Studies on biological functions of 5'-methylthioadenosine vitamin B12-replacing effect for Ochromonas malhamensis

An unidentified factor which can completely replace the vitamin B12 requirement of a protozoan, Ochromonas malhamensis, was found in commercial yeast extract powder. The factor showed a positive sugar test with orcinol reagent. The presence of sulfur was demonstrated with platinic iodide reagent. The molecular weight, 297, and the chemical formula, C11H15O3N5S, were determined by mass spectrometry and elemental analysis. Infra-red and nuclear magnetic resonance studies indicated the presence of a thiomethyl group. The factor was hydrolyzed by treatment with acid into adenine and 5-methylthioribose, i.e., the sugar constituent of 5'-methylthioadenosine. The factor was identified as 5'-methylthioadenosine from the behavior exhibited in thin-layer chromatography and from microbiological tests for its vitamin B12-replacing effect.