The effect of o-phenylenediamine on the biosynthesis of vitamin B12: a new vitamin B12 analogue

Abstract

Fermentations of Streptomyces griseus on a complex or a synthetic medium in the presence of o-phenylenediamine gave rise to the production of a new analogue of vitamin B12. The new substance was isolated in the form of red needles. Its absorption spectrum is practically identical with that of vitamin B12. Benziminazole was identified as a hydrolytic product. The new material is microbiologically (plate assay) more active than vitamin B12: the greater activity probably explains the apparently increased "vitamin B12" titres obtained by Dulaney and Williams (1953). The biosynthesis of true vitamin B12 is competitively inhibited by phenylenediamine. The biosynthesis of the new material in the presence of phenylenediamine is competitively inhibited by l:2-diamino-4:5-dimethylbenzene. The inhibition index lies somewhere between 160 and 320.