pantothenic acid and biotin fall 2011

pantothenic acid and biotin fall 2011 - Pantothenic Acid...

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Pantothenic Acid Name is derived from the Greek “pantos” which means everywhere. Present in almost every food item as Coenzyme A (CoA). This makes deficiencies virtually unheard of, except experimentally. Pantothenic Acid as isolated around 1931 by Dr. Robert Williams and the structure was Identified in 1939. However, F. Lipmann showed coenzyme A facilitated biological acetylation reactions He won a Nobel prize in 1957 for his work. Vitamin was once called vitamin B5 Discovery
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Sources Good sources: meats (liver), egg yolk , yeast , legumes, whole grains, potatoes, mushr broccoli, and avocados Also Royal jelly from bees. DRI (AI) Age mg/day 1-3 2 4-8 3 Males 9 – 13 4 14 - >70 5 Females 9 – 13 4 14 -> 70 5
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Fig. 9-17, p. 339 Structure Peptide bond
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Fig. 9-18, p. 340
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Absorption 85% of Pantothenic Acid found in food as CoA. CoA is hydrolyzed to release pantothenic acid. Pantothenic acid is absorbed primarily in jejunum. High concentrations: passive diffusion Low concentrations: sodium-dependent active multivitamin transporter/carrier (SMVT) (shares the carrier with biotin and lipoic acid) Absorption rate is 40 – 61% (mean 50%) Panthenol (alcohol form) found in multivitamins is converted to pantothenate: absorption decreases to 10% when vitamin level approaches 10 times DRI.
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Absorption continued From intestine, enter portal blood system, found free in blood. Uptake by tissues vary: heart, muscle, brain and liver: sodium-dependent active transpo other tissues – facilitated diffusion. In the cell most pantothenic acid is synthesized into CoA.
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Fig. 9-17, p. 339 Structure Rate limiting step adenylation
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CoA and 4’-phosphopantetheine function as carriers or transporters Of acetyl and acyl groups. Action of forming thio esters with carboxylic acids: Examples 1)Acetic acid (2 carbons) – acetyl group from pyruvate conversion 2) Malonic acid ( 3 carbons) – basis for synthesis of fatty acids (formed from acetyl CoA + CO 2 ). Malonyl CoA is joined to Acetyl CoA . 3) Propionic acid (3 carbons) – results from oxidation of the carbon skeleton of several amino acids and odd-chain fatty acids. 4) Methylmalonic acid (4 carbons) – formed as the next step from propionyl CoA (above driven by propionyl carboxylase. 5) Succinic acid (4 carbons) – an intermediate in the Krebs cycle.
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pantothenic acid and biotin fall 2011 - Pantothenic Acid...

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