Biosynthesis of vitamin B12 from CO60-labeled cobalt-porphyrin by aged cell homogenate of Euglena gracilis.

1. Biosynthesis of vitamin B12 by aged cell homogenate of B12-nonproducing microbe was tested, and it was found by bioautography that the in vitro formation of vitamin B12 from cobalt-porphyrin and 5, 6-dimethylbenzimidazole was always positive.2. Further evidence was obtained by using Co60-labeled Co-porphyrin, and biosynthesis of Co60-labeled vitamin B12 was confirmed by radioautography.3. From these findings it is concluded that cobalt-porphyrin may be available for the formation of vitamin B12 in vitro by the intracellular enzyme of an Euglena strain which is ordinarily an nonproducer of vitamin B12.