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:1.10.3.3 (ascorbate oxidase)
778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Real-time monitoring of L-glutamate release from various neuronal regions of mouse hippocampal slices under ischemia (a glucose-free hypoxia condition) is described. A glass capillary microelectrode with a tip size of approximately 10 microm containing a very small volume ( approximately 2 microL) of a solution of glutamate oxidase (GluOx) and ascorbate oxidase was used. First, the amperometric response behavior of the electrode at 0 V versus Ag/AgCl was characterized with a standard glutamate solution in terms of continuous measurements, effect of oxygen, viscosity of solution and concentration dependence. The electrode was applied to the real-time monitoring of L-glutamate released from different neuronal regions of acute hippocampal slices submerged in a hypoxia solution. The time-resolved amounts of L-glutamate released at various neuronal regions (CA1, CA3 and DG) of mouse hippocampal slices were quantified and compared with the reported L-glutamate fluxes using difference-image analysis during ischemia.
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PMID:Real-time monitoring of L-glutamate release from mouse brain slices under ischemia with a glass capillary-based enzyme electrode. 1615 99

D-Serine selectively causes necrosis of S(3) segments of proximal tubules in rats. This leads to aminoaciduria and glucosuria. Coinjection of the nonmetabolizable amino acid alpha-aminoisobutyric acid (AIB) prevents the tubulopathy. D-serine is selectively reabsorbed in S(3), thereby gaining access to peroxisomal D-amino acid oxidase (D-AAO). D-AAO-mediated metabolism produces reactive oxygen species. We determined the fractional excretion of amino acids and glucose in rats after intraperitoneal injection of d-serine alone or together with reduced glutathione (GSH) or AIB. Both compounds prevented the hyperaminoaciduria. We measured GSH concentrations in renal tissue before (control) and after D-serine injection and found that GSH levels decreased to approximately 30% of control. This decrease was prevented when equimolar GSH was coinjected with D-serine. To find out why AIB protected the tubule from D-serine toxicity, we microinfused D-[(14)C]serine or [(14)C]AIB (0.36 mmol/l) together with [(3)H]inulin in late proximal tubules in vivo and measured the radioactivity in the final urine. Fractional reabsorption of D-[(14)C]serine and [(14)C]AIB amounted to 55 and 70%, respectively, and 80 mmol/l of AIB or D-serine mutually prevented reabsorption to a great extent. D-AAO activity measured in vitro (using D-serine as substrate) was not influenced by a 10-fold higher AIB concentration. We conclude from these results that 1) D-AAO-mediated d-serine metabolism lowers renal GSH concentrations and thereby provokes tubular damage because reduction of reactive oxygen species by GSH is diminished and 2) AIB prevents d-serine-induced tubulopathy by inhibition of D-serine uptake in S(3) segments rather than by interfering with intracellular D-AAO-mediated D-serine metabolism.
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PMID:Why is D-serine nephrotoxic and alpha-aminoisobutyric acid protective? 1742 29

An alternative approach to production of amperometric microbiosensors, which combines electrochemical electrometallization and electropolymerisation of phenylene diamine film with covalent binding enzymes, is presented. In this respect, for a sensitive detection of hydrogen peroxide (HP) at +0.4V versus Ag/AgCl (detection limit of 0.5 microM, s/n=3), carbon fiber microelectrodes (30 microm in diameter and 500 microm long) were covered with ruthenium. To obtain a highly selective detection of HP, in the presence of different interfering compounds (ascorbic acid, uric acid, etc.), an additive semi-permeable polymer film was formed on the top of the ruthenium layer by electropolymerisation of m-phenylene diamine (m-PD). The enzymatic selective layers were formed by covalent cross-linking the enzymes (glucose oxidase, lactate oxidase or glutamate oxidase) with BSA by glutaraldehyde in the presence of ascorbate oxidase. An additional polymeric layer based on polyurethane and Nafion was deposited on the top of the enzymatic membrane (glucose oxidase, lactate oxidase, or glutamate oxidase) in order to extend the dynamic range of biosensors up to 4mM for glucose (R=0.997; Y[nA]=-0.22+9.68x[glucose, mM]), 1.75mM for lactate (R=0.991; Y[nA]=0.43+15.36x[lactate, mM]) and 0.25 mM for glutamate (R=0.999; Y[nA]=0.02+29.14x[glutamate, mM]). The developed microbiosensors exhibited also negligible influences from interfering compounds at their physiological concentrations. Microbiosensors remained stable during 10h in a flow injection system at 36 degrees C and pH 7.4. The microbiosensors developed are now used in vivo and, as an example, we report here the data obtained with the glucose biosensor.
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PMID:Highly selective microbiosensors for in vivo measurement of glucose, lactate and glutamate. 1772 13

Analysis of phloem exudates from the fruit of Cucurbitaceae revealed the presence of several compounds with UV-visible absorption spectra identical to that of l-ascorbic acid. In Cucurbita pepo L. (zucchini), the compounds could be isolated from phloem exudates collected from aerial parts of the plant but were not detected in whole tissue homogenates. The compounds isolated from the phloem exudates of C. pepo fruit were eluted from strong anion exchange resin in the same fraction as l-ascorbic acid and were oxidised by ascorbate oxidase (E.C. 1.10.3.3). The major compound purified from C. pepo fruit exudates demonstrated similar redox properties to l-ascorbic acid and synthetic 6-O-glucosyl-l-ascorbic acid (6-GlcAsA) but differed from those of 2-O-glucosyl-l-ascorbic acid (2-GlcAsA) isolated from the fruit of Lycium barbarum L. Parent and fragment ion masses of the compound were consistent with hexosyl-ascorbate in which the hexose moiety was attached to C5 or C6 of AsA. Acid hydrolysis of the major C. pepo compound resulted in the formation of l-ascorbic acid and glucose. The purified compound yielded a proton NMR spectrum that was almost identical to that of synthetic 6-GlcAsA. A series of l-ascorbic acid conjugates have, therefore, been identified in the phloem of Cucurbitaceae and the most abundant conjugate has been identified as 6-GlcAsA. The potential role of such conjugates in the long-distance transport of l-ascorbic acid is discussed.
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PMID:Ascorbic acid conjugates isolated from the phloem of Cucurbitaceae. 1847 16

An amperometric glucose ring-disk biosensor based on a ruthenium complex mediator of low redox potential was fabricated and evaluated. This thin-layer radial flow microsensor (10mul) with ring-disk working electrode displayed remarkable amperometric sensitivity. For Ru(3)(mu(3)-O)(AcO)(6)(Py)(3)(ClO(4)) (Ru-Py), a trinuclear oxo-acetate bridged cluster, a reversible redox curve of low redox potential and narrow potential window (redox potentials were -0.190 and -0.106V versus Ag/AgCl wire, respectively) was observed, which is comparable to many reported mediators such as ferrocene derivatives and other ruthenium complexes. The glucose and hydrogen peroxide assays were carried out with this complex-modified electrode Ru-Py-HRP-GOx/Nafion. The sensitivity was obtained 24nA (15.4mAM(-1)cm(-2)) for 10muM glucose and 126 nA (160mAM(-1)cm(-2)) for 5muM H(2)O(2), respectively with a working potential at 0V versus Ag/AgCl. Ascorbic acid was studied as interference to the glucose assay. The application of 0V potential versus Ag/AgCl did not avoid the occurrence of the oxidation of ascorbic acid, however, the pre-coating of ascorbate oxidase on the disk part of the ring-disk working electrode efficiently pre-oxidized the ascorbic acid and hence eliminated its interference on the glucose response. The practical reliability was also evaluated by assaying the dialysate from the prefrontal cortex of Wistar rats.
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PMID:Evaluation of an amperometric glucose biosensor based on a ruthenium complex mediator of low redox potential. 1897 Jan 6

This study demonstrates a new electroanalytical method with a high physiological relevance for simultaneous online monitoring of glucose and lactate in the striatum of the rat brain following global cerebral ischemia/reperfusion. The online analytical method is based on the efficient integration of in vivo microdialysis sampling with an online selective electrochemical detection with the electrochemical biosensors with dehydrogenases, i.e., glucose and lactate dehydrogenases, as recognition elements. The dehydrogenase-based electrochemical biosensors are developed onto the dual split-disk plastic carbon film (SPCF) electrodes with methylene green (MG) adsorbed onto single-walled carbon nanotubes (SWNTs) as the electrocatalyst for the oxidation of dihydronicotiamide adenine dinucleotide (NADH) at a low potential of 0.0 V (vs Ag/AgCl). Artificial cerebrospinal fluid (aCSF) containing NAD(+) is externally perfused from a second pump and online mixed with the brain microdialysates to minimize the variation of pH that occurred following the cerebral ischemia/reperfusion and to supply NAD(+) cofactor and O(2) for the enzymatic reactions of dehydrogenases and ascorbate oxidase, respectively. As a result, the developed online electroanalytical method exhibits a high selectivity against the electrochemically active species endogenously existing in the cerebral systems and a high tolerance against the variation of pH and O(2) following cerebral ischemia/reperfusion. This property, along with the good linearity and a high stability toward glucose and lactate as well as little cross-talk between two biosensors, substantially makes this method possible for the continuous, simultaneous, and online monitoring of glucose and lactate in the rat brain following global cerebral ischemia/reperfusion. This study establishes a new and effective platform for the investigation of the energy metabolism in physiological and pathological processes.
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PMID:Physiologically relevant online electrochemical method for continuous and simultaneous monitoring of striatum glucose and lactate following global cerebral ischemia/reperfusion. 1928 Dec 58

