Vitamin B and Related Compounds

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Abstract
Review with 248 references[long dash]The growing understanding of corrinoid chemistry will be the basis for a deeper knowledge of the biochemistry of these fascinating and unique substances of low molecular weight. It seems of the greatest importance, therefore, to show what influence changes in the corrinoid ligand system and in the axial ligands have on the reactivity of the molecule. Because they throw light on these problems, study of corrinoids of modified structure also leads to a better understanding of the biochemistry of B12. Investigations on the biosynthesis of the B12, molecule must snow not only how it is formed, but also why it must nave just this structure to perform its numerous biological functions. At least 9 different cell-free enzymatic reactions that are dependent on 5[image]-deaxyadenosyl-, ethyl-, or carboxymethylcorrinoids are now known. In some of these reactions, a reduced corrinoid with Col+ very probably functions as the active prosthetic group. Above all, the intramolecular double rearrangement, dependent on 5[image]-deoxyadenosylcobamide, is still mysterious. The importance to mammalian biochemistry of an understanding of vitamin Bj2 is increasing, since at least 2 of the enzymatic reactions dependent on corrinoid coenzymes occur in mammals including man. The ultimate goal would be the isolation in crystallized form of a corrinoid-contalning enzyme whose structural elucidation in 3 dimensions would make possible a thorough understanding of the intriguing set of reactions for which these coenzymes are required.