[Studies on the biological function of the nucleotide base of vitamin B12].

Studies on the coenzyme activity of some nucleotide base analogues of adenosylcobalamine in the dioldehydratase and methyl-malonyl-CoA mutase systems resulted in fundamental differences: Contrary to dioldehydratase the coenzyme activity remains in the methyl-malonyl-CoA mutase system when adenosyl-cobamides with a strongly modified nucleotide base are studied. The analogues give a good growth response with Escherichia coli. In the growth test with Lactobacillus leichmanii only the cobamides that do not have substituted nucleotide bases in the positions 2 or 3 of their imidazole ring are active.