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

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Query: EC:1.6.5.4 (SOR)
720 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The involvement of the ascorbate (AsA) system in the response of pumpkin (Cucurbita pepo L.) roots to aluminium stress was studied. The treatment of 5-day-old pumpkin seedlings with 50 microM aluminium sulphate resulted in approximately 60% inhibition of root growth within 48-60 h of treatment, while aluminium accumulated in the roots reaching a maximum within 48h. During the same period, the hydrogen peroxide content of the roots was strongly enhanced. The increased level of hydrogen peroxide was matched by both increased ascorbate peroxidase (APX) (EC 1.11.1.11) activity and ascorbate free radical reductase (AFRR) (EC 1.1.5.4) activity, while dehydroascorbate reductase (DHAR) (EC 1.8.5.1) and glutathione reductase (GR) (EC 1.6.4.2) did not change. The levels of AsA in the roots were also increased by the Al treatment. It was concluded that an oxidative burst is probably involved in the toxicity of Al in pumpkin roots and that plants react to the enhanced production of reactive oxygen species by expressing higher levels of scavenging systems such as the AsA-APX system.
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PMID:Changes in the ascorbate system in the response of pumpkin (Cucurbita pepo L.) roots to aluminium stress. 1594 Aug 70

The response of the enzymes and metabolites of the ascorbate-glutathione pathway to oxidative stress caused by re-aeration following hypoxia was studied in roots of hydroponically grown lupine (Lupinus luteus L. cv. Juno) seedlings. Lupine roots were deprived of oxygen by subjecting them to hypoxia for 48 and 72 h and then re-aerated for up to 4 h. An increased content of total ascorbate was observed in lupine roots immediately after hypoxia, whereas total glutathione level decreased. However, a significant increase in the reduced forms of both metabolites was found directly after hypoxia. Re-admission of oxygen caused the decrease of the ratios of reduced to oxidized forms of ascorbate and glutathione, indicating oxidative stress. While monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activity remained unaltered during re-aeration the increase in activities of ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) was observed 30 min after transfer from hypoxic condition. Dehydroascorbate reductase (DHAR, EC 1.8.5.1) activity approached the control level during a whole re-aeration period. Native gel electrophoresis combined with specific activity staining revealed seven isoforms of APX, five isoforms of GR and three different proteins with DHA reductase activity in roots extracts. However, immediately after hypoxic treatment APX-5 isoform and GR-1 isoform were not observed in roots. This experimental system was also used to investigate superoxide anion level in roots utilizing the superoxide anion-specific indicator dihydroethidium (DHE). Intense DHE-derived fluorescence was found in re-aerated root tips as compared to control roots, indicating that re-aeration induced superoxide anion production in hypoxically pretreated roots.
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PMID:Response of the ascorbate-glutathione cycle to re-aeration following hypoxia in lupine roots. 1597 6

The utility of antioxidant enzymes, viz glutathione-S-transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), as biomarkers of heavy metal pollution in water was investigated using the Allium cepa (onion) system. These antioxidant enzymes were assayed in onion bulbs exposed to certain heavy metals taken separately, the test metals taken in combination as well as the industrial wastewater especially found to contain these metals. GST exhibited significantly enhanced activity upon treatment with individual heavy metals. However, GR, SOD and CAT did not show such a pronounced increase in activities. At higher heavy metal concentrations, GR, SOD and CAT showed a steep decline while GST activity still showed a rise. Moreover, APX, GPX and MDHAR also exhibited remarkable induction with increase in the concentration of individual heavy metals. However, there was no significant change in DHAR activity with respect to the controls. Metabolites like ascorbate (ASC) and glutathione (GSH) exhibited significant decline with increase in the concentration of individual heavy metals while the level of H(2)O(2) continued to display the rise up to a heavy metal concentration of 100 microM, after which it showed a gradual decline. A. cepa bulbs treated with wastewater sample showed enzyme activity profiles similar to that shown with heavy metals, thereby suggesting the presence of heavy metals in the test wastewater. Atomic absorption spectrophotometry also detected large amounts of Cd, Cr, Cu, Hg, Pb and Zn in the test water sample. The metal mixture, containing the amounts of heavy metals equivalent to those found in the wastewater, resulted in steep declines in GR, SOD and CAT activities in A. cepa while GST showed a rise. However, when this metal mixture was diluted to 2000-fold, GR, SOD and CAT also showed enhanced activities compared with the controls. Contrary to the above finding, APX, GPX and MDHAR exhibited the rise in activities in A. cepa exposed to the metal mixture at all dilutions. In the presence of cycloheximide, all the enzymes returned to the levels of untreated controls while chloramphenicol did not have any effect on the test enzymes, thereby suggesting de novo protein synthesis of the test antioxidant enzymes in the cytosolic compartment of the cell as a result of exposure to the heavy metals.
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PMID:Certain antioxidant enzymes of Allium cepa as biomarkers for the detection of toxic heavy metals in wastewater. 1599 99

