Biosynthesis of Riboflavin

A riboflavin-deficient mutant of Saccharomyces cerevisiae accumulates 2,5-diamino-6-hydroxy-4-(1'-d-ribitylamino)pyrimidine. The labile substance was reacted with diacetyl prior to isolation, yielding 2-amino-6,7-dimethyl-4-oxo-8-(1'-d-ribityl)-4,8-dihydropteridine. This compound was isolated, purified, and identified by chromatographic and spectrometric procedures. Furthermore, 2-amino-4-hydroxy-6-hydroxymethylpteridine and 2,6-diamino-4-hydroxypteridine were isolated from the culture fluid of the mutant. 2,5-Diamino-6-hydroxy-4-(1'-d-ribitylamino) pyrimidine or a phosphoric ester of this compound appears to be an intermediate in the biosynthesis of riboflavin.