The Many Faces of Vitamin B 12 : Catalysis by Cobalamin-Dependent Enzymes

• Published in: Annual review of biochemistry Vol. 72; no. 1; pp. 209 - 247
• Main Authors: Banerjee, Ruma, Ragsdale, Stephen W.
• Format: Journal Article
• Language: English
• Published: 01.06.2003
• ISSN: 0066-4154; 1545-4509
• DOI: 10.1146/annurev.biochem.72.121801.161828

▪ Abstract  Vitamin B 12 is a complex organometallic cofactor associated with three subfamilies of enzymes: the adenosylcobalamin-dependent isomerases, the methylcobalamin-dependent methyltransferases, and the dehalogenases. Different chemical aspects of the cofactor are exploited during catalysis by the isomerases and the methyltransferases. Thus, the cobalt-carbon bond ruptures homolytically in the isomerases, whereas it is cleaved heterolytically in the methyltransferases. The reaction mechanism of the dehalogenases, the most recently discovered class of B 12 enzymes, is poorly understood. Over the past decade our understanding of the reaction mechanisms of B 12 enzymes has been greatly enhanced by the availability of large amounts of enzyme that have afforded detailed structure-function studies, and these recent advances are the subject of this review.