The H2O2 byproduct of fatty acid catabolism in plant peroxisomes is removed in part by a membrane-associated antioxidant system that involves both an ascorbate peroxidase and a monodehydroascorbate reductase (MDAR). Despite descriptions of 32-kDa MDAR polypeptides in pea and castor peroxisomal membranes and cDNA sequences for several 'cytosolic' MDARs, the genetic and protein factors responsible for peroxisomal MDAR function have yet to be elucidated. Of the six MDAR polypeptides in the Arabidopsis proteome, named AtMDAR1 to AtMDAR6 in this study, 47-kDa AtMDAR1 and 54-kDa AtMDAR4 possess amino acid sequences that resemble matrix (PTS1) and membrane peroxisomal targeting signals, respectively. Epitope-tagged versions of these two MDARs and a pea 47-kDa MDAR (PsMDAR) sorted in vivo directly from the cytosol to peroxisomes in Arabidopsis and BY-2 suspension cells, whereas AtMDAR2 and AtMDAR3 accumulated in the cytosol. The PTS1-dependent sorting of AtMDAR1 and PsMDAR to peroxisomes was incomplete (inefficient?), but was improved for PsMDAR after changing its PTS1 sequence from -SKI to the canonical tripeptide -SKL. A C-terminal transmembrane domain and basic cluster of AtMDAR4 were necessary and sufficient for targeting directly to peroxisomes. MDAR activity in isolated Arabidopsis peroxisomes was distributed among both water-soluble matrix and KCl-insoluble membrane subfractions that contained respectively 47- and 54-kDa MDAR polypeptides. Notably, a 32-kDa MDAR was not identified. Combined with membrane association and topological orientation findings, these results indicate that ascorbate recycling in Arabidopsis (and probably other plant) peroxisomes is coordinated through functionally redundant MDARs that reside in the membrane and the matrix of the organelle.
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PMID:Arabidopsis peroxisomes possess functionally redundant membrane and matrix isoforms of monodehydroascorbate reductase. 1614 28

The regulation of the antioxidant defence system by ultraviolet-B (UV-B) was determined in a marine macroalga Ulva fasciata Delile exposed to low (0.5, 1 W m(-2)), medium (2.5, 5 W m(-2)), and high (10, 20 W m(-2)) UV-B irradiance. UV-B > or =2.5 W m(-2) increased H2O2 contents that are positively correlated with lipid peroxidation and total peroxide contents. Inhibition of the UV-B-induced H2O2 increase by a specific O2.- scavenger, 1,2-dihydroxy-benzene-3,5-disulphonic acid, shows that O2.- is the primary source of H2O2. Superoxide dismutase activity was increased by UV-B with a peak at 2.5 W m(-2), which did not match the H2O2 pattern. Alleviation of UV-B-induced oxidative damage by a H2O2 scavenger, dimethylthiourea, and a free radical scavenger, sodium benzoate, which inhibited UV-B-induced H2O2 accumulation, suggests that oxidative damage caused by UV-B > or = 2.5 W m(-2) is ascribed to accumulated H2O2. However, a decrease in growth rate and TTC reduction ability only at high UV-B doses indicates that the defence and repairing systems operate at low and medium UV-B doses. H2O2 not only can be excreted but can also be detoxified via the ascorbate-glutathione cycle. Increases in catalase, peroxidase, ascorbate peroxidase, and glutathione reductase activities and ascorbate (AsA) and glutathione pools, as well as AsA regeneration ability, function to keep the balance of cellular H2O2 under low UV-B doses. Dehydroascorbate reductase and monodehydroascorbate reductase are responsible for AsA regeneration under low and medium UV-B radiation, respectively. The appearance of oxidative damage in medium and high UV-B flux is attributable to a lower induction of the ascorbate-glutathione cycle as an antioxidant defence system. Overall, the availability of antioxidants and the induction of antioxidant enzyme activities for detoxifying reactive oxygen species (ROS) are regulated in U. fasciata against UV-B-induced oxidative stress, and experiments using ROS scavengers demonstrate that the antioxidant defence system is modulated by O2.- or H2O2.
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PMID:Ultraviolet-B-induced oxidative stress and responses of the ascorbate-glutathione cycle in a marine macroalga Ulva fasciata. 1615 54

