MODE OF TRANSFORMATION OF [1-N-15]5-HYDROXYBENZIMIDAZOLE AND [1-N-15]5-HYDROXY-6-METHYLBENZIMIDAZOLE INTO THE 5,6-DIMETHYLBENZIMIDAZOLE MOIETY OF VITAMIN-B-12
B. Schulze et al., MODE OF TRANSFORMATION OF [1-N-15]5-HYDROXYBENZIMIDAZOLE AND [1-N-15]5-HYDROXY-6-METHYLBENZIMIDAZOLE INTO THE 5,6-DIMETHYLBENZIMIDAZOLE MOIETY OF VITAMIN-B-12, Biological chemistry Hoppe-Seyler, 375(11), 1994, pp. 785-788
The transformation of [1-N-15]5-hydroxybenzimidazole and [1-N-15]5-hyd
roxy-6-methylbenzimidazole into the 5,6-dimethylbenzimidazole moiety o
f vitamin B-12 by Eubacterium limosum-cultures was studied. The vitami
n B-12 obtained was exclusively N-15-labeled in N-1 of the base part,
as revealed by NMR-measurements. This indicates that either the unsubs
tituted 5,6-dimethylbenzimidazole presumably formed is not released fr
om the enzyme until the ribose-5'-phosphate substituent is introduced,
or that the precursors are first transformed into their alpha-nucleot
ide-5'-phosphates which then react to form lbenzimidazole-alpha-D-ribo
furanoside-5'-phosphate (alpha-ribarazole-5'-phosphate).