peroxidases. During refinement of the LiP model an unprecedented modification of an amino acid was recognized. The surface residue tryptophan 171 in LiP is stereospecifically hydroxylated at the Cbeta atom due to an autocatalytic process. We propose that during the catalytic cycle of LiP a transient radical at Trp171 occurs that is different from those previously assumed for this type of peroxidase. Recently, the existence of a second substrate-binding site centered at Trp171 has been reported, by us which is different from the "classical heme edge" site found in other peroxidases. Here, we report evidence for a radical formation at Trp171 using spin trapping, which supports the concept of Trp171 being a redox active amino acid and being involved in the oxidation of veratryl alcohol. On the basis of our current model, an electron pathway from Trp171 to the heme is envisaged, relevant for the oxidation of veratryl alcohol and possibly lignin. Beside the opening leading to the heme edge, which can accommodate small aromatic substrate molecules, a smaller channel giving access to the distal heme pocket was identified that is large enough for molecules such as hydrogen peroxide. Furthermore, it was found that in LiP the bond between the heme iron and the Nepsilon2 atom of the proximal histidine residue is significantly longer than in cytochrome c peroxidase (CcP). The weaker Fe-N bond in LiP renders the heme more electron deficient and destabilizes high oxidation states, which could explain the higher redox potential of LiP as compared to CcP.

Benzyl Alcohols↗
PubMed1979

Steroid hormone regulations of uterine peroxidase activity.

Uterine peroxidase enzyme activity has been studied as a marker for estrogen action in the uterus to help clarify the mechanism of estrogen action and its modulation by antiestrogens and progestins. Estrogen-induced increases in peroxidase were found to closely parallel increases in uterine weight and DNA content in the castrate rat. In the cycling female rat, uterine peroxidase levels were highest during proestrus and estrus and the lower levels of metestrous and diestrous uteri could be raised to estrous levels by administration of estrogen. However, the estrous levels were not further increased by estrogen treatment. The antiestrogen, CI628, while a very weak inducer of uterine peroxidase, is an effective antagonist of the estrogen induction of the enzyme. The prolonged duration of this CI628-effected inhibition corresponds to the prolonged depletion of cytoplasmic estrogen receptor seen with CI628 treatment. Progesterone, R5020 and norethindrone were also found to be effective antagonists of estrogen-induced uterine peroxidase. Medrogestone and clogestrone, less potent progestins in the rat, were also less effective antagonists of peroxidase induction. Since progesterone was found to inhibit peroxidase induction due to both estrone and diethylstilbestrol, as well as estradiol, it is considered unlikely that this antagonism relates to progestin-induced increases in uterine 17 beta-hydroxysteroid dehydrogenase. Rather, it is proposed that progestins, acting through progestin receptor, may have a more direct role, possibly acting at the level of the genome to repress the expression of estrogen-induced products.

Animals↗
PubMed1977

Cross-linking of protein by peroxidase.

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

2-Aminoadipic Acid↗
PubMed1992

cDNA, amino acid and carbohydrate sequence of barley seed-specific peroxidase BP 1.

The major peroxidase of barley seed BP 1 was characterized. Previous studies showed a low carbohydrate content, low specific activity and tissue-specific expression, and suggested that this basic peroxidase could be particularly useful in the elucidation of the structure-function relationship and in the study of the biological roles of plant peroxidases (S.K. Rasmussen, K.G. Welinder and J. Hejgaard (1991) Plant Mol Biol 16: 317-327). A cDNA library was prepared from mRNA isolated from seeds 15 days after flowering. Full-length clones were obtained and showed 3' end length variants, a G+C content of 69% in the translated region, a 90% G or C preference in the wobble position of the codons and a typical signal peptide sequence. N-terminal amino acid sequencing and sequence analysis of tryptic peptides verified 98% of the sequence of the mature BP 1 which contains 309 amino acid residues. BP 1 is the first characterized plant peroxidase which is not blocked by pyroglutamate. BP 1 polymorphism was observed. BP 1 is less than 50% identical to other plant peroxidases which, taken together with its developmentally dependent expression in the endosperm 15-20 days after flowering, suggests a unique biological role of this enzyme. The barley peroxidase is processed at the C-terminus and might be targeted to the vacuole. The single site of glycosylation is located near the C-terminus in the N-glycosylation sequon -Asn-Cys-Ser- in which Cys forms part of a disulphide bridge. The major glycan is a typical plant modified-type structure, Man alpha 1-6(Xyl beta 1-2)Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-3)GlcNAc. The BP 1 gene was RFLP-mapped on barley chromosome 3, and we propose Prx5 as the name for this new peroxidase locus.

Amino Acid Sequence↗
PubMed1996

Peroxidase deficiency of nickel-transformed hamster cells correlates with their increased resistance to cytotoxicity of peroxides.

Using a procedure aimed at isolation of genes that are inactivated during nickel-induced carcinogenesis in Chinese hamster cells, a homolog of genes encoding human and mouse heme containing peroxidases has been cloned. Northern blot analysis of normal cultured fibroblasts and two nickel-transformed cell lines confirmed that this gene was expressed in normal but not in transformed cells. Nickel-transformed cells also tested negative for peroxidase activity using a sensitive fluorescence assay. Cultured embryo cells or fibroblasts that express peroxidase activity and their nickel-transformed peroxidase-deficient counterparts were employed to investigate the role of peroxidase-catalyzed processes in cytotoxicity induced by tert-butyl hydroperoxide or cumene hydroperoxide. It has been found that peroxidase-deficient cells were significantly more resistant to cytotoxic effect of these compounds suggesting that cytotoxic effect of hydroperoxides may be mediated in part by free radicals generated in the course of peroxidase-catalyzed reactions.

Animals↗
PubMed1987

Immunological characterization of soluble peroxidases from rat tissues including preputial gland.

A highly active soluble peroxidase has been identified in the preputial gland of rats and characterized immunologically along with other soluble peroxidases of a number of rat tissues such as submaxillary gland, exorbital lacrimal gland and also of the uterine fluid of the estrogen treated rats. All these peroxidases have the native molecular weight around 73K as determined by gel filtration on Sephadex G-150. An antiserum raised against the pure bovine lactoperoxidase interacts with all these soluble peroxidases and immunoprecipitates the enzyme activity in a similar fashion when titrated against varied concentration of the antiserum. Following electrophoretic transfer to nitrocellulose by Western blotting, the antiserum crossreacts with the preputial, submaxillary and lacrimal gland protein of molecular weight around 73K and with the uterine fluid protein of molecular weight of 80K. An additional crossreacting protein of molecular weight of 80K is also evident in the lacrimal gland. All these enzyme preparations, however, contain another immunoreactive protein of molecular weight of about 64K. While 73-80K molecular weight interacting proteins may represent different forms of peroxidase, presumably with varied carbohydrate moieties, 64K molecular weight protein may be a precursor of the peroxidase which after posttranslational modification such as heme conjugation and glycosylation leads to formation of native enzyme. Rat harderian gland, unlike bovine origin, does not contain any detectable peroxidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