Abstract

24
H. C. Uzar, A. R. Battersby, T. A. Carpenter and F. J. Leeper
"Biosynthesis of Porphyrins and Related Macrocycles, Part 28. Development of a Pulse Labelling Method to Determine the C-Methylation Sequence for Vitamin B₁₂"
J. Chem. Soc., Perkin Trans. 1, 1987, 1689-1696. Full Text

The biosynthesis of vitamin B₁₂ involves enzymic C-methylation of uroporphyrinogen-lII at 8 sites. Earlier work had established that the first 3 methyl groups are introduced at positions 2,7, and 20 in that order. Pulse-labelling experiments with ¹³C-labelled and unlabelled S-adenosylmethionine show that the remaining 5 C-methyl groups are added in the order 17, 12, 1, 15, 5. The pulse labelling approach depends on assaying the biosynthetic product for extent of ¹³C-labelling by n.m.r.
The results lead to discussion of the late stages of the B₁₂ biosynthetic pathway. This highlights the need for a simple scheme of nomenclature for the various biosynthetic intermediates and a systematic one based on the parent names precorrin and corrin is proposed.

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