PROPERTIES AKD DISTRIBUTIOiC’ OF VITAMIN B12r*

The existence of a new form of vitamin B,, in the feces of rats was first noted during a study of the effect of dietary cobalt on the growth of rats employed for vitamin Blz assay (1). When crude extracts of the feces ivere tested by the microbiological and rat assays, only a small fraction of the vitamin B,, activity measured microbiologically could be detected by the rat assay. Upon chromatographing the fecal extracts, a vitamin B,,active compound was detected that possessed an RF value intermediate between those of vitamins B12 and BIzb. Fractionation of the feces yielded a red compound that possessed growth-stimulating properties for Lactobacillus leichmannii but which failed to produce a growth response in the rat. For the sake of clarity when reference is made to the new compound, the notation vitamin Blzf (“f” = feces) has been tentatively assigned to the substance. While the paper referred to above was in press, Pfiffner et al. (2) reported the isolation of a vitamin BIz-like compound produced by an anaerobic microorganism obtained from rumen contents. The compound, designated pseudovitamin Blz, failed to support growth in the rat and chick but was active in this respect in L. Zeichmannii. Recently (3), the notation cyano-/I-cobalamin has been suggested for the substance. A comparison of the properties of vitamin B12f with those of pseudovitamin B12 suggests that the two compounds are identical. However, final judgment must await chemical degradation of vitamin B121 to determine its exact relationship to this and other known forms of vit,amin B12.