Enzymatic formation of ribityl side chain of riboflavin from ribose moiety of nucleotide precursor in Eremothecium ashbyii.

Reduction reaction of the ribose moiety of nucleotide precursor to the ribityl side chain of riboflavin, which is believed to be obligatory for riboflavin formation, was followed with crude enzyme from Eremothecium ashbyii. The reaction proceeded with the disappearance of NADPH in the presence of the nucleotides, GTP and ATP, in a Tris-HCl buffer (pH 7.5) at 37 degrees C. Chromatographic analysis of reaction products provides clear evidence that the reduction reaction of ribose to ribitol at the level of nucleotide (or nucleoside) and the cleavage reaction at carbon 8 on the purine ring occurred in the reaction mixture with enzymes from Eremothecium ashbyii.