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2 edition of metabolic consequences of ascorbate biosynthesis in the rat. found in the catalog.

metabolic consequences of ascorbate biosynthesis in the rat.

Tom Sze-Yin Chan

metabolic consequences of ascorbate biosynthesis in the rat.

by Tom Sze-Yin Chan

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Published .
Written in English


About the Edition

This thesis explores the antioxidant and metabolic consequences of ascorbate biosynthesis in rat hepatocytes. Following chapter 1 (the introduction), chapter 2 explores glutathione (GSH) conjugation and oxidation-induced ascorbate synthesis by identifying 2 GSH-transferase substrates that rapidly deplete GSH and stimulate ascorbate synthesis. In addition, some novel biochemical observations were noted. Ascorbate synthesis was accompanied by rapid glycogenolysis without glucose synthesis and could not be stimulated by the GSH oxidant, diamide. This was contradictory to a past hypothesis that cellular oxidized GSH increased glycogenolysis and thus ascorbate synthesis. Chapter 3 illustrates for the first time that endogenously produced ascorbate can protect against oxidative stress triggered by the organoperoxide, cumene hydroperoxide (CHP). This chapter describes the beneficial, antioxidant activity of endogenous ascorbate synthesis which could supplant the antioxidant role of GSH under oxidative stress conditions. Induction of cellular susceptibility to low concentrations of CHIP was accomplished by depleting GSH. However, the depletion of GSH was also associated with ascorbate synthesis and the synthesised ascorbate was found to significantly protect cells against CHP-mediated reactive oxygen species production, cell death and lipid peroxidation. This ascorbate protective effect was successfully abolished by an inhibitor of ascorbate biosynthesis and did not occur with guinea pig hepatocytes which were unable to carry out ascorbate synthesis. Chapter 4 explores the biochemical changes associated with xenobiotic-induced ascorbate synthesis. This chapter follows from chapter 1 by delineating the potential bioenergetic cost of ascorbate synthesis. High resolution NMR spectroscopy with 13C-labeled glucose was used to identify metabolic fluxes of carbohydrates through glycogenolysis, glycogen synthesis, gluconeogenesis, and glycolysis in the presence of chloretone, a known inducer of ascorbate synthesis. Surprisingly, chloretone caused dramatic decreases in both glycolysis and gluconeogenesis and glycogen synthesis. This was accompanied by a significant increase in 13C labeled ascorbate in the cell and a lowered ability to glucuronidate acetaminophen. These results suggest that the xenobiotic-mediated increase in ascorbate synthesis involves a dramatic redirection of glucose units into the D-glucuronic acid pathway. Since the metabolic regulatory mechanism involves all major pathways of glucose metabolism, the work described in this thesis is also important for non-ascorbate synthesing organisms.

The Physical Object
Pagination147 leaves.
Number of Pages147
ID Numbers
Open LibraryOL19475703M
ISBN 100494028777

  Ascorbate (vitamin C) can reach very high concentrations in chloroplasts (20– mM).The pool size in leaves and chloroplasts increases during acclimation to high light intensity and the highest concentrations recorded are in high alpine by: L-ascorbate is the L-enantiomer of ascorbate and conjugate base of L-ascorbic acid, arising from selective deprotonation of the 3-hydroxy ed for a range of essential metabolic reactions in all animals and plants. It has a role as a human metabolite, a Daphnia magna metabolite, a cofactor and a water-soluble is a conjugate base of a L-ascorbic acid.

  Cysts of the brine shrimp (Artemia salina) during various hydration states were analyzed for ascorbate concentration. At a state of cellular dehydration and metabolic arrest, ascorbate is stored in the form of stable ascorbic by: Summary: General Background. L-ascorbate, also known as vitamin C, fulfils multiple essential roles in both plants and a strong reducing agent, it functions as an antioxidant and a redox buffer. It is also a cofactor for several enzymes, which are involved in many important pathways, including collagen hydroxylation, carnitine biosynthesis, norepinephrine biosynthesis, and.

