A complex of cubilin and amnionless absorbs this vitamin. A biologically active form of this vitamin is abbreviated holoTC. This vitamin is a coenzyme for a reaction that accompanies the demethylation of methyltetrahydrofolate. Two important reactions for which it is a coenzyme are the conversion of methylmalonyl-CoA to succinyl-CoA and of homocysteine to methionine. Pancreatic proteases free this vitamin from haptocorrin. Autoimmune disorders that attack parietal cells 
A complex of cubilin and amnionless absorbs this vitamin. A biologically active form of this vitamin is abbreviated holoTC. This vitamin is a coenzyme for a reaction that accompanies the demethylation of methyltetrahydrofolate. Two important reactions for which it is a coenzyme are the conversion of methylmalonyl-CoA to succinyl-CoA and of homocysteine to methionine. Pancreatic proteases free this vitamin from haptocorrin. Autoimmune disorders that attack parietal cells can cause its deficiency because it must be bound to intrinsic factor in order to be absorbed in the ileum. The activity of this vitamin is due to the cobalt sitting at the center of its corrin ring, and its deficiency can lead to megaloblastic or pernicious anemia. For 10 points, name this B vitamin.
A complex of cubilin and amnionless absorbs this vitamin. A biologically active form of this vitamin is abbreviated holoTC.