vitamin B-12

elevated homocysteine levels

increased risk for heart attack and stroke

treating B12 deficiency

inject directly into body, nasal gel

storage

liver

methylmalonyl mutase

metabolism of fatty acids with an odd number of carbons

formation of methionine from homocysteine

methyl donor

UL

none

foods

organ meats, fortified foods, meat, fish, poultry, dairy products

deficiency

pernicious anemia, neurological complications, elevated plasma homocysteine concentrations

B-12 in mouth

salivary glands produce R protein

B-12 in liver

stored

B-12 in ileum

vit/intrinsic factor absorbed into blood and binds to transport protein transcobalomin II

transport

blood transport protein transcobalamin II

absorption

bound to protein, HCl and pepsin in gastric juices release vitamin B-12, binds to R-protein, small intestine pancreatic protease enzymes release vitamin B-12 from R-protein

functions

formation of amino acid methionine, enzyme methylmalonyl mutase

B-12 in stomach

1. HCl and pepsin release vitamin B-12 bound to protein in food 2. free vitamin binds with R-protein 3. parietal cells secrete intrinsic factor

B-12 in small intestine

1. trypsin from pancreas releases 2. vit links with intrinsic factor

absorption location and %

50% in the ileum