In order to characterize the functions of the sweetpotato SRF1 gene, which encodes a Dof zinc finger transcriptional factor preferentially expressed in the storage roots, we isolated its full length cDNA and produced transgenic sweetpotato plants with altered SRF1 expression levels. The isolated cDNA of SRF1 encoded a polypeptide of 497 amino acids and was closely related to the cyclic Dof factors of Arabidopsis and the ascorbate oxidase binding protein of pumpkin. SRF1 was most highly expressed in storage roots, although some expression was also observed in other vegetative tissue. Transgenic plants overexpressing SRF1 showed significantly higher storage root dry matter content compared to the original cultivar Kokei No. 14 or control transgenic plants. In these plants, the starch content per fresh weight of the storage roots was also higher than that of the wild-type plants, while the glucose and fructose content drastically decreased. Among the enzymes involved in the sugar metabolism, soluble acid invertase showed a decreased activity in the transgenic plants. Gene expression analysis showed that the expression of Ibbetafruct2, which encodes an isoform of vacuolar invertase, was suppressed in the transgenic plants overexpressing the SRF1 gene. These data suggest that SRF1 modulates the carbohydrate metabolism in the storage roots through negative regulation of a vacuolar invertase gene.
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PMID:Altered carbohydrate metabolism in the storage roots of sweet potato plants overexpressing the SRF1 gene, which encodes a Dof zinc finger transcription factor. 1961 8

The regulation of carbon allocation between photosynthetic source leaves and sink tissues in response to stress is an important factor controlling plant yield. Ascorbate oxidase is an apoplastic enzyme, which controls the redox state of the apoplastic ascorbate pool. RNA interference was used to decrease ascorbate oxidase activity in tomato (Solanum lycopersicum L.). Fruit yield was increased in these lines under three conditions where assimilate became limiting for wild-type plants: when fruit trusses were left unpruned, when leaves were removed or when water supply was limited. Several alterations in the transgenic lines could contribute to the improved yield and favour transport of assimilate from leaves to fruits in the ascorbate oxidase lines. Ascorbate oxidase plants showed increases in stomatal conductance and leaf and fruit sugar content, as well as an altered apoplastic hexose:sucrose ratio. Modifications in gene expression, enzyme activity and the fruit metabolome were coherent with the notion of the ascorbate oxidase RNAi lines showing altered sink strength. Ascorbate oxidase may therefore be a target for strategies aimed at improving water productivity in crop species.
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PMID:A diminution in ascorbate oxidase activity affects carbon allocation and improves yield in tomato under water deficit. 2272 3

The catalysis of ascorbic acid (AsA) oxidation by anion-exchangers modified with metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4]A-500, Me=Mn(3+), Fe(3+), Co(3+), Ce(4+), Cu(2+), Zn(2+), Ni(2+), and H2) were investigated. Me-TCAS[4]A-500 (Me=Mn(3+), Fe(3+), Ce(4+), and Cu(2+)) all exhibited the ability to catalyze the oxidative reaction of AsA to dehydroascorbic acid. However, in the presence of high concentrations of AsA, only Cu(2+)-TCAS[4]A-500 was capable of complete oxidation of the acid. Moreover, after six repeat uses, Cu(2+)-TCAS[4]A-500 maintained high and relatively constant catalytic activity. Prior treatment of glucose solutions with Cu(2+)-TCAS[4]A-500, even in the presence of high AsA concentrations, enabled the satisfactory determination of glucose without interference by AsA. Cu(2+)-TCAS[4]A-500 will therefore be applicable as an artificial substitute for ascorbate oxidase, and may be useful as a means to eliminate AsA interference during the analysis of vital compounds such as glucose and uric acid.
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PMID:Catalytic activity of thiacalix[4]arenetetrasulfonate metal complexes on modified anion-exchangers for ascorbic acid oxidation. 2399 57

Washing processes, essential in most heterogeneous labeled assays, have been a big hurdle in simplifying the detection procedure and reducing assay time. Nevertheless, less attention has been paid to washing-free heterogeneous labeled assays. We report a purely washing-free immunosensor that allows fast, sensitive, and single-step detection of prostate-specific antigen in serum with low interference. Proximity-dependent electron mediation of ferrocenemethanol (Fc) between an indium-tin oxide (ITO) electrode and a glucose-oxidase (GOx) label allows us to discriminate between a bound and an unbound label: a bound label offers faster electron mediation than an unbound one. The electrooxidation of Fc at a low applied potential (0.13 V vs Ag/AgCl) and a low electrocatalytic ITO electrode and the oxidation of l-ascorbic acid by l-ascorbate oxidase minimize the effect of the interfering species. With a high concentration of glucose (200 mM), the signal and background levels are hardly dependent on the glucose-concentration variation in the sample. The washing-free immunosensor can detect a concentration of ca. 1 pg/mL for mouse IgG in phosphate-buffered saline and a concentration of ca. 10 pg/mL for prostate-specific antigen spiked in female serum after an incubation period of 10 min. The concentrations measured with actual clinical serum samples are in good agreement with the concentrations measured with a commercial instrument, which renders the washing-free heterogeneous immunosensor appealing for practical use.
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PMID:Washing-free heterogeneous immunosensor using proximity-dependent electron mediation between an enzyme label and an electrode. 2475 36


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