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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Y79 human retinoblastoma cells have a high capacity to reduce ascorbate autooxidation rates through the reduction of the ascorbate free radicals generated in the oxidation process. Responsible of this capacity is a plasma membrane redox system, which might be functionally related to the Na+/H+ antiporter. Ascorbate has cytotoxic effect on Y79 cells in long-term incubations in the presence of limited amounts of serum in the medium.
Biochem Mol Biol Int 1993 Apr
PMID:A plasma membrane redox system in human retinoblastoma cells. 838 32

To determine the regulatory role of prolyl hydroxylation in intracellular cardiac procollagen turnover, we examined the effects of prolyl 4-hydroxylase inhibitors (alpha, alpha-dipyridil, 3,4-dihydroxybenzoic acid ethyl ester, pyridine 2,4-dicarboxylic acid ethyl ester) and ascorbic acid on procollagen metabolism by cultured, neonatal rat cardiac fibroblasts. Ascorbate-deficient fibroblasts showed decreased rates of prolyl hydroxylation and total collagen accumulation without a significant reduction in alpha 1(I) and alpha 1(III) mRNA levels. The fraction of newly synthesized procollagens degraded intracellularly was also substantially increased in ascorbate-deficient cells (50 +/- 7 v 30 +/- 3% in ascorbate-deficient v control fibroblasts; P < 0.05). These findings were associated with increased intracellular accumulation of Type I procollagen, enhanced secretion of "underhydroxylated" pro alpha 1 (I) polypeptide into the cell culture medium, and decreased extracellular Type I collagen deposition. Similar results were obtained by treating cells with alpha, alpha-dipyridil (300 microns), and 3,4-dihydroxybenzoic acid ethyl ester (400 microM) in the presence of ascorbate. A major portion of the enhanced degradation of newly synthesized procollagens occurred within acidic intracellular compartments as indicated by the inhibition of procollagen degradation by chloroquine (25 microM). Inhibition of procollagen secretion by colchicine (0.5 micrograms/ml) enhanced the diversion to, and subsequent intracellular degradation of underhydroxylated procollagens in cardiac fibroblast lysosomes. We conclude that inactivation of prolyl 4-hydroxylase increases intracellular accumulation and intralysosomal degradation of newly synthesized cardiac procollagen polypeptides. These observations suggest that procollagen prolyl hydroxylation may be important in the regulation of collagen accumulation by cardiac interstitial cells during fibrotic processes in vivo
J Mol Cell Cardiol 1995 Aug
PMID:Prolyl hydroxylation regulates intracellular procollagen degradation in cultured rat cardiac fibroblasts. 852 10

The effects of ozone or sulfur dioxide on antioxidant enzymes were investigated in Arabidopsis thaliana. Plants were fumigated with 0.1-0.15 ppm ozone or sulfur dioxide up to about 1 week in an environment-controlled chamber. Both pollutants increased the activities of ascorbate peroxidase and guaiacol peroxidase in leaves, but had little effect on the activities of superoxide dismutase, catalase, monodehydroascorbate reductase, dehydroascorbate reductase or glutathione reductase. Ozone was more effective than sulfur dioxide in increasing the activities of the peroxidases. Ascorbate peroxidase activity increased 1.8-fold without a lag period during fumigation with 0.1 ppm ozone, while guaiacol peroxidase activity increased 4.4-fold with a 1-day lag. Expression of the APX1 gene encoding cytosolic ascorbate peroxidase was further investigated. Its protein levels in leaves exposed to 0.1 ppm ozone for 4 or 8 days were 1.5-fold higher than in controls. Both ozone and sulfur dioxide elevated APX1 mRNA levels in leaves at 4 and 7 days, whereas at 1 day only ozone was effective. The induction of APX1 mRNA levels by ozone (3.4- to 4.1-fold) was more prominent than that by sulfur dioxide (1.6- to 2.6-fold). The APX1 mRNA level increased by day and decreased by night. Exposure of plants to 0.1 ppm ozone enhanced the APX1 mRNA level within 3 h, which showed a diurnal rhythm similar to that of the control. These results demonstrate that near-ambient concentrations of ozone as well as similar concentrations of sulfur dioxide can induce APX1 gene expression in A. thaliana.
Plant Mol Biol 1995 Nov
PMID:Expression of Arabidopsis cytosolic ascorbate peroxidase gene in response to ozone or sulfur dioxide. 853 47

The effect of baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one), a flavonoid isolated from Scutellaria baicalensis Georgi, on lipid peroxidation in rat liver microsomes was studied. Ascorbic acid-induced lipid peroxidation in microsomes obtained from baicalein-treated rats was inhibited by treatment on different days and at different doses. Iron release induced by ascorbic acid from microsomes of baicalein-treated rats was markedly lower than from microsomes of control rats. However, no statistical differences in total, nonheme and nonprotein-bound (free iron) iron contents could be detected in the two microsomes. The degradation of calf thymus DNA, an indicator of free iron existence, was observed in the reactions of microsomes obtained from control and baicalein-treated rats with ascorbic acid in the presence of bleomycin. These results suggest that baicalein can inhibit lipid peroxidation in microsomes induced by ascorbic acid by forming an inert complex of iron.
Res Commun Mol Pathol Pharmacol 1995 Oct
PMID:Protection by baicalein against ascorbic acid-induced lipid peroxidation of rat liver microsomes. 858 35

A modified version of a previously published extraction technique using acetone as the extracting medium and separation on an HPLC equipped with a Spherisorb C18 ODS2 column packed with 3 micron particles along with a suitable flow rate and mobile phase significantly improves the resolution of the chromatographic output (fluorescence detector), allowing for accurate measurement of alpha-, delta- and gamma(+ beta)-tocopherols. It was found that two extractions of the same sample yielded approximately 97% of the total extractable alpha-tocopherol. Vitamin C was not needed as an anti-oxidant to protect alpha-tocopherol during extraction from chicken liver but was needed when using fish liver. alpha-tocopherol was found not to be evenly distributed in beef, chicken or fish liver.
Comp Biochem Physiol B Biochem Mol Biol 1996 Jan
PMID:Determination of alpha-, gamma(+ beta)-, and delta-tocopherols in a variety of liver tissues by reverse-phase high pressure liquid chromatography. 893 47

Of TGF-beta superfamily proteins, BMP-2 enhanced alkaline phosphatase (ALP) activity in cultured osteoblastic cells, MC3T3-E1, to the same level promoted by ascorbate, whereas TGF-beta s (beta 1, beta 2, beta 3) reduced ALP activity and altered cell morphology under the same conditions. Activin appeared to have no distinct effect on ALP synthesis. Ascorbate dependent increase in ALP synthesis was markedly stimulated in the presence of BMP-2. The synergistic effect of ascorbate on ALP synthesis was replaced by type I collagen coated on the culture dish. However, BMP-2 appeared not to bind to type I collagen. These findings indicate that BMP-2 acts directly on osteoblastic cells through its receptors and collagenous matrix can neither recruit BMP-2 nor modulate directly the action of BMP-2 in the pericellular area. Treatment of cells grown in ascorbate media with TGF-beta s decreased rapidly the cellular ALP activity indicating that TGF-beta s direct cells to the dedifferentiated stage.
Mol Cell Biochem 1996 Dec 06
PMID:Synergistic effect of BMP-2 and ascorbate on the phenotypic expression of osteoblastic MC3T3-E1 cells. 897 78

Oxidative damage (lipid peroxidation, LPO) induced in a completely defined system containing glutathione (GSH), purified gamma-glutamyl transpeptidase (GGT), and EDTA- and ADP-chelated ferric iron was enhanced by catalytic amounts of cupric ions and by ceruloplasmin (CP). The enhancement depended on GSH concentration, GGT activity, the presence of iron, and the chelation of copper by o-phenanthroline. High concentrations of CP inhibited LPO. Cu- and CP-enhanced, GSH-GGT-driven LPO was inhibited by the chain-breaking radical scavengers butylated hydroxyanisol, alpha-tocopherol, and Trolox C (a synthetic analog of alpha-tocopherol) but not by the hydroxyl scavenger mannitol. Ascorbic acid increased LPO in the presence of Cu or CP. Cu-enhanced LPO was partially sensitive to superoxide dismutase but not to catalase or horseradish peroxidase. The results indicate that Cu and CP enhance thiol-driven LPO and promote thiol-dependent mutagenesis by a very similar, if not the same, mechanism and are in agreement with the idea that this enhancement is due to redox reactions of chelated Cu and Fe, rather than to the reactivity of Cu in the Fenton reaction.
Environ Mol Mutagen 1997
PMID:Promotion of glutathione-gamma-glutamyl transpeptidase-dependent lipid peroxidation by copper and ceruloplasmin: the requirement for iron and the effects of antioxidants and antioxidant enzymes. 902 Mar 10

