Studies on the biosynthesis of riboflavin. 3. The utilization of 14C-labelled serine for riboflavin biosynthesis by Eremothecium ashbyii

Abstract

Uniformly labelled (C14) serine is incorporated into riboflavin by E. ashbyii to the extent of about 4-7%; incorporation is confined to positions 2 and 4a plus 9a; no activity was found in the aromatic ring or the ribityl side chain. About 13% of the label appears as carbon dioxide. (2-C ) Serine is incorporated almost exclusively into position 2; a small but definite labelling occurs in position 4a plus 9a but none in the aromatic ring. About 7% of the label appears as carbon dioxide. This isotope distribution is consistent with serine being converted into glycine and formate before incorporation into riboflavin. Adenine dilutes out markedly the incorporation of labelled serine into riboflavin, but has no effect on the amount of serine metabolized to carbon dioxide.