  Ascorbate (AsA), the most abundant water-soluble redox compound in plants and eukaryotic algae, has multiple functions. There is compelling genetic evidence that the biosynthesis of AsA proceeds via a D-mannose/ L-galactose pathway and is the most significant source of AsA in plays important roles in antioxidative defense, particularly via the AsA/glutathione by:   An attempt was made to unravel further the mechanism by which high dietary concentrations of ascorbic acid influence copper metabolism. The addition of ascorbic acid to the diet of rats caused about a twofold increase in plasma ascorbate concentrations and reduced group mean plasma and tissue concentrations of by:


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Metabolic consequences of ascorbate biosynthesis in the rat by Tom Sze-Yin Chan Download PDF EPUB FB2

One pathway of ascorbate biosynthesis starting from glucose has been fully documented in higher plants, named the l-galactose pathway [10, 11••, 12], and all the genes in the biosynthetic pathway have been identified ().All identified regulatory genes reviewed here relate to this l-galactose least in Arabidopsis the route through l-galactose appears to be the by far the dominant Cited by:   Abstract.

Ascorbate is the most abundant water-soluble redox compound in plants and has multiple functions as a redox buffer. There is compelling genetic evidence that the biosynthesis of ascorbate proceeds via the d-mannose/ l-galactose pathway and is the most significant source of ascorbate in ative pathways, including those via d-galacturonate and d-glucuronate, have Cited by: 3.

Pathways to L-ascorbate in plants. L-Ascorbate (or vitamin C) is an essential enzyme cofactor in hydroxylation and other reactions as well as a primary antioxidant in both plants and animals [].Since a few animal species (including primates) have lost the capacity for L-ascorbate synthesis [], they are dependent upon diet to ensure adequate levels for metabolism and oxidative by:   Bartoli CG, Pastori GM, Foyer CH.

Ascorbate biosynthesis in mitochondria is linked to the electron transport chain between complexes III and IV. Plant Physiol. May; (1)– [PMC free article] Beck E, Burkert A, Hofmann M. Uptake of l-Ascorbate by Intact Spinach Chloroplasts.

Plant Physiol. Sep; 73 (1)–Cited by: In contrast to its relatively fast reaction with superoxide and other radicals, ascorbate reacts slowly with H 2 O 2 (rate constant 2 M-1 s-1 at pH 7).In green plants and a number of other photosynthetic protists, H 2 O 2 removal is catalysed by a specialised family of haem containing ascorbate peroxidases (APXs).

Although APX activity has been reported in a number of non-plants, it appears Cited by: Vitamin C, also known as ascorbic acid and ascorbate, is a vitamin found in various foods and sold as a dietary supplement. It is used to prevent and treat scurvy. Vitamin C is an essential nutrient involved in the repair of tissue and the enzymatic production of certain neurotransmitters.

It is required for the functioning of several enzymes and is important for immune system ncy category: A (to RDA), C (above RDA). Ascorbic acid is also frequently reported to affect plant growth and development e.g. flowering time and fruit ripening.

The scope of the book is to cover the biological role, biosynthesis and metabolism, regulation, and metabolic modification of ascorbate in : Springer-Verlag New York. Ascorbate is the most abundant water-soluble redox compound in plants and has multiple functions as a redox buffer.

There is compelling genetic evidence that the biosynthesis of ascorbate proceeds. l-Galactono-1,4-lactone dehydrogenase (EC [][1]) catalyzes the last step in the main pathway of vitamin C (l-ascorbic acid) biosynthesis in higher plants. In this study, we first characterized the spatial and temporal expression of SlGalLDH in several organs of tomato (Solanum lycopersicum) plants in parallel with the ascorbate content.

