Next Article in Journal
Synthesis and Liquid Crystalline Properties of New Diols Containing Azomethine Groups
Previous Article in Journal
Bohlmann-Rahtz Cyclodehydration of Aminodienones to Pyridines Using N-Iodosuccinimide
Previous Article in Special Issue
An Update on Vitamin E, Tocopherol and Tocotrienol—Perspectives
Molecules 2010, 15(5), 3228-3259; doi:10.3390/molecules15053228

Vitamin B12: Unique Metalorganic Compounds and the Most Complex Vitamins

* , ,  and
Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
* Author to whom correspondence should be addressed.
Received: 30 March 2010 / Revised: 27 April 2010 / Accepted: 28 April 2010 / Published: 30 April 2010
(This article belongs to the Special Issue Vitamins)
Download PDF [2029 KB, uploaded 18 June 2014]


The chemistry and biochemistry of the vitamin B12 compounds (cobalamins, XCbl) are described, with particular emphasis on their structural aspects and their relationships with properties and function. A brief history of B12, reveals how much the effort of chemists, biochemists and crystallographers have contributed in the past to understand the basic properties of this very complex vitamin. The properties of the two cobalamins, the two important B12 cofactors Ado- and MeCbl are described, with particular emphasis on how the Co-C bond cleavage is involved in the enzymatic mechanisms. The main structural features of cobalamins are described, with particular reference to the axial fragment. The structure/property relationships in cobalamins are summarized. The recent studies on base-off/base-on equilibrium are emphasized for their relevance to the mode of binding of the cofactor to the protein scaffold. The absorption, transport and cellular uptake of cobalamins and the structure of the B12 transport proteins, IF and TC, in mammals are reviewed. The B12 transport in bacteria and the structure of the so far determined proteins are briefly described. The currently accepted mechanisms for the catalytic cycles of the AdoCbl and MeCbl enzymes are reported. The structure and function of B12 enzymes, particularly the important mammalian enzymes methyltransferase (MetH) and methyl-malonyl-coenzymeA mutase (MMCM), are described and briefly discussed. Since fast proliferating cells require higher amount of vitamin B12 than that required by normal cells, the study of B12 conjugates as targeting agents has recently gained importance. Bioconjugates have been studied as potential agents for delivering radioisotopes and NMR probes or as various cytotoxic agents towards cancer cells in humans and the most recent studies are described. Specifically, functionalized bioconjugates are used as “Trojan horses” to carry into the cell the appropriate antitumour or diagnostic label. Possible future developments of B12 work are summarized.
Keywords: B12 structure-function; B12 enzymes; cobalamins; vitamin B12; B12 transport proteins B12 structure-function; B12 enzymes; cobalamins; vitamin B12; B12 transport proteins
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

Share & Cite This Article

Further Mendeley | CiteULike
Export to BibTeX |
EndNote |
MDPI and ACS Style

Randaccio, L.; Geremia, S.; Demitri, N.; Wuerges, J. Vitamin B12: Unique Metalorganic Compounds and the Most Complex Vitamins. Molecules 2010, 15, 3228-3259.

View more citation formats

Related Articles

Article Metrics

For more information on the journal, click here


[Return to top]
Molecules EISSN 1420-3049 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert