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Walk the Even Hospital Database by book and chapter — the raw source passages that ground Ask, DDx, and the rest.
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©2013 UpToDate ® Print Email Role of cobalamin (vitamin B12) in homocysteine and methylmalonic acid metabolism Role of cobalamin in homocysteine and methylmalonic acid metabolism. Panel A - Methylcobalamin is a cofactor in the synthesis of methionine from homocysteine. Panel B - Adenosylcobalamin is a cofactor in the synthesis of succinyl-CoA from methylmalonyl-CoA. Tetrahydrofolate (THF) participates in homocysteine but not methylmalonic acid (MMA) metabolism. Thus, cobalamin deficiency is characterized by elevations in the serum levels of both homocysteine and MMA, while only homocysteine levels are elevated in folate deficiency. Reproduced with permission from Tefferi, A, Pruthi, RK. The Biochemical Basis of Cobalamin Deficiency. Mayo Clin Proc 1994; 69:181