BIOSYNTHESIS OF RIBOFLAVINE BY A PURINE-REQUIRING MUTANT STRAIN OF ESCHERICHIA COLI

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Abstract
Riboflavine biosynthesis occurs in non-proliferating cultures of a purine-requiring strain of E. coli (ATCC no. 13863). No significant incorporation of radioactivity from [1-I4c]glycine into either C-4a and C-9a of riboflavine or into nucleic-acid purines is detected under the above conditions; appre-ciable incorporation of label into 5-aminoimidazole-4-carboxamide occurs. However, the label of [6-14c]guanine is incorporated significantly into C-4 of riboflavine and into nucleic acid adenine and guanine; the specific radioactivity of the riboflavine is approximately twice that of either adenine or guanine of nucleic-acid. Those results show that a purine derivative is an obligatory intermediate in riboflavine biogenesis.