CHEMICAL AND BIOCHEMICAL STUDIES OF VITAMIN B₁₂ AND ITS RELATED COMPOUNDS

XIII. COMPARISON OF AVAILABILITIES OF CYANOCOBALAMIN AND HYDROXOCOBALAMIN IN 5, 6-DIMETHYLBENZIMIDAZOLYCOBAMIDE COENZYME FORMATION BY PROPIONIBACTERIUM SHERMANII

Abstract

1. The difference was not observed in the effectiveness of hydroxocobalamin (OH-B₁₂) and cyanocobalamin (CN-B₁₂) as the precursor of 5, 6-dimethylbenzimidazolyl cobamide coenzyme (DBCC) by growing culture of Pr. shermanii cultivated for 8 to 10 days at 30°. But when DBCC was produced by the incubation of the precursor with washed cell suspension of the bacterium for 20 hours at 30°, OH-B₁₂ was quantitatively converted to DBCC, whereas CN-B₁₂, for the most past, remained unchanged.
2. The cause of the low conversion rate of CN-B₁₂ would be attributed to the small permeability or the less facility of transformation to DBCC or the combined effect of the two. In order to study this problem Pr. shermanii was cultivated for 9 days at 30° in the medium to which CN-B₁₂ or OH-B₁₂ had been added from the beginning of the culitivation or at an appropriate time in the incubation period and the amount and the form of the vitamin B₁₂ in the bacterial cells were investigated.
3. In the case of OH-B₁₂ most of the vitamin exogenously added on the 8th day was incorporated into the cells and transformed to DBCC as well as that added from the beginning of the incubation. On the other hand, the incorpoparion of CN-B₁₂ was lowered as the time of the addition was delayed.
4. In the cells grown in the presence of CN-B₁₂, only CN-B₁₂ and DBCC were detected and the presence of OH-B₁₂ was not ascertained. The fact may indicate that CN-B₁₂ is directly transformed to DBCC without changing to OH-B₁₂ or even if CN-B₁₂ is changed to OH-B₁₂, as an intermediate of the coenzyme, OH-B₁₂ would be immediately converted to DBCC.
5. From the results of this study it is not possible to conclude whether the formation of DBCC from CN-B₁₂ proceeds through OH-B₁₂ or not. However, it seems appropriate to conclude that either affinity to the bacterial cells or the conversion rate to DBCC of CN-B₁₂ is smaller than those of OH-B₁₂. It appears likely that the difference in the behaviors of OH-B₁₂ and CN-B₁₂ against bacterial cells is analogous to that against animal tissues.