B12 Coenzymes Are Associated with Rearrangements on Adjacent Carbon Atoms

Vitamin B12 Coenzymes Are Associated with Rearrangements on Adjacent Carbon Atoms 

The principal coenzymatic form of vitamin B12 is 5 -deoxyadenosylcobalamin, the structural formula of which is given in figure 10.17. The structure includes a cobalt - 

The vitamin was discovered in liver as the antipemi-cious anemia factor in 1926, but discovery of its complete structure had to await its purification, chemical characterization, and crystallization, which required more than 20 years. Even then the determination of such a complex structure proved to be an elusive goal by conventional approaches of that day and had to await the elegant x-ray crystallographic study of Lenhert and Hodgkin in 1961, for which Dorothy Hodgkin was awarded the Nobel Prize in 1964. 

Most 5 -deoxyadenosylcobalamin-dependent enzy-matic reactions are rearrangements that follow the pattern of equation (21), in which a hydrogen atom and another group 

Structure of 5 -deoxyadenosylcobalamin coenzyme (vitamin Bj2). The reactive groups are shown in red. 

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Ascorbic Acid Is Required to Maintain the Enzyme that Forms Hydroxyproline Residues in Collagen Vitamin B12 Coenzymes Are Associated with Rearrangements on Adjacent Carbon Atoms Iron-Containing Coenzymes Are Frequently Involved in Redox Reactions Metal Cofactors Lipid-Soluble Vitamins... 

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