Abstract
In a preceding paper the authors showed a marked increase in the contents of acid-soluble deoxyribosyl compounds as well as DNA in vitamin B_<12>-starved cells of Lactobacillus leichmannii when incubated with exogenously added cobalamins for 5 hours at 37℃. This paper deals with the study to determine a form of vitamin B_<12>-group compound occured in the bacterial cells during the incubation mentioned above, which seems to be an active form participating in the biosynthesis of deoxyribosyl compounds. The vitamin B_<12>-active substance in the cells was extracted with hot 80% ethanol and separated from a contaminating yellow substance by DEAE-cellulose column chromatography. The vitamin B_<12> contained in the passthrough fraction behaved similarly with DBCC in paper electrophoresis performed at pH 2.7 and 3.5. Its absorption spectrum and the changes by illumination as well as by cyanidetreatment were identical with those of DBCC. Furthermore its coenzyme activity was demonstrated to be almost the same as that of DBCC in Abeles・Lee's diol-dehydrase system. From these results it would be concluded that DBCC is the single form of the vitamin B_<12> in the cells of Lactobacillus leichmannii and it participates in the transformation of ribonucleotide (or ribonucleoside) to deoxyribonucleotide (or deoxyribonucleoside).
