Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Desialylated glycoproteins were covalently linked to two cytochemically detectable enzymes, horseradish peroxidase or tyrosinase, and injected intravenously in amounts of approximately 0.5 per cent of total plasma glycoproteins into rats. Comparative studies of the rates of disappearance and distribution of free enzyme and conjugates established that recognition of the conjugates by the plasma membranes of hepatocytes was due to the exposure of the terminal galactose residue of the desialylated glycoproteins. At 1 minute after injection, reaction products of the enzyme markers were seen in coated pits and vesicles, elongated pinocytic channels and pleomorphic vesicles, at or close to the sinusoidal surface of hepatocytes. Vesicles containing reaction products were also observed along the lateral surfaces of hepatocytes. By 10 minutes, reaction products were seen in residual bodies near the biliary poles of hepatocytes. These studies confirm the existence of hepatocellular channels previously seen only with large excess of hemoglobin or following partial hepatectomy. They also indicate that the specific receptor for asialoglycoproteins is not restricted to the sinusoidal surfaces of hepatocytes and that transport to the catabolic sites proceeds via cytoplasmic channels and vesicles.
...
PMID:Endocytosis of asialoglycoprotein-enzyme conjugates by hepatocytes. 677 3

The mitochondrial fraction of diethylstilbestrol-treated rat uteri, known to contain an estrogen-induced peroxidase, was able to catalyze the release of 3H2O from either [2-3H]- or [4-3H]estradiol. Hydrogen peroxide added to this system increased the yield of 3H2O but had no effect on mitochondrial preparations from ovariectomized rat uteri having only very low peroxidase activity. The reaction was inhibited by catalase and also occurred with lactoperoxidase in the presence of H2O2 but 2-hydroxyestradiol was not detected in any of these experiments. Under similar conditions, tyrosinase catalyzed the formation of the catechol estrogen with loss of 3H from [2-3H]- or [2,4,6,7-3H]- but not [4-3H]- or [6,7-3H]estradiol. It is proposed that the formation of 3H2O from 3H-labeled estradiol in the estrogen-treated rat uterus may occur by a peroxidative mechanism which does not necessarily result in hydroxylation of the steroid.
...
PMID:Formation of 3H2O from [2-3H]- and [4-3H] estradiol by rat uteri in vitro: possible role of peroxidase. 739 59

Mutations in the tyrosinase gene are often associated with a misrouting of retinal ganglion cell axons at the optic chiasm. In albinos, tyrosinase activity is lost and some ganglion cell axons that would normally project into the ipsilateral optic tract instead cross midline and project into the contralateral tract. The developmental mechanisms that cause this modification in neuronal connectivity are unknown. In this study, we screened six diverse strains of albino mice (strains 129, A, AKR, BALB/c, C57BL/6-c/c, and CD-1) to discover genetically determined variations and possible gene loci that might affect the severity of the albino decussation abnormality. Ganglion cells were retrogradely labeled with horseradish peroxidase, and the ipsilaterally and contralaterally projecting cells were counted. The average number of ipsilaterally projecting ganglion cells in the six albino strains varies from 1,000 to 1,300. Despite this variation, 1.8-1.9% of the total population projects ipsilaterally in each strain. In comparison, 2.8% project ipsilaterally in the pigmented strain, C57BL/6(-)+/+. However, the percentage of displaced, ipsilaterally projecting cells varies substantially among albino strains--from a low of 4% in strain CD-1 to a high of nearly 10% in C57BL/6-c/c. We conclude that even with large differences in genetic background and in absolute numbers of ganglion cells, there is no appreciable variation in the magnitude of decussation error among albino mice. The consistent effect of null alleles at tyrosinase suggests a comparably tight linkage between the biochemical activity of this enzyme and the mechanisms that control decussation phenotype.
...
PMID:Genetic control of retinal projections in inbred strains of albino mice. 760 32

