For 10 points, name this B-complex vitamin that contains a central cobalt atom.
This vitamin is a co-factor in the conversion of methylmalonic acid to succinyl CoA, and along with folic acid, it is required for the conversion of homocysteine to methionine. Testing for high levels of methylmalonic acid or homocysteine is more sensitive than Schilling's test for diagnosing deficiency of this vitamin. The "methyl" form of this vitamin is the form used in the central nervous system, and is converted in the liver from a more common form. Gastric acid blockers may also inhibit production of intrinsic factor, which is necessary for this vitamin's absorption and is lacking in pernicious anemia. For 10 points, name this B-complex vitamin that contains a central cobalt atom.
This vitamin is a co-factor in the conversion of methylmalonic acid to succinyl CoA, and along with folic acid, it is required for the conversion of homocysteine to methionine.
Vitamin B12 [or cobalamin; accept cyanocobalamin or methylcobalamin]