The biosynthesis of vitamin B12-like compounds

Abstract

In Escherichia coli 113-3 the requirement for "vitamin B12 " probably imposed by a defect in the synthesis of factor B, which represents the non-nucleotide portion of the molecule in several of the B12 vitamins (Gant et al. 1954). Given factor B, the microorganism can be directed to the synthesis of cyanocobalamin, factor A or pseudovitamin Bl2 by the pro-vision of the appropriate nucleotide or nucleotide base. For example, with adenine, pseudovitamin B12 is synthesized. A variety of compounds related in their chemical structure to adenine or to 5:6-dimethylbenziminazole were examined for their effect on "vitamin B12" synthesis in this system. In this way new "unnatural" analogues of vitamin B12 were obtained. Certain of these new analogues are active for Ochromonas malhamensis, an organism previously thought to be specific for cyanocobalamin. Certain other organisms, e.g. wild strains of E. coli and Aerobacter aerogenes, will produce these analogues when the appropriate intermediate is included in the growth medium.