The Biosynthesis of Vitamin B₁₂ Using ¹³C-labeling and NMR Techniques

Abstract

The biosynthesis of corrin was examined in a new light using ¹³C-labeling and NMR techniques which added a new dimension to the chemists' armamentarium and opened a new era in the study of the biogenesis of the complicated cobalamin. The use of ¹³C-FTNMR has led to the observation that 8 molecules of [2-¹³C] ALA are incorporated into vitamin B₁₂, [5-¹³C] ALA labels seven only of the carbon atoms cyanocobalamin, i.e. amino methyl groups of ALA is 'lost' the process. It has also been confirmed that seven of the methyl groups of B₁₂ are derived from [¹³CH₃] -methionine and further that the chirality of the gemdimethyl grouping at C₁₂ labelled with [¹³CH₃] -methionine is R. Four [8-¹³C] -PBG were incorporated into V.B₁₂ giving rise to 4 centers of enriched carbons. Mutiply-labelled uro'genIII (¹³C, ¹⁴C and ³H) has been used to show that incorporation takes place without randomization. A sequence for corrin synthesis from uro'genIII is presented. Also this review is shown more recently results in the corrin pathway.