At physiological pH values, oxidation of the neurotransmitter dopamine (DA) by the peroxidase/H2O2 system leads to, besides dopaminochrome and 5,6-dihydroxyindole resulting from oxidative cyclization of dopaminequinone (DQ), significant amounts of the neurotoxin 6-hydroxydopamine (6-OHDA) in the oxidized quinonoid form (topaminequinone, TQ). Formation of TQ was shown to depend critically on the presence of hydrogen peroxide in the reaction medium and was not observed when DA oxidation was carried out using the tyrosinase/O2 system or chemical agents such as periodate or ferricyanide. These and other data suggest that, under the conditions adopted, nucleophilic attack of the hydrogen peroxide anion on DQ leading to TQ significantly competes with the intramolecular cyclization path. In line with this mechanism, the reaction course was not affected by the presence of hydroxyl radical scavengers. Peroxidase/H2O2 oxidation of the model N-acetyldopamine (1) gave, as expected, the 2-hydroxy-1,4-benzoquinone 3 in yields up to 55%, depending on the catecholamine/H2O2 mole ratio. Likewise, reaction of 4-methyl-1,2-benzoquinone (4) with hydrogen peroxide afforded 2-hydroxy-5-methyl-1,4-benzoquinone (5) in good yields. Collectively, these results would point to the possibility that intraneuronal formation of 6-OHDA is associated with an increased production of hydrogen peroxide under oxidative stress conditions.
...
PMID:Generation of the neurotoxin 6-hydroxydopamine by peroxidase/H2O2 oxidation of dopamine. 769 8

The endogenous pentapeptides, met-enkephalin and leuenkephalin, similar to their parent structures, beta-endorphin or dynorphin, bind to opioid receptors of the nociceptive system thus provoking analgesic responses. Peroxidases and phenolases (tyrosinase, catecholase) were shown to dimerize these pentapeptides thus possibly modulating their activity and/or lifetime. Extracts from plants from the order of the Papaverales contain isoquinoline alkaloids. Since the benzoisoquinolines are known to possess sedative-hypnotic activities, the potential effects of extracts from two species from this plant group, Eschscholtzia californica (Papaveraceae) and tyrosinase-catalyzed dimerization and/or oxidation of met-enkephalin were investigated. The results of the study show that the peroxidase-catalyzed dimerization via the tyr-residues is especially inhibited by the C. cava extract. The tyrosinase-catalyzed reaction yields five different products A-E, according to their HPLC-retention times. Consisting of the 4:1 (v/v) combination of the extracts from E. californica and C. cava, Phytonoxon N (abbreviated as PN) stimulates the formation of minor products A, B and E, whereas the formation of the major products C and D is inhibited. Only products C and D exhibit properties similar to the peroxidase-derived dimer. Product A is likely to be identical to DOPA-enkephalin.
...
PMID:Effects of ethanolic extracts from Eschscholtzia californica and Corydalis cava on dimerization and oxidation of enkephalins. 771 Apr 33

Phenolic compounds can act as radical scavengers due to their ability to donate a mobile hydrogen to peroxyl radicals producing a phenoxyl radical if the phenoxyl radical formed in the radical scavenging reaction efficiently interacts with vitally important biomolecules, then this interaction may result in cytotoxic effects rather than in antioxidant protection. In the present work we have chosen two model compounds--a phenolic antitumor drug, VP-16, known to be highly cytotoxic, and a homolog of vitamin E, 2,2,5,7,8-pentamethyl-6-hydroxychromane (PMC)--as typical representatives of phenoxyl radicals to study interactions of their phenoxyl radicals with intracellular thiols. Using a water-soluble source of peroxyl radicals, the azo-initiator 2,2'-azobis(2-aminodinopropane) (AAPH), we found that both PMC and VP-16 are very efficient scavengers of peroxyl radicals as evidenced by their ability to inhibit AAPH-induced chemiluminescence of luminol and oxidation of PnA incorporated into DOPC liposomes. Both PMC and VP-16 were also able to protect against AAPH-induced oxidative degradation of DNA in nuclei from human leukemic K562 cells. In contrast, there was a dramatic difference in the ability of VP-16 and PMC to protect GSH against AAPH-induced oxidation: while PMC inhibited AAPH-induced oxidation of GSH in a concentration-dependent manner, VP-16 did not protect GSH against oxidation. We hypothesized that this was due to different reactivities of the phenoxyl radicals formed by AAPH-derived peroxyl radicals from VP-16 and PMC toward GSH. To substantiate this hypothesis, we compared interactions of the phenoxyl radicals generated from VP-16 and PMC with intracellular thiols in K562 cell homogenates. While the PMC phenoxyl radicals were only slightly affected by thiols, the VP-16 phenoxyl radicals were reduced by thiols. This is evidenced by (i) a significant inhibition of the tyrosinase-induced VP-16 consumption upon addition of K562 cell homogenates, (ii) a depletion of endogenous thiols in K562 cell homogenates induced by VP-16+tyrosinase, (iii) a transient disappearance of the VP-16 phenoxyl radical signal from the ESR spectra and its reappearance after depletion of endogenous thiols, and (iv) elimination of the lag period for the appearance of the VP-16 phenoxyl radical ESR signal subsequent to depletion of thiols by mersalyl acid. To evaluate the contribution of GSH and protein thiols to reduction of the VP-GSH-peroxidase + cumeme hydroperoxide to specifically deplete endogenous GSH.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Phenoxyl radicals of etoposide (VP-16) can directly oxidize intracellular thiols: protective versus damaging effects of phenolic antioxidants. 771 69