In the course of nitric oxide (NO) scavenging, hemoglobin (Hb) turnover is linked to antioxidant metabolism and affects the cellular redox level. The influence of Hb presence on the ascorbate-glutathione cycle enzymes and the levels of H(2)O(2) and ascorbate was investigated in alfalfa root cultures transformed to over-express (Hb+) or down-regulate (Hb-) class-1 Hb. Hb+ lines had substantially increased ascorbate levels as well as elevated monodehydroascorbate reductase and ascorbate peroxidase activities. Hb- lines showed significant increases in dehydroascorbate reductase and glutathione reductase activities. The observed changes in ascorbate and ascorbate-glutathione cycle enzymes were pronounced both at high (40 kPa) and low (3 kPa) O(2) pressures. Hb- lines had significantly reduced levels of the NO- and H(2)O(2)-sensitive enzyme, aconitase, as compared to Hb+ lines. This reduced activity was likely due the higher levels of NO in Hb- lines, as treatment of plant extracts with the NO-donor DEANO also affected aconitase activity. The H(2)O(2) levels were not significantly different amongst the lines and showed no variation with change in oxygen partial pressure. In conclusion, the expression of class-1 Hb improves the antioxidant status through increased ascorbate levels and increased activity of enzymes involved in H(2)O(2) removal.
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PMID:Class-1 hemoglobin and antioxidant metabolism in alfalfa roots. 1628 78

The effects of methyl jasmonate (MJ) and salicylic acid (SA) on changes of the activities of major antioxidant enzymes, superoxide anion accumulation (O2-), ascorbate, total glutathione (TG), malondialdehyde (MDA) content and ginsenoside accumulation were investigated in ginseng roots (Panax ginseng L.) in 4 l (working volume) air lift bioreactors. Single treatment of 200 microM MJ and SA to P. ginseng roots enhanced ginsenoside accumulation compared to the control and harvested 3, 5, 7 and 9 days after treatment. MJ and SA treatment induced an oxidative stress in P. ginseng roots, as shown by an increase in lipid peroxidation due to rise in O2- accumulation. Activity of superoxide dismutase (SOD) was inhibited in MJ-treated roots, while the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), SOD, guaiacol peroxidase (G-POD), glutathione peroxidase (GPx) and glutathione reductase (GR) were induced in SA-treated roots. A strong decrease in the activity of catalase (CAT) was obtained in both MJ- and SA-treated roots. Activities of ascorbate peroxidase (APX) and glutathione S transferase (GST) were higher in MJ than SA while the contents of reduced ascorbate (ASC), redox state (ASC/(ASC+DHA)) and TG were higher in SA- than MJ-treated roots while oxidized ascorbate (DHA) decreased in both cases. The result of these analyses suggests that roots are better protected against the O2- stress, thus mitigating MJ and SA stress. The information obtained in this work is useful for efficient large-scale production of ginsenoside by plant-root cultures.
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PMID:Methyl jasmonate and salicylic acid elicitation induces ginsenosides accumulation, enzymatic and non-enzymatic antioxidant in suspension culture Panax ginseng roots in bioreactors. 1646 59

