Abstract

76
F. Kiuchi, F. J. Leeper and A. R. Battersby
"Biosynthesis of Porphyrins and Related Macrocycles, Part 43. Isolation and Characterisation of Intermediates of Coenzyme B₁₂ Biosynthesis, a Cobyrinic Acid Triamide, the a,c-diamide and their Co-(5'-Deoxy-5'-adenosyl) derivatives, from Propionibacterium shermanii"
Chemistry & Biology,1995, 2, 527-532.

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.
Our results support a unique pathway in Pr. shermanii going forward from cobyrinic acid towards vitamin B₁₂, at least as far as the adenosylated triamide intermediate. No evidence was found for multiple alternative pathways.

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