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.
...
PMID:Alterations in the activities of tyrosinase, N-acetyltransferase, and tyrosine aminotransferase in immune reactive larvae of Drosophila melanogaster. 809 20

Explants and callus of C. pendulus produced intense brown substances in the medium which caused necrosis. Various anti-oxidants (ascorbic acid, cysteine and dithiothreitol) and adsorbents (activated charcoal and polyvinyl pyrrolidone) were used in different concentrations to prevent browning of the tissues. These in MS medium affected differently the growth, colour and texture of the tissues. It was concluded that both peroxidase and phenolase were involved in the browning. Increased peroxidase activity and decreased phenolase activity were probably due to more peroxidative oxidation of phenols and unavailability of substrate for phenolase activity. This resulted in faster growth of tissues, which further reduced the phenolase activity.
...
PMID:Effect of anti-oxidants and adsorbents on tissue browning associated metabolism in Cocculus pendulus callus cultures. 827 Feb 86

In the pigment cells of the white mutant of Drosophila melanogaster, as described earlier, two types of abnormal granules are found by conventional electron microscopy. However, both types of abnormal granules, in addition to those in pigment cell invaginations, are also present in the cytoplasm of the photoreceptor cells. Three enzymes (acid phosphatase, peroxidase, and tyrosinase) are localized within the eyes of wild type and white mutant Drosophila melanogaster by electron microscopy. Peroxidase activity is present in lamellar bodies close to the rhabdomeral microvilli of both fly types. However the organelles containing peroxidase activity are 6-fold more frequent in the wild type than in the mutant. Acid phosphatase is present in lamellar bodies between and at the bases of the rhabdomeral microvilli of the wild type, as well as in ommochrome granules of the photoreceptor cells. In the white mutant, however, acid phosphatase was located in electron lucent vacuoles in the cytoplasm of the receptor cells. These acid phosphatase-positive vacuoles also contained both types of abnormal granules. The latter result indicates that abnormal granules in the receptor cells originate from lysosomal degradation and that targeting of lysosomal enzymes is altered in the white mutant. Due to the tyrosinase activity in the hemolymph of flies, the extracellular spaces are electron dense after DOPA incubation. Since some abnormal granules within the photoreceptor cells are not surrounded by an extracellular space, they can be assumed to originate within the photoreceptor cells.
...
PMID:Atypical granules in the eyes of the white mutant of Drosophila melanogaster are lysosome-related organelles. 839 98

The enzyme activity of tyrosinase, catalase, and peroxidase and the number of metal ions in melanogenic subcellular compartments in pigment cells were measured. Coated vesicles were richest in tyrosinase and catalase, whereas premelanosomes had the highest amount of peroxidase. Among metals ions examined, copper, zinc, and iron were more concentrated in pre-melanosomes than in coated vesicles. A quantitative analysis revealed that peroxidase served to enhance eumelanin polymer formation from monomers in the presence of hydrogen peroxide and metal ions, especially copper ions, which had the greatest enhancing effect on the conversion of monomers to polymers.
...
PMID:Non-melanosomal regulatory factors in melanogenesis. 844 Sep 3


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---