1pp Vitamin K 11 - Vitamin Vitamin K Spring 2011 Vitamin K...

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Vitamin K Spring 2011
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Vitamin K Deficiency: Hemorraghing Animal Model • Danish discovery • Fat-free diets led to hemorraghing:chickens –Fat soluble factor named vitamin K –1943 Nobel Prize in hysiology and Medicine Physiology and Medicine
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Menadione Phylloquinone enaquinone (MK ) enaq inone +1 Menaquinone-4 (MK-4) Menaquinone n+1
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itamin K: Nomenclature Vitamin K: Nomenclature • Quinones hylloquinone rovides most in US –Phylloquinone (provides most in US diet) lant sources • plant sources – green leafy vegetables and vegetable oils
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Vitamin K: Nomenclature enaquinone • Menaquinone • Animal sources • Intestinal bacteria – E. coli, B. fragilis K is unique to the enaquinones • MK-4 is unique to the menaquinones – Alkylated from menadione present in animal feed lso product of tissue conversion from dietary – Also product of tissue conversion from dietary phyloquinone
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itamin K: Absorption Vitamin K: Absorption • ~80% absorbed (synthetic) • Food bioavailability much lower than synthetic
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Vitamin K: Absorption –Small intestine –jejunum nhanced by fat bile salts Enhanced by fat, bile salts, pancreatic juice icelles –Micelles –Chylomicrons lymph
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itamin K: Absorption Vitamin K: Absorption • Large intestine sident icroflora –resident microflora synthesize & secrete menaquinone –absorption from colon limited
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Vitamin K Malabsorption • Absorption can be dramatically reduced in clinical conditions – Pancreatic insufficiency – Biliary insufficiency – Celiac disease
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itamin K: Transport Vitamin K: Transport • Chylomicron remnants deliver itamin K to the liver vitamin K to the liver • Transport in lipoproteins: HDL, LDL, VLDL ,, –very low blood concentrations 15 15ng/m l • 0.15 -1.15 ng/ml
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Vitamin K Cellular Uptake • Tissue uptake would occur when chylomicron remnants are “cleared” by apolipoprotein E (apoE) receptors
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Vitamin K Storage, Excretion •Storage –Liver: predominately as menaquinone –Limited storage (50-100 μ g) apid turnover ort half e –Rapid turnover- short half-life •Body pool turnover in ~1.5 days • Excretion: feces, urine
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itamin K Function Vitamin K Function • Blood clotting and bone mineralization –vitamin K facilitates γ - rboxyglutamatic acid (Gla) carboxyglutamatic acid (Gla) formation roteins required for normal blood p o qu d o o a b ood clotting and bone mineralization
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itamin K Function Vitamin K Function • Cofactor for a specific carboxylase –catalyzes the γ -carboxylation of peptide-bound glutamyl residues • Posttranslational carboxylation ecific l mic cid residues in –specific glutamic acid residues in proteins rms rboxyglutamic cid ( la –forms γ -carboxyglutamic acid (Gla)
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Vitamin K Dependent Carboxylase Exact function of Vitamin K in this reaction still being investigated. • Vitamin K hydroquinone and
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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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1pp Vitamin K 11 - Vitamin Vitamin K Spring 2011 Vitamin K...

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