Biosynthesis of vitamin B12. Transformation of riboflavin deuterium-labeled in the 1'R position or 1'S position into 5,6-dimethylbenzimidazole
- Publication Type
- Journal contribution
- Authors
- Lingens, B.; Schild, T. A.; Vogler, B.; Renz, P.
- Year of publication
- 1992
- Published in
- Eur. J. Biochem.
- Band/Volume
- 207/3
- Page (from - to)
- 981-5
The 5,6-dimethylbenzimidazole moiety of vitamin B12 is formed from riboflavin in aerobic and some aerotolerant bacteria. Thereby C1' of riboflavin is transformed into C2 of the vitamin B12 base. In the present publication a study on this transformation with riboflavin 2H-labeled in the 1'R or 1'S position is described. This study was undertaken in order to find out if one of the two hydrogens at C1' is transferred to C2 of 5,6-dimethylbenzimidzaole. The 2H-labeled riboflavin samples were synthesized starting from unlabeled or 1-2H-labeled ribose and 3,4-dimethylaniline yieldin N-.beta.-D-ribopyranosyl-3,4-dimethylaniline. The unlabeled riboside was reduced to N-D-ribityl-3,4-dimethylaniline with sodium cyanoborotrideuteride, the 2H-labeled riboside with sodium cyanoborohydride. The ribityl derivs. were transformed into N-D-ribityl-2-phenylazo-4,5-dimethylaniline, and condensed with barbituric acid to riboflavin. The redn. of the ribosyl compd. to the ribityl deriv. is only partially stereospecific. Thus the riboflavin synthesized from unlabeled ribose had a 2H ratio of 3/1 (1'R/1'S), the riboflavin obtained from D-[1-2H1]ribose of 1/3 (1'R/1'S). The 2H content in these positions was detd. from the 1H-NMR spectra. These spectra showed also that 1 mol 2H/mol riboflavin was present in position 1'. The deuterated riboflavin samples were incubated under aerobic conditions with brokenThe 5,6-dimethylbenzimidazole moiety of vitamin B12 is formed from riboflavin in aerobic and some aerotolerant bacteria. Thereby C1' of riboflavin is transformed into C2 of the vitamin B12 base. In the present publication a study on this transformation with riboflavin 2H-labeled in the 1'R or 1'S position is described. This study was undertaken in order to find out if one of the two hydrogens at C1' is transferred to C2 of 5,6-dimethylbenzimidzaole. ...