The cytochrome P-450 monooxygenase system plays a central role in the oxidation of a wide variety of structurally unrelated compounds. Its contribution is affected by nutritional and several other factors. Ascorbic acid (AA) deficiency decreases the content of cytochrome P-450 in liver microsomes of guinea pigs (GPs). Included in the group of cytochromes P-450 are the phenobarbital and 3-methylcholanthrene inducible moieties. In the present study the effect of AA status on another specific cytochrome P-450, CYP4A1, laurate omega-hydroxylase was investigated. Ascorbic acid may selectively increase or decrease certain forms of cytochromes. For four weeks adult male Hartley GPs were fed a diet containing 2.5 (Group I), 0.1 (Group II) and 0% (Group III) AA. The liver microsomes were isolated at this stage and cytochrome P-450 content was determined. Group III showed a significant decrease in cytochrome P-450 compared to groups I and II. They also showed a marked decrease in aminopyrine N-demethylase activity. The expression of CYP4A1 was evaluated using Western blot and anti-CYP4A1 antibody. Group III GPs showed a marked decrease in CYP4A1 expression. Groups I and II showed similar expression. This study demonstrates that CYP4A1, a specific cytochrome induced by hypolipidemic agents, is decreased by AA deficiency.
Res Commun Mol Pathol Pharmacol 1997 Jan
PMID:Ascorbic acid deficiency decreases the expression of CYP4A1 in liver microsomes of guinea pigs. 905 44

Ascorbic acid displays the characteristics of an ideal inducer of tissue-specific function in primary avian tendon cells in culture. It is a highly specific, potent stimulator of collagen synthesis, it demonstrates slow reversible kinetics, and it has no effect on growth rate of the cultured cells. Kinetic analysis of ascorbate induction of collagen synthesis was used to determine the critical steps in this complex biosynthetic pathway. Full hydroxylation of the proline residues in collagen, although probably a necessary step for collagen induction, was in itself not sufficient for achieving either increased secretion or increased synthesis. On the other hand, an increase in secretion rate, which required both the presence of ascorbate and a high cell density, did correlate with the later stimulation in procollagen production. The process of procollagen secretion, therefore, meets the minimal requirements for the rate-limiting step. The fact that the cells maintained a large pool of intracellular procollagen despite changes in the rates of translation or secretion led us to postulate a possible feedback between the level of the internal procollagen pool and the rate of procollagen synthesis.
Mol Cell Biol 1981 Sep
PMID:Ascorbate induction of collagen synthesis as a means for elucidating a mechanism of quantitative control of tissue-specific function. 927 97

An Arabidopsis 14-3-3 protein, AFT1, was used as a 'bait' in the two-hybrid system to identify its interacting proteins. One of the candidate proteins, APX3, was identified as a putative peroxisomal membrane-bound ascorbate peroxidase. Ascorbate peroxidases are important defense enzymes that protect plant cells from oxidative stress damage. DNA blot analysis indicates that APX3 is encoded by a single-copy gene in the Arabidopsis genome. RNA blot analyses show that APX3 transcript levels increase slightly in response to cold, UV light, and treatments with hydrogen peroxide and paraquat. The activity of APX3 in Arabidopsis may be controlled in two ways: its enzymatic activity through protein-protein interactions and its transcription by transcriptional or posttranscriptional regulation.
Plant Mol Biol 1997 Aug
PMID:Cloning and expression of an Arabidopsis gene encoding a putative peroxisomal ascorbate peroxidase. 929 Jun 48


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