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ABSTRACT: Methionine, among the various additions to the medium, could only replace cobalt ion or vitamin B12 required for the growth of . It was demonstrated that there exists a vitamin B12-dependent terminal step in the methionine synthesis, that is, N5CH3-tetrahydrofolate-homocysteine transmethylase, which can also catalyze the methyl transfer from CH3B12 to homocysteine, in the cell-free extracts of Rhizobium meliloti. These facts seem to indicate that the vitamin B12-dependent pathway to methionine functions mainly among the B12-dependent enzymatic systems in the wild-type symbionts and this is the chief nutritional significance of cobalt.
Biochemical and Biophysical Research Communications 09/1974; 60(2):723–728. · 2.41 Impact Factor