Introduction. Ascorbate (Asc, also called vitamin C) is of vital importance to the cellular functions of both animals and plants. It is an essential scavenger of reactive oxygen species (ROS), such as singlet oxygen (1 O 2) and superoxide anions, and it is also a cofactor of several 2‐oxoacid‐dependent dioxygenase enzymes, which catalyze a large number of enzymatic reactions in the by: ascorbate and aldarate metabolic pathway - Ontology Report - Rat Genome Database ascorbate and aldarate metabolic pathway: go back to main search page.

Accession: PW browse the term: Definition: Those metabolic reactions involved in the synthesis, utilization and/or degradation of ascorbate and aldarate, as depicted in the KEGG. Biosynthesis of L-ascorbate (vitamin C) occurs by different pathways in plants and mammals.

Yeast contain D-erythroascorbate, a C5 analog of : Nicholas Smirnoff. Myoinositol synthesis and catabolism are crucial in many multiceullar eukaryotes for the production of phosphatidylinositol signaling molecules, glycerophosphoinositide membrane anchors, cell wall pectic noncellulosic polysaccharides, and several other molecules including ascorbate.

Myoinositol monophosphatase (IMP) is a major enzyme required for the synthesis of myoinositol and the. Abstract. Ascorbate is the major soluble antioxidant found in plants and is also an essential component of human nutrition.

Evidence suggests that the plasma levels of ascorbate in large sections of the population are sub-optimal for the health protective effects of this : Yuyang Zhang. Abstract.

Using mouse gene knock-out models, we identify aldehyde reductase (ECAkr1a4 (GR)) and aldose reductase (ECAkr1b3 (AR)) as the enzymes responsible for conversion of d-glucuronate to l-gulonate, a key step in the ascorbate (ASC) synthesis pathway in gene knock-out (KO) mice show that the two enzymes, GR and AR, provide ∼85 and ∼15% Cited by: Recent Advances in Ascorbate Biosynthesis and the Physiological Significance of Ascorbate Peroxidase in Photosynthesizing OrganismsThis review was written in response to the receipt of The Japan Bioscience, Biotechnology, and Agrochemistry Society Award.

L-Ascorbate biosynthesis in higher plants: the role of VTC2 Carole L. Linster and Steven G. Clarke Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Charles E.

Young Drive East, Los Angeles, CAUSA Inthepastyear,thelastmissingenzymeoftheL-galactose. ascorbate, ascorbate plus radiation, and H2O2 treatments induced both genotoxic and metabolic stress.

Exposure to high dose ascorbate blocked DNA synthesis in both DNA damaged and undamaged cell of ascorbate sensitive GBM cell lines.

H2O2 treatment blocked DNA synthesis in all cell lines with and without DNA by: 8. Ascorbate doses that maximally stimulated collagen production ( μ M) antagonized elastin biosynthesis in vascular smooth muscle cells and skin fibroblasts, depending on a combination of dose and exposure time.

Diminished elastin production paralleled reduced elastin mRNA levels, while collagen I and III mRNAs levels by: essential for ascorbate synthesis, in the brain of the African lungfish, Protopterus annectens. This report provides an up-to-date review on ascorbate synthesis in fishes and the possible future directions of study in view of the discovery of the unusual site of ascorbate biosynthesis.

VC IUBMB Life, 67(2)–76, Cited by: 3. Ascorbate (AsA), the most abundant water-soluble redox compound in plants and eukaryotic algae, has multiple functions. There is compelling genetic evidence that the biosynthesis of AsA proceeds via a D-mannose/L-galactose pathway and is the most significant source of AsA in plays important roles in antioxidative defense, particularly via the AsA/glutathione by: ; Native ascorbate oxidase from Cucurbita species.

Catalyzes the oxidation of ascorbioxidation of ascorbic acid to dehydroascorbic acid. Suitable for eliminating interference of ascorbic acid in clinical assays and for determination of ascorbic acid.Ascorbate, or vitamin C, is obtained by humans mostly from plant sources.

Various approaches have been made to increase ascorbate in plants by transgenic means. Most of these attempts have involved leaf material from model plants, with little success reported using genes from the generally accepted l ‐galactose pathway of ascorbate by: