A DERANGEMENT IN B12 METABOLISM LEADING TO HOMOCYSTINEMIA CYSTATHIONINEMIA AND METHYLMALONIC ACIDURIA

In mammals, vitamin B12 derivatives are known to function as coenzymes for two reactions: (a) methionine formation from 5-methylfolate-H4 and homocysteine and (b) isomerization of methylmalonyl-CoA to succinyl-CoA (Weissbach and Dickerman,1967; Hogenkamp, 1968). We have recently investigated an infant with abnormalities of both the sulfur amino acids and methylmalonic acid. This paper summarizes the results of our investigation which indicate the occurrence of a hitherto unrecognized metabolic abnormality, a defective ability to accumulate the coenzymatically active derivatives of B12. As far as we are aware, this is the first proven instance of deranged vitamin metabolism in a human. © 1969.