Riboflavin 3 pp - Riboflavin Spring 2011 History: Old...

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Unformatted text preview: Riboflavin Spring 2011 History: Old Yellow Enzyme • Warburg and Christian discovered physiological function of riboflavin coenzymes – enzyme-FAD complex referred to a “old yellow eznyme” due to bright yellow color Riboflavin Function Precursor of Flavin Coenzymes: FMN and FAD Major Dietary Riboflavin Sources: US • Meat, poultry, and fish – 1 serving beef provides 16% RDA – 1 serving fish provides up to 30% of RDA • Milk and dairy products – 1 quart milk = 100% RDA for adults • “Enriched” grain products Riboflavin Stability • Unstable to sunlight – Milk • Glass containers – 70% loss of riboflavin in 4 hrs • Opaque containers – Less riboflavin lost Riboflavin Absorption • Absorption – Dietary sources largely in form of coenzyme derivatives- must by hydrolyzed before absorbed – Upper small intestine by specialized mechanism involving phosphorylation-dephosphorylation rather than by passive diffusion – Process is sodium dependent and involves an ATPase active transport system that can be saturated Riboflavin Absorption • Absorption – Maximum transport capacity is ~25 mg – Delaying intestinal transit time of food may result in increase in amount absorbed – Consumption of food with riboflavin increases absorption – Bile acids increase absorption Transport and Excretion • Albumin: major transport protein • Immunoglobulins IgA, IgG, and IgM • Cellular uptake by riboflavin carrier Cellular uptake by riboflavin carrier mediated • Very little riboflavin stored • Urinary excretion- primarily intact riboflavin molecule not FAD FMN Riboflavin Function • Coenzymes widely distributed and catalyze numerous oxidation-reduction reactions • FAD is part of respiratory chain so riboflavin central to energy metabolism...
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This note was uploaded on 12/09/2011 for the course HUN 4445 taught by Professor Sitren during the Spring '08 term at University of Florida.

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Riboflavin 3 pp - Riboflavin Spring 2011 History: Old...

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