Microbiological and Enzymatic Assays of Riboflavin Analogues

Abstract
A number of riboflavin analogues, most of them recently synthesized, were examined with respect to their abilities to replace or antagonize the utilization of riboflavin by Lactobacillus casei and with respect to their substrate activities with flavokinase which catalyzes phosphorylation of riboflavin. Diethyl-, 6-methyl-, and 2′-deoxyriboflavin were shown to serve as sole sources of flavin for the growing microbe and were found to be phosphorylated in the flavokinase system. D-Erythroflavin, 6,7-dihaloriboflavins, and other flavins substituted only in position 6 or 7 are poor replacers of riboflavin for growth. Certain of these latter analogues, for example, D-erythroflavin which is poorly phosphorylated and the dihaloriboflavins which are phosphorylated moderately well, act as antagonists at high concentrations in the presence of riboflavin. Other analogues which are inactive as either vitamins or substrates for flavokinase, but antagonize the utilization of riboflavin by inhibiting its conversion to flavin mononucleotide, include 2′,3′,4′-trideoxyriboflavin and 6-methyl-7-aminolumiflavin.

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