Category: vitamin
Aliases: Methyl-B12, Activated B12, MeCbl
Pre-activated methyl-carrying form used directly by methionine synthase (remethylation of [[homocysteine]] → [[methionine]] (see [[methionine_sam_cycle]])). Does not cover mitochondrial methylmalonyl-CoA mutase — that requires [[adenosylcobalamin]], which cells synthesise from reduced cobalamins. Preferred by some authors in B12 deficiency with neurologic features, though head-to-head clinical superiority over [[cyanocobalamin]] is not established.