Navigating the B12 road: Assimilation, delivery, and disorders of cobalamin

Abstract

The reactivity of the cobalt-carbon bond in cobalamins is the key to their chemical versatility, supporting both methyl transfer and isomerization reactions. During evolution of higher eukaryotes that utilize vitamin B 12, the high reactivity of the cofactor coupled with its low abundance pressured development of an efficient system for uptake, assimilation, and delivery of the cofactor to client B12-dependent enzymes. Although most proteins suspected to be involved in B12 trafficking were discovered by 2009, the recent identification of a new protein reveals that the quest for elucidating the intracellular B12 highway is still far from complete. Herein, we review the biochemistry of cobalamin trafficking. Copyright © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.