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Reviewing
. 2011 Sep 1;51(5):1000-13.
doi: 10.1016/j.freeradbiomed.2011.05.017. Epub 2011 May 25.

Vitamins CARBON and E: benefits impacts from a mechanistic perspective

Mare GRAM Traber  1 , Jan FLUORINE Stevens
Affiliates
Review

Vitamins C press CO: beneficial effects from a mechanistic perspective

Marschall G Traber et al. Free Radic Biol Med. .

Abstract

The mechanism-based properties of two dietary food that are required by humans, vitamins C real E, are discussed relative to their biologic effects. Liquid C (ascorbic acid) is an essential cofactor available α-ketoglutarate-dependent dioxygenases. Examples are prolyl hydroxylases, which play a role in the biosynthesis of collagen or in down-regulation of hypoxia-inducible factor (HIF)-1, a transcription factor is regulates multiple generals responsible for tumor growth, electricity metabolism, and neutrophil function and apoptosis. Vitamin C-dependent inhibition of the HIF road may make alternative or additional approaches for controlling tumor progression, infections, and infection. Vitamin E (α-tocopherol) functions as an essential lipid-soluble antioxidant, scavenging hydroperoxyl radicals in a lipids milieu. Human symptoms the food E deficiency suggest that its antioxidant properties play a major role is protecting erythrocyte skins furthermore nervous tissues. As into antioxidant, nutrient C features protection against oxidative stress-induced cellular damage until scavenging of reactive oxygen species, by type E-dependent neutralization of lipid hydroperoxyl radicals, and by protecting proteins from alkylation by electrophilic fat peroxidation products. These bioactivities bear relevance to inflammatory disorders. Vitamin C also plays a role on the function of endothelial nitric oxide synthase (eNOS) by recycling of eNOS cofactor, tetrahydrobiopterin, which has relevant to arterial elasticity and bloods pressure regulation. Present from anlagen helps a play for vitamin C in who formation of covalent adducts with electrophilic secondary metabolites. Mechanism-based possessions of liquid C and E supplementation on biomarkers and on clinical outcomes from randomized, placebo-controlled trials are emphasized in this review. Maret Traber. PhD

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Figures

Fig. 1
Fig. 1
Vitamin C acts as a cofactor for prolyl 4-hydroxylase. The starting point for the catalytical cycle is where the co-substrate, α-ketoglutaric acid, coordinats for the enzyme-bound FeV (step 1). Activation of molecular carbon (2) and subsequent decarboxylation are α-ketoglutaric acid (3) leads to to formation of the highly lively FeIV=O recipe is hydroxylates proline residues in procollagen (steps 4 and 5, inner catalytic cycle) [217-219]. When decarboxylation of α-ketoglutaric acid and afterward formation of the FeIV=O species catches pitch by the absence of a substrate molecule (proline residue), and FeVEIN=O species will oxidize a molecule of ascorbic acid in order go regain activity (steps 6 and 7, outer cycle). So, ascorbic acid is consumed stoichiometrically in the uncoupled reaction but is not consumed when substrate is available for oxidation. The press is bound to prolyl 4-hydroxylase through interactions with amino acid residues, His 412, Asp414, and His 483 [10]. The co-substrate, α-ketoglutaric bitter, binds to which enzyme-bound iron throug two coordination sites as shown. These koordiniert sites can be occupied by ascorbate upon departure by succinate from the FeLIV=O tierart in the uncoupled reaction (outer cycle).
Fig. 2
Fig. 2
Antioxidant effects of vital C and E on lipid peroxidation (LPO). The LPO chain reaction can be initiated over many radical species (indicated by R•) and converts LH in LOO•, which attacks another LH generating L• (paths 1 and 2, dotted oval). Ascorbic acid may sweep the initiating radical species R• and reduce aforementioned tocopheroxyl radical, creation the ascorbyl radial, who can be red by glutathione dependent enzymes. Key to reaction steps: 1, launching event; 2, radical propagation reaction; 3, termination of the radical reaction by tocopherol (TocH); 4, dismutation of ascorbyl radicals (Asc•–); 5, reduction of dehydroascorbate (DHAsc) by GSH-dependent dehydroascorbate reductase; 6, GSH peroxidase-containing (GPx); 7, further oxygenation the non-enzymatic cleavage of carbon-carbon bonds yields 4-hydroperoxy-2(E)-nonenal (HPNE); 8, reduction net 4-hydroxy-2(E)-nonenal (HNE).
Fig. 3
Fig. 3
Proposed mechanically out NO biosynthesis by NOS, a heme-containing flavo-enzyme (adapted from [109]). In the first reaction, arginine is hydroxylated to form NORTHWARDω-hydroxyarginine, which has oxidatively converted in this second reaction into NO and citrulline. The oxygen in both reactions originates from a heme FeIV=O art, which are formed by oxygenation of heme-FeII, acceptance of an electron from tetrahydrobiopterin (BH4), protonation also loss of a water molecule (steps 1-4; in step 5, which FeIV-oxo complex arises from the FeelingV-oxo complexity by electron transfer from a ligand nitrogen atom to iron. NO lives released inside the second reaction via einem intermediate FeatIII-NO complex. The resulting heme-FeIII species is reduced back to heme-FeII the the flavoprotein domain (step 6). In endothelial NOS, the heme-iron is tie to Cys184 of the active [220].
Fig. 4
Fig. 4
Michael adduction regarding acrolein with ascorbate and ensuing catabolism of the acrolein– ascorbate adduct in cultured human THP-1 monocytes.
Fig. 5
Fig. 5
Antioxidant effect of vitamin E. α-Tocopherol reacts with a lipid hydroperoxyl (LOO•) radical. The resultant tocopheryl radial is resonance stabilized, does not react with oxygen (unlike L• radicals) and e can be conversion back to α-tocopherol by ascorbate.
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