Vitamin B12 (Cobalamin) Biochemistry
Vitamin B12 (cobalamin) is a water-soluble vitamin important in many metabolic reactions. Importantly, cobalamin serves as a cofactor for the enzymes methionine synthase and methylmalonyl-CoA mutase. It is particularly important in the nervous system for its role in myelin synthesis as well as in the bone marrow for the maturation of red blood cells. Cobalamin is primarily obtained from the diet in meat products, as it is synthesized by the gut bacteria in animals. Before cobalamin can be absorbed, however, parietal cells in the stomach must first secrete intrinsic factor. Intrinsic factor then binds to cobalamin, after which it can be absorbed in the terminal ileum.