
Vitamins and Coenzymes
Ascorbic AcidAscorbic acid, Vitamin C, is a simple carbohydrate that is soluble in water, stable in acid, and destroyed in alkali and oxygen. Within the body, ascorbic acid is reversibly oxidized to dehydroascorbic acid, thus forming full biologic activity. Ascorbic acid is a reducing agent involved in numerous oxidation-reduction reactions and transfer of protons. It is essential in the synthesis of collagen, catecholamines, corticosterone, the metabolism of tyrosine, improves nonheme iron absorption, stabilizes cell membranes, helps to maintain the integrity of connective tissue, osteoid tissue of bone, and dentin of teeth. It is an aldose reductase inhibitor, antihistamine effect, delays the insulin response to glucose challenge, exerts vasodilatory, and anti clotting affects by altering the production of prostaglandins. Biotin Biotin is an imidazole derivative consisting of eight isomers. It is a water-soluble B vitamin and can be synthesized by intestinal bacteria and absorbed from the colon. It functions as a CO2 carrier on the surface of ATP enzymes and is a mobile carbozal carrier in the mitochondria as pyruvate, propionyl CoA, 3-methylcrotonyl CoA carboxylases, and acetyl CoA carboylase in the cytosol, which are essential to the metabolism of lipids, CHO, and some amino acids. beta-Carotene Beta-Carotene is an extensive double-bond system capable of stabilizing an odd electron that defines its chemical potential as a free radical scavenger. Beta-Carotene is a precursor to retinol and a carotenoid pigment of pro-Vitamin A plant food products. It has been shown to inhibit peroxidation of linoleic acid by xanthine oxidase, decrease lipid peroxidation, and reduce neutrophil-mediated cell injury as well as the affects of retinoids once it is converted to Vitamin A. Choline Choline is a lipotropic quaternary amine that is water soluble, strongly alkaline, and hygroscopic. It is classified as a "vitamin-like" substance because the body can synthesize it. The endogenous synthesis of choline requires adequate quantities of folic acid, cobalamin, pyridoxine, and the amino acids serine and methionine. Choline is a methyl donor for the synthesis of compounds such as methionine, is an important component of membrane phospholipids, an integral component of normal lung development (as part of surfactant), essential for the synthesis of the neurotransmitter acetylcholine and phosphatidylcholine. Coenzyme Q10 Coenzyme Q contains a quinone ring and a long-chain isoprenoid tail that provides the molecule with its hydrophobic character enabling it to function in lipid environments. Coenzyme Q functions as an electron shuttle as part of the mitochondrial electron transport chain, where it is situated between flavoproteins and cytochromes making it essential to cellular respiration and the production of ATP. It has been shown to be effective in improving cardiac output (as in left ventricular function during myocardial infarction), attenuate the accumulation of lactate through a mechanism hypothesized to promote oxygen utilization under hypoxic conditions, and improve pulmonary function. Folate/Folinic Acid Folate is a water-soluble B vitamin composed of a pteridine ring attached to p-aminobenzoic acid and conjugated to one molecule of glutamic acid. Folate functions as an enzyme co-substrate in many reactions of the metabolism of amino acids and nucleotides. It provides labile methyl groups for methionine synthesis from homocysteine, transports formate for purine synthesis, and formaldehyde for thymidylate synthesis from deoxyuridylate for DNA synthesis. Folic acid is essential for growth and cellular division. It is required for carbon transfer, purine and pyrimidine biosynthesis, amino acid conversions, and maturation of blood cells. Folinic acid may bypass the deconjugation and reduction steps and is converted into 5-methyltetrahydrofolate in enterocytes and absorbed directly. Folinic acid is the most stable of the reduced folates and is more easily transported into the central nervous system than folate. Inositol Inositol, Vitamin B8, is water soluble and is a naturally occurring isomer of glucose that is a key intermediate of