Biosynthesis of vitamin B12: use of specific 13C-labelling for structural studies on factor IV

Abstract

I ,I 0,20-W3]Uro'gen Ill is unambiguously synthesised for enzymic conversion into precorrin-4 isolated after aerial oxidation as two epimers of Factor IV, the 13C NMR spectra of which rigorously confirm the presence of a C-I acetyl group in precorrin-4; attachment of the fourth methyl group at C-17 of precorrin-4 is also confirmed by related 1%-labelling experiments.

Biosynthesis of vitamin B12: the preparative multi-enzyme synthesis of precorrin-3A and 20-methylsirohydrochlorin (a 2,7,20-trimethylisobacteriochlorin)

“…These have been used as reconstituted multi-enzyme systems which are reasonably stable to biosynthesize, on what for this area is a large scale, complex intermediates involved in the biosynthesis of vitamin B "# . The methods described have proved invaluable for the preparation of non-labelled [46,47] and specifically labelled [44,45,[48][49][50] substrates for experiments that have led to important discoveries about the way the essential vitamin B "# is synthesized in living organisms [1,2].…”

“…When ALA or PBG are used as substrates for the coupledenzyme synthesis described in this paper, sets of at least eight or four labels respectively are introduced into the products. However, some experiments on B "# biosynthesis have required a single label or two labels at specific sites [44,45]. These were prepared from uroporphyrinogen III synthesized non-enzymically by routes tailored to the requirement for specific labelling.…”