Open AccessThe Biosynthesis of Vitamin B 12 : A Study by 13 C Magnetic Resonance Spectroscopy
Author(s) -
C. E. Brown,
Joseph Katz,
David Shemin
Publication year - 1972
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.69.9.2585
Subject(s) - chemistry , corrin , resonance (particle physics) , methyl group , nuclear magnetic resonance spectroscopy , chemical shift , spectroscopy , ring (chemistry) , nuclear magnetic resonance , proton , crystallography , stereochemistry , group (periodic table) , physics , atomic physics , organic chemistry , quantum mechanics
The origin of the methyl group on C-1 of Ring A of the corrin ring of vitamin B12 was investigated by13 C magnetic resonance spectroscopy. The proton-decoupled13 C spectra of vitamin B12 synthesized from [5 -13 C]δ-aminolevulinic acid byPropionibacteria were obtained by Fourier-transform nuclear magnetic resonance of high resolution, and spectra of high-resolution proton magnetic resonance of the13 C-labeled B12 were also taken. The δ-carbon atom of δ-aminolevulinic acid is the source of seven or eight known positions of vitamin B12 , depending on whether the C-1 methyl group is also derived from the labeled substrate. We have found seven resonances whose chemical shifts enable us to identify the position of the13 C atoms in the molecule from the assignment of Dodderell and Allerhand. We observed no13 C resonance corresponding to the C-1 methyl group of Ring A. Furthermore, the proton magnetic resonance spectrum showed no spin-spin splitting of the proton peak at the τ values assigned for the H atoms in this methyl group. It would thus appear that the methyl group at C-1, which has been considered to have the same origin as the δ-methine bridge of porphyrins, does not originate from the δ-carbon atom of δ-aminolevulinic acid. This finding may aid in elucidation of the mechanism of synthesis of the functional isomer of vitamin B12 and porphyrins. The13 C-labeled vitamin B12 enabled us to make further assignments to the13 C magnetic resonance of the vitamin.