Vitamin B12 is biosynthesised by many different organisms e.g. Pseudomonas denitrificans (aerobic) and Propionibacterium shermanii (essentially anaerobic, "microaerophilic"). The biosynthetic pathways in these two organisms show strong similarities but also some differences. Here we focus on the stages beyond the formation of the corrin macrocycle, about which there had earlier been conflicting reports.
A single cobyrinic acid diamide and a single triamide have been isolated from
Pr. shermanii and the diamide was shown to be the a,c-isomer. The triamide
is not the a,c,g-isomer but it is indistinguishable from the single triamide
isolated by other workers from Ps. denitrificans. Also Co-(5'-deoxy-5'-adenosyl)cobyrinic
acid a,c-diamide has been isolated and fully characterised and the deoxyadenosyl
derivative of the foregoing triamide has been shown to be present in the cells.
Department of Chemistry
University of Cambridge