The effects of certain purines and pyrimidines upon the production of riboflavin by Eremothecium ashbyii.

Eremothecium ashbyii is one of a number of organisms which produce considerable amounts of riboflavin, most of which is secreted by the cells into the medium (Guilliermond, 1935). The investigations of Schopfer (1944) and Schopfer and Guilloud (1945) resulted in the development of a synthetic medium for this organism which permitted growth and riboflavin production to occur under chemically defined conditions. Subsequent studies by Yaw (1948) have led to a modification of the original medium to iiZclude the amino acids, methionine and histidine. With the determination of the nutritional requirements of E. ashbyii, it became possible to undertake studies concerning the mechanism of riboflavin biosynthesis by means of precursors which modify riboflavin yield. Such an approach was utilized by Yaw (1948), who tested certain synthetic compounds for precursor activity. However, none of the compounds tested was found to be active in the biosynthesis of riboflavin. The present study is concerned with the purines and pyrimidines in the biosynthesis of riboflavin by E. ashbyii. These compounds were selected for the following reasons: (1) There are marked similarities in chemical structure among the purines, pyrimidines, and riboflavin, all of which contain a diazine ring, and (2) the purines and pyrimidines are naturally occurring compoun$ds. It was therefore hoped that the information obtained would provide a better understanding of riboflavin biosynthesis, about which very little is known at present (Williams et al., 1950).