SUMMARY

A purified preparation of the ‘amine ’ which accumulated in the medium during the growth of a strain of Saccharomyces cerevisiae (yeast 47) under conditions of partial biotin-deficiency contained two compounds, one of which was chromato-graphically and electrophoretically identical with synthetic 5-aminoimidazole. Both compounds gave identical colours on diazotization and coupling in the Bratton & Marshall reaction and on treatment with the Pauly imidazole reagent. The other, and major, component of purified ‘amine ’ was shown to be 5-aminoimidazole riboside by its conversion to the free base and ribose on incubation with a bacterial nucleosidase. Synthetic 5-aminoimidazole gave analytical figures for formate, NH,-N and total-N similar to those previously obtained for purified ‘amine’. Evidence was obtained that resting organisms of a mutant Escherichia coli converted ‘ amine ’ and synthetic 5-aminoimidazole to 5-amino-4-imidazole-carboxamide. One of the adenine derivatives which accumulated instead of ‘amine ’ and hypo-xanthine in a medium supplemented with aspartate was tentatively identified as t hiome t h yladenosine