Vitamin B-6 choline

Vitamin B-6 choline - 1 Vitamin B-6, Choline NDFS 435...

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Unformatted text preview: 1 Vitamin B-6, Choline NDFS 435 Objectives Understand B-6 vitamers, digestion, absorption and transport Learn PLP active site mechanism Learn B-6 role in homocysteine metabolism Learn functions of choline 2 3 History of Vitamin B-6 1931 B-vitamin recognized that was separate from thiamin and riboflavin 1938 Vitamin characterized & synthesized Named pyridoxine 1945 Pyridoxal and pyridoxamine discovered All were interrelated Named vitamin B-6 4 History of Vitamin B-6 No specific human disease associated with Vitamin B-6 deficiency Associated with metabolism of protein, carbohydrates, and lipids Interactions with many vitamins and minerals Vitamin intrigues researchers 5 Vitamin B-6 Structures N C OO H C H 2 O H HO H 3 C 4-Pyridoxic acid (PA) N H C C H 2 OH H O H 3 C N CH 2 N H 2 CH 2 OH H O H 3 C N C H 2 OH C H 2 O H HO H 3 C 4 5 1 2 3 4 5 6 Pyridoxine (PN) Pyridoxal (PL) Pyridoxam ine (PM ) O 2 2 2 1 1 1 N HC C H 2 O PO 3- 2 HO H 3 C N CH 2 N H 2 CH 2 OPO 3-2 H O H 3 C N CH 2 O H CH 2 OPO 3-2 H O H 3 C O 3 3 Pyridoxine 5'-phosphate (PNP) Pyridoxal 5'-phosphate (PLP) Pyridoxamine 5'-phosphate (PMP) 1 pyridoxal kinase 2 alkaline phosphatase 3 PMP/PNP oxidase 4 aldehyde oxidase 5 pyridoxal dehydrogenase 6 Food Sources B-6 vitamers found in different foods Foods of plant origin: PN and PNP Whole grains, vegetables, bananas, nuts Foods of animal origin: PLP, PMP Meat, fish, chicken, Fortified cereals: PN, PNP, PN HCL Vitamin may be decreased in food by processing 7 Dietary Intake and Recommendations American intake Men: 2 mg/day Women: 1.5 mg/day People over 60 years M Men 1.5 mg; Women 1.0 mg/day 1998 RDA Adults, 19 50 years: 1.3 mg Adults, > 50 years: Men 1.7 mg/day; Women 1.5 mg/day UL 100 mg/day 8 Digestion, Absorption, & Transport Most B-6 in foods, naturally, is in the phosphorylated form. Alkaline phosphatase removes the phosphate (Zn requiring) PN, PL, PM rapidly absorbed (61-92%) Transported to liver, taken up by diffusion Metabolized primarily to PL and PLP (active coenzyme) Requires riboflavin as FMN Vitamers in systemic circulation PLP is bound to albumin PLP can be changed to PL by alkaline phosphatase PL may be bound to albumin, taken up into red cells, or transported into tissues (primarily muscle) Only PL can cross the plasma membranes Intestine...
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Vitamin B-6 choline - 1 Vitamin B-6, Choline NDFS 435...

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