Hydrogen peroxide (H(2)O(2)) scavenging systems of spruce (Picea abies) needles were investigated in both extracts obtained from the extracellular space and extracts of total needles. As assessed by the lack of activity of symplastic marker enzymes, the extracellular washing fluid was free from intracellular contaminations. In the extracellular washing fluid ascorbate, glutathione, cysteine, and high specific activities of guaiacol peroxidases were observed. Guaiacol peroxidases in the extracellular washing fluid and needle homogenates had the same catalytic properties, i.e. temperature optimum at 50 degrees C, pH optimum in the range of pH 5 to 6 and low affinity for guaiacol (apparent K(m) = 40 millimolar) and H(2)O(2) (apparent K(m) = 1-3 millimolar). Needle homogenates contained ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase, and catalase, but not glutathione peroxidase activity. None of these activities was detected in the extracellular washing fluid. Ascorbate and glutathione related enzymes were freeze sensitive; ascorbate peroxidase was labile in the absence of ascorbate. The significance of extracellular antioxidants for the detoxification of injurious oxygen species is discussed.
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PMID:Composition and Properties of Hydrogen Peroxide Decomposing Systems in Extracellular and Total Extracts from Needles of Norway Spruce (Picea abies L., Karst.). 1666 3

Large changes occur in the ascorbate system during the development of Vicia faba seed and these appear closely related to what are generally considered to be the three stages of embryogenesis. During the first stage, characterized by embryonic cells with high mitotic activity, the ascorbic acid/dehydroascorbic acid ratio is about 7, whereas in the following stage, characterized by rapid cell elongation (stage 2), it is lower than 1. The different ascorbic/dehydroascorbic ratio may be correlated with the level of ascorbate free radical reductase activity, which is high in stage 1 and lower in stage 2. Ascorbate peroxidase activity is high and remains constant throughout stages 1 and 2, but it decreases when the water content of the seed begins to decline (stage 3). In the dry seed, the enzyme disappears together with ascorbic acid. Ascorbate peroxidase activity is observed to be 10 times higher than that of catalase, suggesting that ascorbate peroxidase, rather than catalase, is utilized in scavenging the H(2)O(2) produced in the cell metabolism. There is no ascorbate oxidase in the seed of V. faba. V. faba seeds acquire the capability to synthesize ascorbic acid only after 30 days from anthesis, i.e. shortly before the onset of seed desiccation. This suggests that (a) the young seed is furnished with ascorbic acid by the parent plant throughout the period of intense growth, and (b) it is necessary for the seed to be endowed with the ascorbic acid biosynthetic system before entering the resting state so that the seed can promptly synthesize the ascorbic acid needed to reestablish metabolic activity when germination starts.
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PMID:Changes in the Ascorbate System during Seed Development of Vicia faba L. 1666 55

In this work the influence of the nodulation of pea (Pisum sativum L.) plants on the oxidative metabolism of different leaf organelles from young and senescent plants was studied. Chloroplasts, mitochondria, and peroxisomes were purified from leaves of nitrate-fed and Rhizobium leguminosarum-nodulated pea plants at two developmental stages (young and senescent plants). In these cell organelles, the activity of the ascorbate-glutathione cycle enzymes ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), and the ascorbate and glutathione contents were determined. In addition, the total superoxide dismutase (SOD) activity, the pattern of mitochondrial and peroxisomal NADPH-generating dehydrogenases, some of the peroxisomal photorespiratory enzymes, the glyoxylate cycle and oxidative metabolism enzymes were also analysed in these organelles. Results obtained on the metabolism of cell organelles indicate that nodulation with Rhizobium accelerates senescence in pea leaves. A considerable decrease of the ascorbate content of chloroplasts, mitochondria, and peroxisomes was found, and in these conditions a metabolic conversion of leaf peroxisomes into glyoxysomes, characteristic of leaf senescence, took place.
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PMID:Antioxidative enzymes from chloroplasts, mitochondria, and peroxisomes during leaf senescence of nodulated pea plants. 1669 15


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