NUTR 3210 Lecture 9: MicronutrasEnzymeCofactors
4 Apr 2017
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Discovered by pellagra in humans and black tongue in dogs. High incidence where corn is the main dietary staple. Most fish, meats, breads, cereals, coffee and tea. Able to get 40% of rda in 100g of coffee. Trigonelline in coffee converted to niacin by heat. The higher the roasting heat the better. Predominantly as nicotinamide, nad, nadp (adenine dinucleotide phosphate) in animal foods. Predominant as nicotinic acid (provitamin) in plant foods. Can be produced in the liver using tryptophan (1/60) Nad and nadp hydrolyzed by glycohydrolase and release free nicotinamide to be. Absorbed a bit in stomach, mostly in si via facilitated transport. Cross cell membrane by diffusion except kidney and rbc. Niacin found primarily found as nicotinamide in plasma. Nicotinamide used to generate nad in all tissues. Once incorporated into nad and nadp, niacin is trapped in the cell. Both accept 2 electrons at a time. Over 100 enzymes require nad and nadp as coenzymes.