the phosphatidyl-inositol cycle, a second messenger system used by several noradrenergic, serotonergic, and cholinergic receptors. In view of the capacity of several tissues to synthesize inositol from D-glucose by the action of inositol-1-phosphatase on inositol-1-phosphate, which is derived from the cyclization of glucose-6-phosphate, no requirement for dietary inositol has been established for humans. Within cells, inositol exists in its free form, as phosphorylated derivatives, and as a constituent of glycosyl-phosphatidyl inositol anchors of membranes proteins as phosphoinositides. Many of its physiologic and biochemical roles have been attributed to the membrane phosphoinositides. The "parent" phospholipid, phosphatidylinositol can modulate the activity of several membrane-bound enzymes, including Na-K adenosine triphosphatase, and medicate transmembrane signaling processes. Phosphatidylinositol signals the release of Ca+2 from organelles as well as entry of Ca+2 into the cells across the cell membrane, involved in the activation of Protein Kinase C, is a component of a novel glycoprotein in the brain that is involved as one of the recognition molecules on neurons that create specific synaptic contacts with appropriate targets during development and is involved in arachadonate metabolism. Nicotinic Acid/Niacin/Niacinamide Nicotinic acid is a monocarboxylic acid derivative of pyridine and niacinamide (Vitamin B3) is the corresponding amine. Both are water-soluble B vitamins. Nicotinic acid functions metabolically as a precursor for the coenzymes NADH and NADPH acting in hydrogen transfers in metabolism with more than 200 reactions in the metabolism of carbohydrates, fatty acids, and amino acids which are essential for a variety of oxidation-reduction reactions. Nicotinic acid serves as a glucose tolerance factor and is used therapeutically to lower serum cholesterol levels. Pantothenic Acid/Pantethine Pantothenic acid is a water-soluble B vitamin that is a dimethyl derivative of butyric acid joined by an essential component of coenzyme A or Pantethine, which participates in enzymatic reactions crucial to the metabolism of fatty acid oxidation, gluconeogenesis, carbohydrates, and the synthesis of sterols, steroid hormones and porphyrins. Pantethine increases fatty acid metabolism in the mitochondria forming high-energy thioester bonds with carboxylic acids. As CoA (and ACP/4'-phosphopentetheine) this coenzyme functions metabolically as a carrier of acyl groups and as Acyl-Carrier Protein (ACP), a component of fatty acid synthase where it functions in transferring covalently bound intermediates between different active sites with successive condensations and reductions. As CoA plays a central role in the modification of cellular proteins with acetyl and fatty acyl groups, modifications that impact the activity, structure and localization of proteins. CoA mediates peptide modification in the attachment of long chain fatty acyl groups to cellular and viral proteins. This modification can impact the protein's ability to participate in the regulatory steps that mediate signal transduction. Pyridoxine/Pyridoxal 5' Phosphate (PLP) Pyridoxine, Vitamin B6, naturally occurs in three closely interrelated compounds: Pyridoxine (alcohol), pyridoxal (aldehyde), and pyridoxamine (amine) and their corresponding phosphates. All forms of pyridoxamine are soluble in water and alcohol. Pyridoxine function involves many complex, multifaceted, interrelated functions that center around amino acid metabolism whereby almost all reactions in amino acid metabolism (via the transaminases) are involved in their biosynthesis as well as their catabolism. Cellular processes involving PLP include immune modulation, fatty acid metabolism, modulation of steroid hormone receptors, biosynthesis of neurotransmitters, gluconeogenesis, and heme synthesis. Quercitin Quercitin is a bioflavinoid that works synergistically with ascorbic acid. It decreases neutrophils lysomal enzyme breakdown by hyaluronidase. Quercitin aids in capillary fragility, inhibits histamine release, and has a membrane stabilizing effect. Riboflavin/Riboflavin 5' Phosphate Riboflavin is a water-soluble vitamin, Vitamin B2 that consists of a heterocyclic isoalloxazine ring attached to a sugar alcohol side chain, ribitol. Riboflavin is phosphorylated into the coenzyme flavin mononucleotide (FMN) and ultimately converted to flavin adenine dinucleotide (FAD). FMN and FAD participate in oxidation-reduction reactions and in energy production via the respiratory chain through electron transfer. Riboflavin is crucial for the metabolism of carbohydrates, amino acids, and lipids. Thiamine Thiamine, Vitamin B1, is a water-soluble vitamin consisting of a pyrimidine ring joined to a sulfur-containing thiazole ring by a methylene bridge. During absorption, thiamine is phosphorylated to the coenzyme thiamine pyrophosphate (TPP) and comprises 80% of the stored vitamin. Thiamine via TPP is an essential cofactor for the cleavage of the C-C bond of alpha-ketoacids (pyruvate) to yield products subsequently transferred to an acceptor. The biological function of thiamine pyrophosphate is the transfer of an acyl carbanion from one compound to another. Each TPP dependent enzyme also requires Mg+2 or another divalent cation for activity. Thiamine (TPP) contributes to nervous system function by catalyzing energy production and biosynthesis of lipids, acetylcholine, and triphosphate; and serves in the maintenance of cardiac, muscular, nervous, and gastrointestinal systems. alpha-Tocopherols alpha-Tocopherol or vitamin E, is an alcohol derived from phytol and trimethyl hydroquinone. Eight tocopherols and tocotrienols with vitamin E activity have been identified, differing from each other in the number and position of methyl groups around the phenol ring of the molecule. Alpha-tocopherol is the most active form of vitamin E which functions as an antioxidant in the body by scavenging free radicals, enhances lymphocyte production, increases nitrogen retention, maintains cellular integrity, and aids in the biosynthesis of heme proteins. Vitamin A Retinoids are isoprenoid compounds found in animal products that serve the visual process here they are involved in the photo sensitive chromophoric group of the visual pigments of rod and cone cells of the retina. Vitamin A, or Retinoid, is fat soluble and its systemic functions include the differentiation and growth of epithelial cells, a role in nuclear receptors for steroid hormones, involvement in glycoprotein synthesis, reproductions, immunocompetence, anti-inflammatory processes, glycocorticoid production, metabolism of bone, and maintenance of mucous membranes, skin, and hair. Vitamin B12 Cobalamin or Vitamin B12 is composed of a central cobalt ion within a porphyrin-like ring (corrin ring), linked to a nucleotide base, ribose, and phosphoric acid. B12 exists in several forms: cyanocobalamin, hydroxycobalamin, methyl cobalamin, and adenosylcobalamin. After ingestion, cobalamin is bound to a protein, intrinsic factor, secreted by gastric parietal cells, where it transits the intestine and attaches to specific receptors in the ileal mucosa. After absorption, cobalamin is bound by transcobalamin II (a plasma protein) for transport to the tissues. Cobalamin is essential for normal hematopoiesis. It is crucial for the maintenance of the integrity of the nervous system (especially myelin formation) and of sulfhydryl groups for many SH-activated enzyme systems, is required for hydrogen transfer, and plays key roles in the metabolism of proprionate, amino acids, and single carbon atoms. Vitamin D Vitamin D3 or cholecalciferol, is the natural form of vitamin D that is a fat-soluble vitamin that is synthesized in skin under the influence of ultraviolet irradiation in sunlight. It is converted in the liver to 25-hydroxy-Vitamin D (calcifediol) and then into 1,25-dihydroxy-Vitamin D or calcitriol, the primary active form of vitamin D. Calcitriol functions as a hormone and with parathyroid hormone and calcitonin, regulates calcium and phosphate metabolism. Normal ion concentrations of calcitriol are essential for normal cardiovascular function, neuromuscular activity, mineralization of bone, cell differentiation, membrane structure, mitochondrial metabolism, pancreatic function, immunity, neural function, and other calcium-dependent processes.
|