Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Peroxide-dependent enzymic oxidation of tyrosine to dopachrome and melanin was demonstrated in cell-free melanoma homogenates. Histochemical methods for distinguishing peroxidase activity from aerobic dopa (3,4-dihydroxyphenylalanine) oxidase activity are not reliable with cell-free preparations. Therefore the presence of peroxidase activity in such preparations precludes assay of cresolase activity of mammalian ;tyrosinase'.
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PMID:Peroxidatic oxidation of tyrosine to melanin in supernatant of crude mouse melanoma homogenates. 444 86

Isozymes of tobacco pith polyphenoloxidases (o-diphenol oxidase, EC 1.10.3.1) were separated electrophoretically from fresh pith of intact plants and from cultured pith sections. Extracts of fresh pith contained a poorly resolved complex of two to three anodic bands after starch gel electrophoresis at alkaline pH. This anodic complex was more active with chlorogenic acid than with 3,4-dihydroxyphenylalanine and was found in greater activity per gram fresh weight of tissue in younger internodes than in older ones. The longitudinal gradient of activity was thus the opposite of that found for the constitutive isozymes of peroxidase.A well defined cathodic band of polyphenoloxidase activity appeared after culture of pith in modified White's medium with shaking. This band, which was more active with 3,4-dihydroxyphenylalanine than with chlorogenic acid, could be detected after 1 to 2 days of incubation. Its appearance was enhanced by the addition of 10 mum indoleacetic acid; kinetin (1 mum tended to prevent this indoleacetic acid effect). Such hormonal control is opposite to that previously reported for the rapidly appearing new isozymes of peroxidase. The pattern of the major isozymes associated with polyphenoloxidase activities differs from that of peroxidase.
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PMID:Ontogeny and hormonal control of polyphenoloxidase isozymes in tobacco pith. 499 42

The activities of three enzymes, tyrosinase (monophenol oxidase, MPO), N-acetyltransferase (NAT), and tyrosine aminotransferase (TAT), were studied during eumelanotic encapsulation in host larvae of Drosophila melanogaster parasitized by the wasp, Leptopilina boulardi. At 24 h postinfection there was a tenfold increase in the MPO, whereas the activities of NAT and TAT were lower than those of nonparasitized controls. The data suggest that certain developmental processes are temporarily interrupted and alterations made in the metabolism of tyrosine to provide the metabolites necessary for a successful immune response. Two strains of D. melanogaster, R and Tyr-1, were parasitized and found to be immune reactive. The Tyr-1 strain is deficient in tyrosinase during the adult stage, but this mutation was found not to affect the immune capacity of the larvae. This is the first study to document concurrent alterations in the activities of various catecholamine-metabolizing enzymes during an immune response in an insect.
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PMID:Alterations in the activities of tyrosinase, N-acetyltransferase, and tyrosine aminotransferase in immune reactive larvae of Drosophila melanogaster. 809 20

During solid-state fermentation of wheat straw, a natural lignocellulosic substrate, the white rot fungus Pleurotus ostreatus produced an extracellular H2O2-requiring Remazol brilliant blue R (RBBR)-decolorizing enzymatic activity along with manganese peroxidase, manganese-independent peroxidase, and phenol oxidase activities. The presence of RBBR was not essential for the production of RBBR-decolorizing enzymatic activity by P. ostreatus, because this activity was also produced in the absence of RBBR. This RBBR-decolorizing enzymatic activity in crude enzyme preparations of 14- and 20-day-old cultures exhibited an apparent Km for RBBR of 31 and 52 microM, respectively. The RBBR-decolorizing enzyme activity was maximal in the pH range 3.5 to 4.0. This activity was independent of manganese, and veratryl alcohol had no influence on it. Manganese peroxidase of P. ostreatus did not decolorize RBBR. This H2O2-dependent RBBR-decolorizing enzymatic activity behaved like an oxygenase possessing a catalytic metal center, perhaps heme, because it was inhibited by Na2S2O5, NaCN, NaN3, and depletion of dissolved oxygen. Na2S2O5 brought an early end to the reaction without interfering with the initial reaction rate of RBBR oxygenase. The activity was also inhibited by cysteine. Concentrations of H2O2 higher than 154 microM were observed to be inhibitory as well. Decolorization of RBBR by P. ostreatus is an oxidative process.
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PMID:Involvement of an extracellular H2O2-dependent ligninolytic activity of the white rot fungus Pleurotus ostreatus in the decolorization of Remazol brilliant blue R. 852 4

Phenoloxidase (PO) activity in the albumen gland (AG) and egg masses (EM) of Biomphalaria glabrata was assessed using high-performance liquid chromatography combined with electrochemical detection and colorimetric techniques. Both AG and EM extracts catalyzed the hydroxylation of L-tyrosine (monophenol oxidase activity, MPO) and oxidation of L-dopa (diphenol oxidase activity, DPO). However, no PO activity was found in the ovotestis. Both MPO and DPO activities in AG and EM were significantly inhibited by 1-phenyl-2-thiourea and inactivated by boiling. Approximately 35% of MPO and 44% of DPO activities were detected in the soluble fraction of homogenized EM, in contrast to that of homogenized AG, which contained about 5% and 12%, respectively, of MPO and DPO activities. N-acetyl-dopamine, a diphenolic compound, enhanced the hydroxylation of tyrosine by the PO. The presence of both MPO and DPO activities also was confirmed by the accelerated accumulation of dopachrome during incubation of EM extracts with L-tyrosine in the absence of ascorbate. Temperature and pH optima for this enzyme were 30 degrees C and 7.5, respectively. The potential roles of PO in egg formation in B glabrata are discussed.
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PMID:Phenoloxidase activity in the reproductive system and egg masses of the pulmonate gastropod, Biomphalaria glabrata. 884 May 12

Peroxidase activity is detectable in Aedes aegypti ovaries, containing developing eggs, at 24 h following blood feeding, and peak peroxidase activity is reached at 36-48 h after the blood-meal. Peroxidase is associated with the chorion layer in mature eggs and the majority of the enzyme is released from the chorion layer by treating the isolated chorion fraction with SDS/urea. Analysis of the SDS/urea solubilized chorion proteins using SDS-PAGE with tropolone/H2O2 or dopa staining verified the presence of both peroxidase and phenol oxidase in the released chorion proteins. The molecular weight of chorion peroxidase is about 61,000 Da as determined by SDS-PAGE analysis. Incubation of the solubilized chorion proteins with tyrosine and H2O2 produces dityrosine, and hyrolysis of hardened egg chorion results in the detection of dityrosine and trityrosine in the chorion hydrolysate. Data suggest that chorion peroxidase is involved in the hardening of the mosquito egg chorion by catalyzing the formation of ditryrosine through tyrosine residues on structural proteins. The overall hardening of the A. aegypti egg chorion includes both peroxidase-mediated chorion protein crosslinking through dityrosine formation and phenol oxidase-catalyzed chorion melanization.
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PMID:Involvement of peroxidase in chorion hardening in Aedes aegypti. 890 May 99

Crude aqueous extracts from the peripheral rot zone of cocoyam tubers infected by Sclerotium rolfsii sacc were shown to be inhibitory to dialysed in vivo polygalacturonase (PG) of the pathogen. The PG inhibitory action, phenol oxidase and peroxidase activities were higher in cocoyam tubers of the Xanthosoma sagittifolium varieties than in those of the Coolocasia esculenta varieties. The levels of phenol oxidase, peroxidase and PG inhibitory activities also decreased as the postharvest age of the tubers increased.
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PMID:Changes in phenol oxidase and peroxidase levels in cocoyam tubers of different postharvest ages infected by Sclerotium rolfsii sacc. 897 42

The cytochemical localization of the phenol oxidases, laccase and peroxidase, has been studied in pro-lignifying and lignifying Coleus blumei stem sections using 4-methoxy-alpha-naphthol as substrate. The results illustrated that, for short incubation times, both pro-lignifying and lignifying Coleus sections showed H2O2-dependent phenol oxidase (peroxidase-like) activity in epidermal and vascular tissues, while no detectable H2O2-independent phenol oxidase (laccase-like) activity was found in Coleus tissues. For long incubation times, H2O2-independent phenol-oxidases can also be detected in these tissues, however, this is probably due to the partial capability of intercellular washing fluid Coleus peroxidase to oxidize 4-methoxy-alpha-naphthol in the absence of exogenously added H2O2. This illustrates not only the importance of the substrate used, but also the importance of the incubation time, in the cytochemical localization of phenol oxidizing enzymes.
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PMID:Cytochemical localization of phenol-oxidizing enzymes in lignifying Coleus blumei stems. 917 41

The separation of haemocytes from the mussel Mytilus edulis was carried out on continuous Percoll gradients. The haemocytes separated into three distinct layers, the first comprised 97% basophilic cells, the third comprised 84% eosinophilic cells and the middle layer was a mixture of eosinophilic and basophilic cells. Enzyme cytochemistry demonstrated arylsulphatase, phenol oxidase and peroxidase associated with the haemocytes from the third layer. Lectin-binding studies showed differential binding of lectins to the separated cells. The ultrastructural morphology demonstrated that the first layer of cells was composed predominantly of small agranular cells with a high nucleus to cytoplasm ratio. The second layer comprised a mixture of cells with the majority being granular cells with small granules. The third layer was almost exclusively composed of granular cells with small and large granules. Assays to assess the function of the different cells demonstrated that respiratory burst activity, measured as the reduction of cytochrome-c, was carried out almost entirely by the eosinophilic haemocytes. Similarly, levels of phagocytosis, measured as uptake of Escherichia coli, were much higher in the eosinophilic haemocytes. Of the potential mitogenic factors investigated, concanavalin A and pokeweed mitogen showed some evidence of inducing haemocyte proliferation.
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PMID:The separation and characterisation of haemocytes from the mussel Mytilus edulis. 923 32

Detergent solubilized extracts of the cochleae of adult gerbils (Meriones unguiculatus) contain a tyrosine hydroxylase activity measurable by the radiometric method of Pomerantz. This activity is not related to Fenton-type reactions, since it is not inhibited by free radical scavengers and is heat and protease sensitive. It does not appear to be related to a peroxidase (EC 1.11.1.7) since it is neither dependent on H2O2, nor inhibited by catalase (EC 1.11.1.6). The involvement of a tyrosine hydroxylase (EC 1.14.16.2) related to catecholamine synthesis is also unlikely, since the activity is highly sensitive to 2-mercaptoethanol and is not increased by addition of tetrahydrobiopterin. The activity in crude inner ear extracts displayed an unusual maturation behaviour, with a slow activation upon aging at 4 degrees C. Fully active enzyme displayed Michaelis-Menten kinetics, with a Km for L-tyrosine of 47 microM. Cochlear tyrosine hydroxylase, but not melanoma tyrosinase (EC 1.14.18.1), was inhibited by o-phenanthroline, and was not dependent on L-DOPA as cofactor for full enzymatic activity. Crude extracts were also able to catalyze L-DOPA oxidation and melanin formation from either L-tyrosine or L-DOPA. The tyrosine hydroxylase, DOPA oxidase and melanin formation activities most probably resided in the same molecule, as suggested by inhibition studies. A tyrosine hydroxylase and melanin formation activity with identical properties was found in primary cultures of stria vascularis melanocytes. Immunochemical evidence confirmed the absence of either the tyrosinase encoded for by the albino locus, or the tyrosinase isoenzyme TRP1, encoded for by the brown locus. Conversely, an immunorreactive band of molecular weight 70 kDa was specifically recognized by a tyrosinase polyclonal antiserum in Western blot experiments. These results prove that melanogenesis in the cochlea, and likely in other extracutaneous locations such as the brain, is catalyzed by enzymatic systems different from, but related to tyrosinase.
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PMID:Melanin formation in the inner ear is catalyzed by a new tyrosine hydroxylase kinetically and structurally different from tyrosinase. 927 Dec 51


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